[top]
000
FXUS65 KTFX 230020
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
515 PM MST SUN NOV 22 2009
UPDATED AVIATION DISCUSSION
.DISCUSSION...
TONIGHT THROUGH TUESDAY...A VIGOROUS UPPER LEVEL TROF CONTINUES TO
TRACK EAST ACROSS THE NORTHERN ROCKIES THIS AFTERNOON AND IS
EXPECTED TO CONTINUE EAST ACROSS THE STATE TONIGHT WITH A RIDGE OF
HIGH PRESSURE BUILDING IN ITS WAKE ON MONDAY. MOIST AND UNSTABLE
WESTERLY FLOW ALOFT WILL SHIFT TO THE NW AS THE TROF AXIS SHIFTS
EAST ACROSS THE REGION TONIGHT. UPPER LEVEL JET DYNAMICS
ASSOCIATED WITH THE TROF WILL TRACK BY TO THE SOUTH OF THE
FORECAST AREA THIS EVENING AND THIS WILL CONTINUE TO KEEP THE BEST
CHANCE FOR SNOW OVER SW MT ZONES THROUGH THIS EVENING. WINTER
WEATHER ADVISORY FOR GALLATIN AND MADISON COUNTIES CONTINUES THROUGH
11PM MST...WHERE BEST LIFT IN ASSOCIATION WITH THE TROUGH WILL
COMBINE WITH MOIST AND UNSTABLE WEST TO NW FLOW ALOFT AND
OROGRAPHIC ENHANCEMENT TO PRODUCE SEVERAL MORE INCHES OF
ADDITIONAL ACCUMULATION THROUGH THIS EVENING. WESTERLY DOWNSLOPE
FLOW WILL LIMIT PRECIPITATION TO ISOLATED SNOW SHOWERS AT BEST FOR
MUCH OF THE NORTH CENTRAL MT PLAINS. SNOW SHOWERS WILL GRADUALLY
DIMINISH AFTER MIDNIGHT AS THE TROF TRACKS EAST OF THE FORECAST
AREA. UPPER LEVEL RIDGE BUILDS IN ON MONDAY FOR DRIER CONDITIONS
WITH TEMPS REMAINING NEAR SEASONAL AVERAGES. THE NEXT DISTURBANCE
IN WESTERLY FLOW TRACKS INTO WESTERN CANADA MONDAY NIGHT AND
ACROSS SOUTHERN ALBERTA ON TUESDAY. THE NORTHERLY TRACK OF THIS
SYSTEM WILL KEEP PRECIPITATION CHANCES MINIMAL...EXCEPT FOR SOME MTN
SNOW SHOWERS. MAIN IMPACT WILL LIKELY BE STRONG WINDS...ESPECIALLY
ALONG THE ROCKY MTN FOR A PERIOD ON TUESDAY AND HIGH WIND HIGHLIGHTS
MAY BECOME NECESSARY. HOENISCH
TUESDAY NIGHT THROUGH SUNDAY NIGHT...BOTH THE ECMWF AND GFS
COMPUTER MODEL RUNS ARE IN GOOD AGREEMENT INTO FRIDAY BUT DIVERGE
WITH THEIR SOLUTIONS THEREAFTER. FOR TUESDAY NIGHT A STRONG UPPER
RIDGE WILL BE APPROACHING THE AREA. THERE COULD BE A FEW SNOW
SHOWERS WITH LINGERING MOISTURE IN THE NORTHWEST FLOW ALOFT. THE
STRONG UPPER RIDGE WILL BE OVER THE AREA WEDNESDAY AND THURSDAY
FOR GENERALLY DRY CONDITIONS WITH TEMPERATURES WELL ABOVE NORMAL
OVER THE PLAINS. RAISED HIGH TEMPERATURES FOR THANKSGIVING 5 TO
10 DEGREES OVER THE PLAINS. IN FACT HIGH TEMPERATURES APPROACHING
RECORD LEVELS ARE NOT OUT OF THE QUESTION. AN UPPER TROUGH IS
FORECAST TO MOVE INTO THE AREA FRIDAY NIGHT AND MODELS HAVE COME
INTO BETTER AGREEMENT ON THE TIMING OF THIS FEATURE. AS THE UPPER
TROUGH MOVES INTO THE AREA EXPECT INCREASING CHANCES OF
PRECIPITATION ALONG WITH COOLER TEMPERATURES. AS WAS MENTIONED
BEFORE MODELS DIFFER LATER IN THE WEEKEND INTO EARLY NEXT WEEK.
INHERITED CHANCES OF PRECIPITATION LOOK REASONABLE AS THEY ARE A
COMPROMISE BETWEEN THE DRIER ECMWF RUN AND THE WETTER GFS RUN.
BLANK
&&
.AVIATION...
UPDATED 1735Z.
AN UPPER LEVEL LOW CONTINUES TO MOVE THROUGH SOUTHWESTERN MONTANA.
THIS STORM SYSTEM WILL CONTINUE TO AFFECT THE REGION THROUGH 14Z
MONDAY. EXPECT MOUNTAINS TO BE OBSCURED...ALONG WITH SCATTERED SNOW
SHOWERS...MAINLY SOUTH OF A LINE FROM HELENA TO LEWISTOWN. IFR
CONDITIONS CAN BE EXPECTED AT TIMES IN THIS REGION. MAINLY MID/HIGH
LEVEL CLOUDINESS CAN BE EXPECTED OVER NORTH CENTRAL MONTANA UNTIL
14Z MONDAY...THEN GENERALLY CLEARING SKIES CAN BE EXPECTED FOR THE
REMAINDER OF THE PERIOD...WITH VFR CONDITIONS PREVAILING. BRUSDA
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 43 31 48 / 20 0 10 10
CTB 25 42 30 44 / 10 0 10 10
HLN 22 41 25 44 / 50 10 10 20
BZN 17 36 10 39 / 70 10 0 20
WEY 12 28 7 32 / 90 30 20 20
DLN 16 33 14 38 / 50 10 0 10
HVR 21 47 25 48 / 10 0 10 10
LWT 19 40 24 45 / 40 10 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR MTZ015-
055.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...COULSTON
AVIATION...BRUSDA
WEATHER.GOV/GREATFALLS
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000
FXUS65 KBYZ 222224
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
324 PM MST SUN NOV 22 2009
.SHORT TERM...VALID FOR MON AND TUE...
COMPACT BUT POTENT UPPER LEVEL SYSTEM MOVING ACROSS THE IDAHO
PANHANDLE FILLING AS IT HEADS TOWARDS MONTANA LATE THIS AFTERNOON.
THIS FEATURE IS SPREADING SOUTHWEST FLOW ALOFT AND WEAK DIFFLUENCE
ACROSS THE AREA WITH THE MOST IMPORTANT FEATURE STEEPENING LAPSE
RATES DUE TO COLD AIR ALOFT. SOME SNOW SHOWERS HAVE ALREADY MOVED
THROUGH THE AREA AND ACCUMULATIONS NOTED ON ROADWAYS WEST OF LVM
WITH IR IMAGERY SHOWING ANOTHER BATCH OF COOLING CLOUD TOPS OVER
WEST CENTRAL MONTANA. EXPECT SUPPORT FOR SNOW SHOWERS TO INCREASE
AND AS ENERGY BEGINS TO SPLIT WITH A PIECE DIVING INTO WYOMING
THIS WILL FAVOR SHOWERS SLOWING DOWN IN SPEED AND SETTING UP OVER
PARK COUNTY FOR THE NEXT 6 HOURS. WITH INSTABILITY LOOKING PRETTY
GOOD WOULD EXPECT RAPID ACCUMULATIONS FOR A COUPLE OF HOURS AND
WILL CONTINUE WINTER WEATHER ADVISORY UNTIL MIDNIGHT FOR THE NON
MOUNTAIN ZONES OF PARK COUNTY ESPECIALLY WITH SUNSET HELPING
ENSURE SNOW STICKS. SYSTEM COMING ACROSS SHOULD ALSO ALLOW WINDS
TO WEAKEN A BIT OVER GAP FLOW AREAS. FOCUS SHIFTS A BIT LATER INTO
SOUTH CENTRAL MONTANA AND NORTH CENTRAL WYOMING WITH MID LEVEL
FLOW BECOMING NORTHWESTERLY. LOOKS LIKE BIG HORNS WILL HAVE A
CHANCE FOR A QUICK ACCUMULATION LATER TONIGHT AND HAVE PUT
ACCUMULATIONS UP TO 5 INCHES INTO THE MOUNTAINS. MONDAY THE UPPER
LEVEL LOW REACHES WESTERN SOUTH DAKOTA AND AIRMASS BEGINS TO
STABILIZE FROM WEST TO EAST. EXPECT SOME ISOLATED SHOWER ACTIVITY
TO CONTINUE OVER THE MOUNTAINS WITH FLOW ALOFT SUPPORTING
OROGRAPHICS AND OVER SOUTHEAST MONTANA WHERE COLDEST AIR ALOFT
WILL LINGER. SHOULD CONTINUE TO BE COOL DESPITE CLEARING SKIES AND
WILL HAVE TO SEE IF ANY WESTERN ZONES ACCUMULATE ENOUGH SUNSHINE
TO RESIST LIMITED DAYTIME HEATING. UPPER LEVEL RIDGE MOVING INTO
THE PACIFIC NORTHWEST LATE IN THE DAY WITH A SHORTWAVE MOVING INTO
BC SETTING UP ANOTHER PATTERN FAVORING GAP FLOW WINDS MONDAY NIGHT
INTO TUESDAY MORNING. HAVE RAISED WINDS TO SUB ADVISORY CRITERIA
AS INITIALLY PRESSURE GRADIENTS ARE A BIT MORE WESTERLY BUT THEY
TIGHTEN RIGHT AROUND 12Z TUESDAY AND BECOMING MORE SOUTHWESTERLY
FOR A 6 HOUR PERIOD. WITH UPPER RIDGE TILTING INTO THE AREA MONDAY
NIGHT INTO TUESDAY LOOKS DRY AND NEXT FOCUS BECOMES A CLIPPER
FRONT THAT MOVES ACROSS THE AREA TUESDAY AFTERNOON. TIGHTER
PRESSURE GRADIENTS AND MID LEVEL MOMENTUM LOOK TO WAIT TO IMPACT
SOUTHEAST MONTANA TUESDAY EVENING AND THIS MAY KEEP WINDS FROM
BECOMING TOO STRONG. FRONTAL PASSAGE LOOKS PRETTY DRY BUT KEPT
MENTION OF SOME SHOWERS AS IT PRODUCES A BIT OF UPSLOPE INTO THE
HIGHER TERRAIN SOUTHEAST OF BILLINGS. TEMPERATURES LOOK BE WARMER
ON TUESDAY WITH LESS CLOUDS AND A BIT OF COMPRESSIONAL WARMING.
BORSUM
.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...
UPPER LEVEL RIDGE WILL BUILD INTO THE AREA ON WEDNESDAY AND
THURSDAY BRINGING DRY CONDITIONS AND SLIGHTLY WARMER
TEMPERATURES. HAVE CONTINUED TO KEEP THINGS DRY AND HAVE NOT
CHANGED ANYTHING FOR THESE PERIODS. UPPER LEVEL TROUGH WILL MOVE
INTO THE REGION FRIDAY NIGHT AND SATURDAY AND BRING ANOTHER
CHANCE OF PRECIPITATION AND COOLER TEMPERATURES. THE ECMWF IS A
LITTLE DIFFERENT WITH THE SOLUTION AS IT CUTS OFF A LOW OVER THE
FOUR CORNER REGION WHERE THE GFS KEEPS ALL THE ENERGY OVER THE
FORECAST AREA. EITHER SOLUTION WOULD BRING A CHANCE OF PRECIP SO
HAVE KEPT THE POPS GOING EVERYWHERE. ECMWF DRIES THINGS OUT BY
SUNDAY WHERE THE GFS KEEPS AN UNSETTLED NORTHWEST FLOW OVER THE
AREA. HAVE PUT IN SOME CLIMO POPS FOR THIS PERIOD GIVEN THE
UNCERTAINTY FOR NOW. SOLUM
&&
.AVIATION...
CLOUDS WILL CONTINUE TO INCREASE FROM WEST TO EAST TONIGHT AS A
STORM SYSTEM MOVES INTO THE AREA. SNOW WILL ALSO CONTINUE TO
INCREASE FROM WEST TO EAST THROUGH TONIGHT. EXPECT MOUNTAIN
OBSCURATIONS AND MVFR CONDITIONS AS THE SNOW MOVES ACROSS.
LOCALIZED IFR CONDITIONS WILL ALSO BE POSSIBLE. GUSTY WINDS WILL
ALSO CONTINUE ACROSS MUCH OF THE AREA THROUGH THIS EVENING. SOLUM
&&
.PRELIMINARY POINT TEMP/POPS...
MON TUE WED THU FRI SAT SUN
-----------------------------------------------------------
BIL 025/040 028/047 030/047 030/055 032/055 033/046 026/042
41/B 00/B 10/B 00/U 00/B 22/W 02/J
LVM 021/034 026/042 027/048 026/054 030/050 026/041 020/040
82/J 00/N 10/B 00/U 02/W 32/W 02/J
HDN 024/043 021/049 028/048 027/056 026/056 030/049 022/045
42/J 00/B 10/B 00/U 00/B 22/W 02/W
MLS 025/043 022/048 024/044 024/053 026/055 032/047 024/042
22/J 00/B 20/B 00/U 00/U 22/W 02/J
4BQ 024/040 019/046 021/043 023/052 026/055 030/047 021/042
22/W 00/B 20/B 00/U 00/U 22/W 02/J
BHK 022/040 019/044 020/040 020/051 028/052 029/046 022/041
22/W 01/B 20/B 00/U 00/U 22/W 02/J
SHR 023/038 015/047 021/046 023/054 024/055 025/046 019/042
52/J 00/B 30/B 00/U 00/B 22/W 02/J
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT MST TONIGHT
FOR ZONES 40-64-65.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
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000
FXUS65 KMSO 222142
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
242 PM MST SUN NOV 22 2009
.DISCUSSION...AN UPPER LEVEL TROUGH AND ASSOCIATED JET STREAM WILL
CONTINUE TO INFLUENCE THE NORTHERN ROCKIES THIS EVENING AND
OVERNIGHT. THE FIRST BATCH OF PRECIPITATION FROM THIS MORNING HAS
MOVED EAST OF THE CONTINENTAL DIVIDE AND LEFT MUCH OF WESTERN
MONTANA AND NORTH CENTRAL IDAHO IN A BRIEF LULL. HOWEVER...AS THE
UPPER JET PUSHES THROUGH THE REGION THIS AFTERNOON...ANOTHER
ROUND OF SNOW SHOWERS IS EXPECTED. THE MAIN FOCUS OF THIS ACTIVITY
IS EXPECTED TO REMAIN GENERALLY OVER NORTH CENTRAL IDAHO AND ALONG
THE IDAHO/MONTANA BORDER. WITH SNOW LEVELS DOWN TO ALL BUT THE
LOWEST VALLEY FLOORS...EXPECT ACCUMULATING SNOW TO CONTINUE INTO
THIS EVENING OVER THE AFOREMENTIONED AREAS. IN ADDITION...GUSTY
SOUTHWEST TO WEST WINDS WILL CAUSE LOCAL AREAS OF BLOWING AND
DRIFTING SNOW...CAUSING HAZARDOUS DRIVING CONDITIONS IN LOW
VISIBILITY. SEVERAL WINTER WEATHER ADVISORIES REMAIN IN
PLACE...PLEASE SEE WWW.WEATHER.GOV/MISSOULA FOR FURTHER INFORMATION.
THE MAIN UPPER TROUGH WILL SHIFT EAST OF THE CONTINENTAL DIVIDE
OVERNIGHT TONIGHT...LEAVING NORTHWESTERLY FLOW ALOFT OVER THE
NORTHERN ROCKIES. THIS FLOW REGIME WILL USHER A FEW WEAK
DISTURBANCES THROUGH THE FLOW AND ALLOW FOR THE CONTINUATION OF
LIGHT SHOWERS THROUGH MONDAY. THE SHOWERS MAY BECOME BANDED IN
NATURE BY TOMORROW MORNING.
MONDAY NIGHT THROUGH THURSDAY NIGHT...A FAST MOVING PACIFIC STORM
SYSTEM IS ANTICIPATED TO GRAZE NORTHWEST MONTANA BETWEEN MONDAY
NIGHT AND TUESDAY MORNING. THE MOST SIGNIFICANT STORM FEATURES ARE
EXPECTED TO REMAIN NORTH OF THE CANADIAN BORDER...HOWEVER UNSTABLE
NORTHWESTERLY FLOW AT RIDGETOP WILL LIKELY DEVELOP IN THE WAKE OF
THIS SYSTEM. THE INSTABILITY WILL KEEP SNOW SHOWER ACTIVITY MAINLY
LOCKED ON THE HIGH TERRAIN OF NORTHWEST MONTANA AND NORTH CENTRAL
IDAHO. BY TUESDAY EVENING...HIGH PRESSURE WILL BECOME THE DOMINANT
WEATHER FEATURE PRESENT ACROSS THE NORTHERN ROCKIES...WITH
PRECIPITATION CHANCES DIMINISHING RAPIDLY THEREAFTER. VALLEY
INVERSIONS WILL STRENGTHEN FROM TUESDAY NIGHT THROUGH
THURSDAY...WITH RIDGETOPS AND MID SLOPES WARMING RAPIDLY.
CONSIDERING RESIDUAL MOISTURE AND SNOW COVER EXPECTED TO BE
PRESENT...FOG IS POSSIBLE WITHIN AREA VALLEYS DURING WEDNESDAY AND
THURSDAY MORNINGS. LOW LEVEL MIXING WILL INCREASE BY THURSDAY
EVENING AND ERODE MUCH OF THE AREA INVERSIONS...AS ANOTHER FAST
MOVING SYSTEM APPROACHES THE REGION.
FRIDAY THROUGH MONDAY...MEDIUM RANGE MODEL GUIDANCE IS ALL
OVER THE MAP WITH POSSIBLE SOLUTIONS FOR THE REMAINDER OF THE
FORECAST PERIOD. GENERALLY...THE UPPER LEVEL RIDGE WILL BEGIN TO
SHIFT EAST INTRODUCING SOUTHWESTERLY FLOW AND POTENTIALLY BRING
MIXING RELIEF TO FOG SOCKED VALLEY LOCATIONS. A PACIFIC TROUGH
WILL SWING INTO THE NORTHWEST U.S. FRIDAY WITH THE POTENTIAL FOR
SHOWER ACTIVITY TO ENCOMPASS THE REGION. THE GFS IS SHOWING A
SLIGHTLY FASTER PROGRESSION OF THE SYSTEM AND CONCENTRATING
PRECIPITATION CORES IN DIFFERENT LOCATIONS COMPARED TO THE ECWMF.
THE FORECAST WAS ALREADY INDICATING A RETURN OF PRECIPITATION...SO
KEPT THAT GOING. AFTER THE SYSTEM SETTLES INTO THE NORTHERN
ROCKIES SATURDAY...THE GFS KICKS IT EAST WHILE THE ECWMF DIVES IT
SOUTH INTO THE GREAT BASIN. BY THE END OF THE FORECAST PERIOD THE
MODELS ARE OUT OF PHASE...SO TRENDED POPS SLIGHTLY TOWARDS
CLIMATOLOGY AND MADE NO CHANGES TO TEMPERATURES UNTIL A MORE
UNIFIED SOLUTION PRESENTS.
&&
.AVIATION...A PASSING UPPER LEVEL TROUGH WILL MAINTAIN LOW
CEILINGS AND VISIBILITY THROUGH THE OVERNIGHT HOURS...CAUSING THE
HIGHER TERRAIN TO REMAIN OBSCURED. SHOWER ACTIVITY WILL CONTINUE
AREA WIDE THROUGH THE EVENING...BUT WILL BE MAINLY FOCUSED OVER
NORTH CENTRAL IDAHO. SHOWER ACTIVITY IS EXPECTED TO GRADUALLY
DECREASE IN INTENSITY AFTER 23/0600Z ALLOWING FOR AN IMPROVEMENT
IN CEILING AND VISIBILITY.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR
LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...PALLISTER
LONG TERM....ZUMPFE/NOLTE
AVIATION...PALLISTER
000
FXUS65 KTFX 222132
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
232 PM MST SUN NOV 22 2009
.DISCUSSION...
TONIGHT THROUGH TUESDAY...A VIGOROUS UPPER LEVEL TROF CONTINUES TO
TRACK EAST ACROSS THE NORTHERN ROCKIES THIS AFTERNOON AND IS
EXPECTED TO CONTINUE EAST ACROSS THE STATE TONIGHT WITH A RIDGE OF
HIGH PRESSURE BUILDING IN ITS WAKE ON MONDAY. MOIST AND UNSTABLE
WESTERLY FLOW ALOFT WILL SHIFT TO THE NW AS THE TROF AXIS SHIFTS
EAST ACROSS THE REGION TONIGHT. UPPER LEVEL JET DYNAMICS
ASSOCIATED WITH THE TROF WILL TRACK BY TO THE SOUTH OF THE
FORECAST AREA THIS EVENING AND THIS WILL CONTINUE TO KEEP THE BEST
CHANCE FOR SNOW OVER SW MT ZONES THROUGH THIS EVENING. WINTER
WEATHER ADVISORY FOR GALLATIN AND MADISON COUNTIES CONTINUES THROUGH
11PM MST...WHERE BEST LIFT IN ASSOCIATION WITH THE TROUGH WILL
COMBINE WITH MOIST AND UNSTABLE WEST TO NW FLOW ALOFT AND
OROGRAPHIC ENHANCEMENT TO PRODUCE SEVERAL MORE INCHES OF
ADDITIONAL ACCUMULATION THROUGH THIS EVENING. WESTERLY DOWNSLOPE
FLOW WILL LIMIT PRECIPITATION TO ISOLATED SNOW SHOWERS AT BEST FOR
MUCH OF THE NORTH CENTRAL MT PLAINS. SNOW SHOWERS WILL GRADUALLY
DIMINISH AFTER MIDNIGHT AS THE TROF TRACKS EAST OF THE FORECAST
AREA. UPPER LEVEL RIDGE BUILDS IN ON MONDAY FOR DRIER CONDITIONS
WITH TEMPS REMAINING NEAR SEASONAL AVERAGES. THE NEXT DISTURBANCE
IN WESTERLY FLOW TRACKS INTO WESTERN CANADA MONDAY NIGHT AND
ACROSS SOUTHERN ALBERTA ON TUESDAY. THE NORTHERLY TRACK OF THIS
SYSTEM WILL KEEP PRECIPITATION CHANCES MINIMAL...EXCEPT FOR SOME
MTN SNOW SHOWERS. MAIN IMPACT WILL LIKELY BE STRONG WINDS...ESPECIALLY
ALONG THE ROCKY MTN FOR A PERIOD ON TUESDAY AND HIGH WIND
HIGHLIGHTS MAY BECOME NECESSARY. HOENISCH
TUESDAY NIGHT THROUGH SUNDAY NIGHT...BOTH THE ECMWF AND GFS
COMPUTER MODEL RUNS ARE IN GOOD AGREEMENT INTO FRIDAY BUT DIVERGE
WITH THEIR SOLUTIONS THEREAFTER. FOR TUESDAY NIGHT A STRONG UPPER
RIDGE WILL BE APPROACHING THE AREA. THERE COULD BE A FEW SNOW
SHOWERS WITH LINGERING MOISTURE IN THE NORTHWEST FLOW ALOFT. THE
STRONG UPPER RIDGE WILL BE OVER THE AREA WEDNESDAY AND THURSDAY
FOR GENERALLY DRY CONDITIONS WITH TEMPERATURES WELL ABOVE NORMAL
OVER THE PLAINS. RAISED HIGH TEMPERATURES FOR THANKSGIVING 5 TO
10 DEGREES OVER THE PLAINS. IN FACT HIGH TEMPERATURES APPROACHING
RECORD LEVELS ARE NOT OUT OF THE QUESTION. AN UPPER TROUGH IS
FORECAST TO MOVE INTO THE AREA FRIDAY NIGHT AND MODELS HAVE COME
INTO BETTER AGREEMENT ON THE TIMING OF THIS FEATURE. AS THE UPPER
TROUGH MOVES INTO THE AREA EXPECT INCREASING CHANCES OF
PRECIPITATION ALONG WITH COOLER TEMPERATURES. AS WAS MENTIONED
BEFORE MODELS DIFFER LATER IN THE WEEKEND INTO EARLY NEXT WEEK.
INHERITED CHANCES OF PRECIPITATION LOOK REASONABLE AS THEY ARE A
COMPROMISE BETWEEN THE DRIER ECMWF RUN AND THE WETTER GFS RUN.
BLANK
&&
.AVIATION...
UPDATED 1735Z.
UPPER LEVEL LOW PRESSURE TROUGH CENTERED IN EASTERN WASH WILL
CONTINUE TO MOVE EASTWARD AND SPREAD EXTENSIVE CLOUD COVER ACROSS
SOUTHWEST AND CENTRAL MT...ALONG WITH AREAS OF LIGHT SNOW.
CURRENTLY MOST OF THE CLOUDS ARE BETWEEN FL060-FL120 DUE TO VERY DRY
NEAR-SURFACE CONDITIONS...BUT BEGINNING TO SEE SOME LOWER CLOUD
DEVELOPMENT AS MORE MOISTURE MOVES EAST OF THE DIVIDE. EXPECTING
PREDOMINANT VFR CEILINGS THIS AFTN...BUT AIRFIELDS WEST OF A KCTB-TO
KBZN LINE COULD SEE INTERMITTENT MVFR/IFR CONDITIONS ESPECIALLY NEAR
PRECIPITATION AREAS. HIGHER TERRAIN WILL ALSO BE OBSCURED AT
TIMES. WINDS WILL NOT BE AS GUSTY AS PAST FEW DAYS...WITH MAX GUSTS
ONLY 25-30 KTS EXPECTED THIS AFTN. GRADUALLY IMPROVING CONDITIONS
TONIGHT AS THE WEATHER SYSTEM MOVES INTO EASTERN MT. WARANAUSKAS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 43 31 48 / 20 0 10 10
CTB 25 42 30 44 / 10 0 10 10
HLN 22 41 25 44 / 50 10 10 20
BZN 17 36 10 39 / 70 10 0 20
WEY 12 28 7 32 / 90 30 20 20
DLN 16 33 14 38 / 50 10 0 10
HVR 21 47 25 48 / 10 0 10 10
LWT 19 40 24 45 / 40 10 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR MTZ015-
055.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...COULSTON
AVIATION...WARANAUSKAS
WEATHER.GOV/GREATFALLS
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000
FXUS65 KGGW 222131
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
231 PM MST SUN NOV 22 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH TUESDAY...
AN UPPER LEVEL CYCLONE IS SPINNING EASTWARD OVER EASTERN
WASHINGTON THIS AFTERNOON. AN EARLIER BAND OF SNOW OVER WESTERN
MONTANA HAS FALLEN APART AFTER MOVING EAST OF THE ROCKIES WITH A
LACK OF UPPER SUPPORT. THE STRONGEST UPPER JET SUPPORT WITH THIS
SYSTEM IS OVER SOUTHEAST IDAHO AND IT WILL REMAIN WELL SOUTH OF
NORTHEAST MONTANA. THE UPPER LOW CENTER WILL DRIFT ACROSS
SOUTHEAST MONTANA OVERNIGHT AND IT MAY PRODUCE A FEW AREAS OF VERY
LIGHT SNOW ACROSS THE SOUTHERN ZONES TONIGHT AND EARLY
MONDAY...BUT MEASURABLE PRECIPITATION IS HIGHLY UNLIKELY.
THE UPPER LOW WILL DROP INTO THE CENTRAL PLAINS MONDAY WITH DRIER
AIR ALOFT MOVING OVER THE FORECAST AREA AS UPPER RIDGING BUILDS
IN FROM THE PACIFIC NORTHWEST. THE SKY SHOULD CLEAR FROM WEST TO
EAST DURING THE AFTERNOON WITH A CLEAR SKY OVER THE ENTIRE AREA BY
MONDAY NIGHT. AFTERNOON MAXIMUM TEMPERATURES WILL REMAIN ABOVE
SEASONAL AVERAGES. WARM ADVECTION WILL COMMENCE MONDAY NIGHT
CREATING RATHER LARGE MINIMUM TEMPERATURE DIFFERENCES BETWEEN THE
HIGHER ELEVATIONS AND THE TYPICAL COLD AIR DRAINAGE LOCATIONS.
A VIGOROUS SHORTWAVE TROUGH WILL DIG SOUTHEAST OVER THE CANADIAN
PRAIRIES TUESDAY DRIVING A STRONG COLD FRONT THROUGH NORTHEAST
MONTANA. A STRONG NORTHWEST WIND WILL DEVELOP ALONG AND BEHIND THE
COLD FRONT. 850MB WIND SPEEDS REACH UPWARDS OF 30KT AND COLD AIR
ADVECTION AND A STRONG PRESSURE GRADIENT SHOULD CARRY A RATHER
STRONG AND GUSTY SURFACE WIND. AJZ
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
MAIN FORECAST IMPACT IN THE EXTENDED WILL BE STRONG UPPER RIDGE WED
INTO THANKSGIVING AND COLD TROUGH LATE FRIDAY INTO MONDAY. MODEL TRENDS
ON WED AND THU ARE CONSISTENT WITH HIGH AMPLITUDE UPPER RIDGE BUILDING
OVER INTER MOUNTAIN WEST BETWEEN TROUGH OVER ERN US AND DIGGING
SHORTWAVE ENERGY ALONG PAC COAST. ECMWF LITTLE FLATTER THAN GFS BUT
HEIGHTS NEAR 570DM WITH 850MB TEMPS NEAR +10C WILL KEEP MAX TEMPS
WELL ABOVE NORMALS INTO THE 50S. DID INCREASE TEMPS A LITTLE AND
DECREASE SKY COVER WITH THE RIDGE AXIS OVER CNTRL MT. THE GFS AND
ECMWF DO BEGIN TO DIVERGE ON FRIDAY NIGHT AS ECMWF IS A LITTLE
SLOWER AND DIGS MAIN SHORTWAVE TROUGH ENERGY FARTHER SOUTH. THE
GFS ENSEMBLES AGREE ON THE TROUGH BUT TIMING AFTER SATURDAY
REMAINS UNCERTAIN. ONLY MINOR CHANGES MADE TO TEMPS...POPS AND SKY
COVER. SLA
SATURDAY THROUGH SUNDAY NIGHT...THE LAST PART OF THE FORECAST
PERIOD BEGINS ON SATURDAY WITH MAJOR SHORTWAVE TROUGH DIVING SOUTH
OUT OF CANADA IN A MERIDIONAL PATTERN. BOTH THE GFS AND THE EC HAVE
THIS SET UP BUT THE GFS HAS MORE AMPLITUDE TO THE PATTERN AND HAS
ALSO BEEN MORE CONSISTENT THAN THE EC. THE MODELS HINT AT A SURGE OF
ARCTIC AIR SOUTH FROM ALASKA SATURDAY NIGHT. THE MODELS HAVE HINTED
AT THE ON SET OF A COLDER AIR MASS IN PREVIOUS RUNS...HOWEVER...LOW
CONFIDENCE MUST BE EXHIBITED NOW DUE TO THE FACT THAT THE MODELS ARE
VARYING ON INTENSITY AND TIMING OF THE COLD SURGE. THE ONLY TWEAKS
THAT WERE MADE WERE TO TEMPERATURE TO DROP DOWN A DEGREE IN
ACCORDANCE WITH A COOLER PATTERN. SHALLENBERGER
&&
.AVIATION...
VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT AN INTO TOMORROW. MID
LEVEL CEILINGS AT 20KFT WILL DROP TO 10KFT BY TOMORROW MORNING.
WINDS WILL BE LIGHT OUT OF THE EAST TONIGHT AT 10 KTS BEFORE
SHIFTING TO NORTHWEST AT 1O TO 15 KNOTS BY LATE MORNING. A FEW
FLURRIES CAN BE EXPECTED IN THE SOUTHERN ZONES TONIGHT AS WELL.
SHALLENBERGER
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 221748
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1035 AM MST SUN NOV 22 2009
AVIATION SECTION UPDATED...
.UPDATE..
SATELLITE IMAGERY THIS MORNING SHOWS A WELL DEVELOPED CYCLONE
MOVING INTO THE PACIFIC NW WITH RADAR IMAGERY SHOWING A SHIELD OF
PRECIPITATION IN ADVANCE OF THIS FEATURE ALREADY MOVING INTO
WESTERN/SW/CENTRAL MT. DRY AIR IN LOWER LEVELS IS INHIBITING
PRECIPITATION FROM REACHING THE GROUND ALONG THE EASTERN PORTION OF
THE PRECIP SHIELD HOWEVER OBSERVATIONS OVER WESTERN MT AND WEB CAMS
ALONG THE CONTINENTAL DIVIDE INDICATE SNOW IS BEGINNING TO REACH THE
SURFACE FROM AREAS ALONG THE CONTINENTAL DIVIDE WESTWARD WHERE LOW
LEVELS HAVE BEEN SUFFICIENTLY MOISTENED. HAVE RAISED POPS SOME OVER
WESTERN AND SW ZONES...ESPECIALLY IN THE MTNS WHERE ALL INDICATIONS
POINT TO PRECIP ALREADY OCCURRING AND HAVE LOWERED OR REMOVED POPS
FROM EASTERN AND NORTH CENTRAL AREAS THROUGH THE REMAINDER OF THIS
MORNING. SYSTEM MOVES THROUGH THIS AFTERNOON AND EVENING WITH SW MT
AND THE WESTERN MTNS STILL LOOKING TO SEE THE BRUNT OF THE
PRECIPITATION WITH JUST SOME FLURRIES OR LIGHT SNOW SHOWERS POSSIBLE
OVER THE REMAINDER OF THE AREA. BULK OF THE ENERGY WITH THE INCOMING
SYSTEM WILL DIVE SOUTHEAST THROUGH ID/WY THIS EVENING...WITH THE MTN
RANGES OF GALLATIN AND MADISON COUNTIES LIKELY SEEING THE HIGHEST
SNOW AMOUNTS WITH 1 TO 3 INCHES IN THE LOWER
VALLEYS(BOZEMAN/ENNIS)...3 TO 5 INCHES IN THE HIGHER VALLEYS(W
YELLOWSTONE)...AND 5 TO 9 INCHES IN THE MTNS ABOVE 7000 FT. HOENISCH
&&
.AVIATION...
UPDATED 1735Z.
UPPER LEVEL LOW PRESSURE TROUGH CENTERED IN EASTERN WASH WILL
CONTINUE TO MOVE EASTWARD AND SPREAD EXTENSIVE CLOUD COVER ACROSS
SOUTHWEST AND CENTRAL MT...ALONG WITH AREAS OF LIGHT SNOW.
CURRENTLY MOST OF THE CLOUDS ARE BETWEEN FL060-FL120 DUE TO VERY DRY
NEAR-SURFACE CONDITIONS...BUT BEGINNING TO SEE SOME LOWER CLOUD
DEVELOPMENT AS MORE MOISTURE MOVES EAST OF THE DIVIDE. EXPECTING
PREDOMINANT VFR CEILINGS THIS AFTN...BUT AIRFIELDS WEST OF A KCTB-TO
KBZN LINE COULD SEE INTERMITTENT MVFR/IFR CONDITIONS ESPECIALLY NEAR
PRECIPITATION AREAS. HIGHER TERRAIN WILL ALSO BE OBSCURED AT
TIMES. WINDS WILL NOT BE AS GUSTY AS PAST FEW DAYS...WITH MAX GUSTS
ONLY 25-30 KTS EXPECTED THIS AFTN. GRADUALLY IMPROVING CONDITIONS
TONIGHT AS THE WEATHER SYSTEM MOVES INTO EASTERN MT. WARANAUSKAS
&&
.PREV DISCUSSION...
/ISSUED 517 AM MST SUN NOV 22 2009/
TODAY THROUGH TUESDAY...A MOIST PACIFIC WEATHER SYSTEM CURRENTLY
OVER THE PACIFIC NORTHWEST WILL MOVE EAST INTO THE NORTHERN
ROCKIES TODAY. SNOW SHOWERS WILL BEGIN IN THE MOUNTAINS OF
WESTERN MONTANA LATER THIS MORNING...THEN THEY WILL SPREAD INTO
THE MOUNTAINS OF SOUTHWEST AND CENTRAL MONTANA FOR THIS AFTERNOON
AND EVENING. THE SYSTEM WILL WEAKEN AND BEGIN TO SPLIT AS IT MOVES
INTO THE AREA...WHICH WILL MOVE THE BEST CHANCE FOR ACCUMULATING
SNOW AT LOWER ELEVATIONS INTO SOUTHWEST MONTANA. THE STRONGEST
OROGRAPHIC LIFT WILL BE IN THE MOUNTAIN AREAS OF MADISON AND
GALLATIN COUNTIES. HAVE THEREFORE GONE WITH A WINTER WEATHER
ADVISORY FOR SNOW THERE...AS 2 TO 4 INCHES OF SNOWFALL ARE
POSSIBLE IN THE VALLEYS WITH 5 TO 9 INCHES EXPECTED IN THE
MOUNTAINS. BREEZY SOUTHERLY WINDS THIS AFTERNOON WILL SHIFT MORE
WESTERLY THIS EVENING...CAUSING AREAS OF BLOWING SNOW THROUGH
FAVORED VALLEYS. LESSER AMOUNTS ARE EXPECTED ACROSS THE REMAINDER
OF SOUTHWEST MONTANA. ACCUMULATING SNOW WILL ALSO OCCUR IN THE
MOUNTAINS OF THE ROCKY MOUNTAIN FRONT...BUT IT SHOULD BE LIMITED
TO AREAS ABOVE 5000 FEET DUE TO INCREASING WESTERLY DOWNSLOPE
WINDS. DOWNSLOPE WINDS WILL ALSO LIMIT RAIN AND SNOW SHOWERS OVER
THE PLAINS. LINGERING SNOW SHOWERS WILL DECREASE OVERNIGHT AS THE
SYSTEM EXITS THE AREA. AN UPPER LEVEL HIGH PRESSURE RIDGE WILL
BUILD INTO THE AREA FOR MONDAY THROUGH TUESDAY. A WEAK
DISTURBANCE WILL MOVE THROUGH THE RIDGE MONDAY AND BRING A CHANCE
OF SNOW SHOWERS TO THE MOUNTAINS. A STRONGER SHORTWAVE TROUGH WILL
THEN FLATTEN THE RIDGE MONDAY NIGHT INTO TUESDAY. THIS WILL BRING
A CHANCE OF SNOW SHOWERS TO THE MOUNTAINS ONCE AGAIN...BUT IT WILL
ALSO BRING STRONG WESTERLY DOWNSLOPE WINDS TO THE PLAINS. THIS MAY
REQUIRE HIGH WIND HIGHLIGHTS...BUT WILL CONTINUE TO MONITOR THE
SITUATION. NEAR NORMAL TEMPERATURES TODAY WILL WARM TO AROUND 10
DEGREES ABOVE NORMAL BY TUESDAY. COULSTON
TUESDAY NIGHT THROUGH SUNDAY NIGHT...BOTH THE ECMWF AND GFS
COMPUTER MODEL RUNS ARE IN GOOD AGREEMENT INTO FRIDAY BUT DIVERGE
WITH THEIR SOLUTIONS THEREAFTER. FOR TUESDAY NIGHT A STRONG UPPER
RIDGE WILL BE APPROACHING THE AREA. THERE COULD BE A FEW SNOW
SHOWERS WITH LINGERING MOISTURE IN THE NORTHWEST FLOW ALOFT. THE
STRONG UPPER RIDGE WILL BE OVER THE AREA WEDNESDAY AND THURSDAY
FOR GENERALLY DRY CONDITIONS WITH TEMPERATURES WELL ABOVE NORMAL
OVER THE PLAINS. RAISED HIGH TEMPERATURES FOR THANKSGIVING 5 TO
10 DEGREES OVER THE PLAINS. IN FACT HIGH TEMPERATURES APPROACHING
RECORD LEVELS ARE NOT OUT OF THE QUESTION. AN UPPER TROUGH IS
FORECAST TO MOVE INTO THE AREA FRIDAY NIGHT AND MODELS HAVE COME
INTO BETTER AGREEMENT ON THE TIMING OF THIS FEATURE. AS THE UPPER
TROUGH MOVES INTO THE AREA EXPECT INCREASING CHANCES OF
PRECIPITATION ALONG WITH COOLER TEMPERATURES. AS WAS MENTIONED
BEFORE MODELS DIFFER LATER IN THE WEEKEND INTO EARLY NEXT WEEK.
INHERITED CHANCES OF PRECIPITATION LOOK REASONABLE AS THEY ARE A
COMPROMISE BETWEEN THE DRIER ECMWF RUN AND THE WETTER GFS RUN.
BLANK
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 40 28 44 31 / 20 20 10 10
CTB 39 26 43 30 / 20 20 10 10
HLN 40 24 42 24 / 50 30 10 10
BZN 35 16 34 12 / 100 60 10 20
WEY 28 12 27 10 / 100 80 30 30
DLN 33 14 30 13 / 90 40 10 10
HVR 44 24 45 26 / 10 20 10 10
LWT 38 23 38 25 / 40 40 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR MTZ015-
055.
&&
$$
SHORT TERM...COULSTON
LONG TERM...BLANK
AVIATION...BLANK
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 221655
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
955 AM MST SUN NOV 22 2009
.SHORT TERM...VALID FOR TDY AND MON...
SHORTWAVE MOVING THROUGH THE PACIFIC NORTHWEST INTO WESTERN
MONTANA SEEMS TO BE PRODUCING DECENT SNOW SHOWERS. SYSTEM IS
FAVORING A BIT MORE NORTHERLY TRACK THAN PREVIOUS RUNS AND IS
PREPARED TO BRING A BIT MORE DYNAMICS TO THE WESTERN ZONES LATE
THIS AFTERNOON AND EVENING. ALONG WITH THE FAVORABLE UPPER
FLOW...SOUNDINGS SHOW SOME LOW LEVEL INSTABILITY AND THINK THAT
INTENSE SNOW SHOWERS ARE LIKELY LATER THIS AFTERNOON. ISSUING AN
ADVISORY FOR THE NON MOUNTAIN ZONES OF PARK COUNTY THINKING THAT A
QUICK 2 TO 3 INCHES COULD FALL AROUND SUNSET. ELSEWHERE...PULLED
POPS A BIT FURTHER DOWN ACROSS THE CENTRAL ZONES THIS AFTERNOON AS
THE SYSTEM IS NOT QUIET SPREADING MOISTURE AS FAR EAST AS QUICKLY
AS PREVIOUSLY INDICATED. BORSUM
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
THE EXTENDED PERIOD BEGINS TUESDAY MORNING WITH GENERALLY FAIR
AGREEMENT BETWEEN THE GFS AND ECMWF. THE EVOLUTION OF THE GFS
LATE IN THE EXTENDED PERIOD APPEARS SUSPECT. THEREFORE...TRENDED
INHERITED FORECASTS TOWARD THE ECMWF. AN UPPER-LEVEL TROUGH
PASSES EAST OF THE CWA LATE TUESDAY INTO EARLY WEDNESDAY.
ADJUSTED POPS TO COVER MAINLY EASTERN ZONES AND THE HIGHER
TERRAIN DURING THIS TIME. AN UPPER-LEVEL RIDGE BUILDS OVER THE
WESTERN CONUS THROUGH THE REMAINDER OF THE WORK WEEK. LIMITED
POPS AND WARMED TEMPERATURE FORECASTS SLIGHTLY THROUGH FRIDAY IN
RESPONSE. THE NEXT UPPER-TROUGH PASSES THROUGH THE REGION LATE
FRIDAY THROUGH EARLY SUNDAY. MADE MINOR ADJUSTMENTS TO POPS AND
TEMPERATURE FORECASTS DURING THIS TIME. SCHUKNECHT
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL ACROSS THE AREA THIS MORNING. CLOUDS
WILL INCREASE FROM WEST TO EAST THROUGH THE DAY AND TONIGHT AS A
STORM SYSTEM MOVES INTO THE AREA. SNOW WILL ALSO INCREASE FROM
WEST TO EAST THROUGH TONIGHT. EXPECT MOUNTAIN OBSCURATIONS AND
MVFR CONDITIONS AS THE SNOW MOVES ACROSS. LOCALIZED IFR
CONDITIONS WILL ALSO BE POSSIBLE. GUSTY WINDS WILL ALSO CONTINUE
ALONG THE BEARTOOTH FOOTHILLS WEST INTO KLVM. EXPECT SUSTAINED
WINDS AROUND 25 KTS WITH GUSTS UP TO 40 KTS THROUGH THIS
AFTERNOON FOR THESE LOCATIONS. SOLUM
&&
.PRELIMINARY POINT TEMP/POPS...
TDY MON TUE WED THU FRI SAT
-------------------------------------------------------
BIL 042 026/040 025/047 030/047 031/055 033/055 033/046
2/W 41/B 00/B 10/B 00/U 01/B 22/W
LVM 036 017/034 016/042 023/048 027/054 028/050 026/041
8/J 82/J 01/N 10/B 00/N 02/W 32/W
HDN 045 025/043 022/049 028/048 028/056 030/056 030/049
1/B 42/J 00/B 10/B 00/U 01/B 22/W
MLS 046 026/043 023/048 025/044 025/053 030/055 032/047
0/U 32/J 00/B 20/B 00/U 01/B 22/W
4BQ 045 025/040 022/046 025/043 024/052 029/055 030/047
0/B 42/W 01/B 20/B 00/U 01/U 22/W
BHK 044 023/040 022/044 024/040 021/051 027/052 029/046
0/U 22/W 01/B 20/B 00/U 01/B 22/W
SHR 044 024/038 017/047 025/046 024/054 027/055 025/046
1/B 42/J 00/B 21/B 10/U 01/B 22/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT FROM 3 PM THIS AFTERNOON TO
MIDNIGHT MST TONIGHT FOR ZONES 40-64-65.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 221645 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
945 AM MST SUN NOV 22 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...
A RATHER DYNAMIC STORM SYSTEM IS PASSING OVER THE PACIFIC
NORTHWEST THIS MORNING. AN AREA OF WARM AIR ADVECTION AHEAD OF
THIS SYSTEM IS TRIGGERING A BAND OF SNOW OVER WESTERN MONTANA.
THIS AREA OF MOISTURE WILL CONTINUE TO PUSH EAST TODAY...BUT IT
WILL ENCOUNTER A VERY DRY AIRMASS BELOW 600MB...WHICH WILL RENDER
THE INCOMING MOISTURE TO ONLY INCREASING CLOUD COVER AT OR ABOVE
12K FT OVER THE LOCAL AREA. THEREFORE...WEATHER MENTION WAS
REMOVED FROM THE SOUTHWEST ZONES THIS AFTERNOON. STRONGER LIFT
WILL ARRIVE TONIGHT...BUT ONLY A PERIOD LIGHT SNOW OR FLURRIES
IS EXPECTED ACROSS THE SOUTHERN ZONES DUE TO LIMITED MOISTURE.
TEMPERATURES WILL BE COOLER TODAY...BUT STILL REMAIN ABOVE
SEASONAL AVERAGES...ALONG WITH MUCH LESS WIND THAN YESTERDAY. THE
OVERALL FORECAST REMAINS IN GOOD SHAPE WITH THE ONLY CHANGE THE
AFOREMENTIONED REMOVAL OF WEATHER THIS AFTERNOON. AJZ
PREVIOUS SHORT TERM DISCUSSION...
A NARROW RIDGE MOVING OVER EASTERN MONTANA WILL START THE DAY OFF
WITH SUNSHINE AND MUCH QUIETER SOUTHERLY WINDS. THE RIDGE WILL BE
PUSHED ASIDE BY THE NEXT UPPER TROUGH THAT CAN BE SEEN ON THE GOES
WATER VAPOR IMAGERY SLAMMING INTO THE NORTHWEST COAST. AN
ASSOCIATED WEAK WARM FRONT WILL BEGIN TO INCREASE CLOUD COVER FROM
THE WEST THIS AFTERNOON. MOISTURE WILL MAKE OVER THE DIVIDE AND
INTO CENTRAL MONTANA BY LATE AFTERNOON. LEFT SLIGHT CHANCE POPS IN
THE FAR WESTERN ZONES FOR RAIN AND SNOW BUT EXPECT VERY LITTLE TO
HIT THE GROUND.
TONIGHT...THE UPPER TROUGH DIVES SOUTHEAST INTO NORTHERN COLORADO
BY LATE TONIGHT TAKING MOST ENERGY TO OUR SOUTH. A VORT MAX
CENTERED OVER SOUTHEASTERN MONTANA COULD SPREAD LIGHT SNOW SHOWER
ACTIVITY NORTH INTO OUR SOUTHERN ZONES BUT NOT MUCH ACCUMULATION
IS EXPECTED SINCE THE LOWER ATMOSPHERE REMAINS DRY. WILL GO WITH
SLIGHT CHANCE POPS. CLOUD COVER WILL PREVENT OVERNIGHT
TEMPERATURES FROM PLUNGING TOO LOW.
MONDAY...GENERAL TROUGHINESS WILL MAINTAIN COOL CONDITIONS AND
CLOUD COVER. HOWEVER HIGHS WILL STILL BE SLIGHTLY ABOVE AVERAGE
FOR THIS TIME OF YEAR. NOT MUCH IN THE WAY OF PRECIPITATION IS
EXPECTED EITHER. BUT WILL KEEP SLIGHT CHANCE POPS IN SOUTHERN
ZONES AS A WEAK FRONT AND DYNAMICS GENERATE SOME SHOWERS JUST
SOUTH OF OUR SOUTHERN CWA BORDER.
MONDAY NIGHT...AN UPPER RIDGE THEN LEANS OVER OUR AREA TO BRING
WAA AND CLEARING SKIES. OVERNIGHT LOWS WILL DROP A LITTLE LOWER
WITH RADIATIONAL COOLING. BUT WARM AIR ALOFT WILL SURGE IN FROM
THE WEST...MODERATING THE LOWS.
TUESDAY...LATE AFTERNOON A COMPACT CYCLONE WILL DEVELOP NEAR THE
BORDER BETWEEN SASKATCHEWAN AND MANITOBA. THIS STORM WILL SEND A
DRY COLD FRONT SOUTH INTO OUR AREA. THIS WILL VEER WINDS AROUND TO
THE NORTHWEST BUT MIGHT BE TOO LATE IN THE DAY TO BRING ANY REAL
STRONG WINDS TO THE AREA. SCT
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
MODELS SHOW GOOD AGREEMENT UNTIL A COLD FRONT MOVES THROUGH THE
AREA FRIDAY NIGHT. A SHORTWAVE TROUGH WILL DIVE SOUTHEAST THROUGH
THE DAKOTAS TUESDAY NIGHT AND WEDNESDAY BRINGING SOMEWHAT COOLER
AIR MAINLY TO THE EASTERN ZONES FOR WEDNESDAY. IT LOOKS LIKE THE
PRECIPITATION WITH THIS SYSTEM WILL STAY TO THE EAST.
UPPER RIDGE BUILDS INTO MONTANA FOR THANKSGIVING DAY GIVING THE
FORECAST AREA A WARM AND DRY DAY. THE WARM TEMPERATURES WILL
LINGER THROUGH FRIDAY AS THE RIDGE MOVES EAST.
A COLD FRONT WILL PASS THROUGH EASTERN MONTANA FRIDAY NIGHT WITH
AN UPPER TROUGH ON SATURDAY. ENOUGH MOISTURE CURRENTLY FORECASTED
WITH THIS SYSTEM TO WARRANT A SLIGHT CHANCE OF RAIN AND SNOW.
WHILE THE ECMWF MOVES THE TROUGH TO THE EAST NEXT SUNDAY AND
BRINGS ANOTHER UPPER RIDGE WITH WARMER TEMPERATURES INTO THE
STATE... THE GFS LINGERS THE TROUGH OVER THE AREA AND HAS MUCH
COLDER AIR DROPPING IN FROM CANADA. GIVEN THE WARM PATTERN OF
LATE...WILL SIDE TOWARDS THE WARMER ECMWF FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. WILL SEE CLEAR SKIES THIS MORNING WITH LIGHT
MAINLY SOUTHEAST WINDS. MID AND HIGH CLOUDS WILL MOVE IN FROM THE
WEST THIS AFTERNOON AND BECOME A BROKEN TO OVERCAST MID LEVEL DECK
BY THIS EVENING. MAY SEE A FEW FLURRIES TONIGHT AS A COLD FRONT
TURNS WINDS TO THE NORTHWEST AT 5 TO 10 KNOTS. FORRESTER
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 221643
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
943 AM MST SUN NOV 22 2009
.UPDATE..
SATELLITE IMAGERY THIS MORNING SHOWS A WELL DEVELOPED CYCLONE
MOVING INTO THE PACIFIC NW WITH RADAR IMAGERY SHOWING A SHIELD OF
PRECIPITATION IN ADVANCE OF THIS FEATURE ALREADY MOVING INTO
WESTERN/SW/CENTRAL MT. DRY AIR IN LOWER LEVELS IS INHIBITING PRECIPITATION
FROM REACHING THE GROUND ALONG THE EASTERN PORTION OF THE PRECIP
SHIELD HOWEVER OBSERVATIONS OVER WESTERN MT AND WEB CAMS ALONG THE
CONTINENTAL DIVIDE INDICATE SNOW IS BEGINNING TO REACH THE SURFACE
FROM AREAS ALONG THE CONTINENTAL DIVIDE WESTWARD WHERE LOW LEVELS
HAVE BEEN SUFFICIENTLY MOISTENED. HAVE RAISED POPS SOME OVER
WESTERN AND SW ZONES...ESPECIALLY IN THE MTNS WHERE ALL
INDICATIONS POINT TO PRECIP ALREADY OCCURRING AND HAVE LOWERED OR
REMOVED POPS FROM EASTERN AND NORTH CENTRAL AREAS THROUGH THE
REMAINDER OF THIS MORNING. SYSTEM MOVES THROUGH THIS AFTERNOON AND
EVENING WITH SW MT AND THE WESTERN MTNS STILL LOOKING TO SEE THE
BRUNT OF THE PRECIPITATION WITH JUST SOME FLURRIES OR LIGHT SNOW
SHOWERS POSSIBLE OVER THE REMAINDER OF THE AREA. BULK OF THE
ENERGY WITH THE INCOMING SYSTEM WILL DIVE SOUTHEAST THROUGH ID/WY
THIS EVENING...WITH THE MTN RANGES OF GALLATIN AND MADISON
COUNTIES LIKELY SEEING THE HIGHEST SNOW AMOUNTS WITH 1 TO 3
INCHES IN THE LOWER VALLEYS(BOZEMAN/ENNIS)...3 TO 5 INCHES IN THE
HIGHER VALLEYS(W YELLOWSTONE)...AND 5 TO 9 INCHES IN THE MTNS ABOVE
7000 FT. HOENISCH
&&
.AVIATION...
UPDATED 1155Z.
ANOTHER PACIFIC WEATHER SYSTEM WILL MOVE THROUGH THE FORECAST
AREA OVERNIGHT. IN ADVANCE OF THIS WEATHER SYSTEM MOISTURE WILL
BE INCREASING FROM THE WEST TODAY. SNOW SHOULD REACH THE WESTERN
MOUNTAINS AROUND MID-MORNING THEN SPREAD OVER SOUTHWEST MONTANA
FROM THEN THROUGH EARLY AFTERNOON. EXPECT MOUNTAINS TO BE TOTALLY
OBSCURED AT TIMES. VALLEYS IN SOUTHWEST MONTANA WILL SEE A PERIOD
OF MVFR/IFR CONDITIONS IN THE SNOW. THE PLAINS WILL SEE
ISOLATED/SCATTERED SNOW SHOWERS THIS AFTERNOON THROUGH THIS
EVENING BUT CONDITIONS ARE EXPECTED TO BE VFR WITH THE EXCEPTION
OF POSSIBLE MVFR CONDITIONS NEAR KLWT. WOULD NOT BE SURPRISED IF
SOUTHWEST TO WEST WINDS ARE A LITTLE STRONGER THAN FORECAST THIS
AFTERNOON INTO TONIGHT. DO NOT HAVE REAL GOOD CONFIDENCE ON THE
TIMING OF THE SNOW FOR THE KBZN TAF. SOME GUIDANCE SUGGESTS SNOW
WILL BE DURING THE 18Z-00Z TIME FRAME WHILE OTHER GUIDANCE
SUGGESTS SNOW WILL BE MORE IN THE 21Z-03Z TIME FRAME. BLANK
&&
.PREV DISCUSSION...
/ISSUED 517 AM MST SUN NOV 22 2009/
TODAY THROUGH TUESDAY...A MOIST PACIFIC WEATHER SYSTEM CURRENTLY
OVER THE PACIFIC NORTHWEST WILL MOVE EAST INTO THE NORTHERN
ROCKIES TODAY. SNOW SHOWERS WILL BEGIN IN THE MOUNTAINS OF
WESTERN MONTANA LATER THIS MORNING...THEN THEY WILL SPREAD INTO
THE MOUNTAINS OF SOUTHWEST AND CENTRAL MONTANA FOR THIS AFTERNOON
AND EVENING. THE SYSTEM WILL WEAKEN AND BEGIN TO SPLIT AS IT MOVES
INTO THE AREA...WHICH WILL MOVE THE BEST CHANCE FOR ACCUMULATING
SNOW AT LOWER ELEVATIONS INTO SOUTHWEST MONTANA. THE STRONGEST
OROGRAPHIC LIFT WILL BE IN THE MOUNTAIN AREAS OF MADISON AND
GALLATIN COUNTIES. HAVE THEREFORE GONE WITH A WINTER WEATHER
ADVISORY FOR SNOW THERE...AS 2 TO 4 INCHES OF SNOWFALL ARE
POSSIBLE IN THE VALLEYS WITH 5 TO 9 INCHES EXPECTED IN THE
MOUNTAINS. BREEZY SOUTHERLY WINDS THIS AFTERNOON WILL SHIFT MORE
WESTERLY THIS EVENING...CAUSING AREAS OF BLOWING SNOW THROUGH
FAVORED VALLEYS. LESSER AMOUNTS ARE EXPECTED ACROSS THE REMAINDER
OF SOUTHWEST MONTANA. ACCUMULATING SNOW WILL ALSO OCCUR IN THE
MOUNTAINS OF THE ROCKY MOUNTAIN FRONT...BUT IT SHOULD BE LIMITED
TO AREAS ABOVE 5000 FEET DUE TO INCREASING WESTERLY DOWNSLOPE
WINDS. DOWNSLOPE WINDS WILL ALSO LIMIT RAIN AND SNOW SHOWERS OVER
THE PLAINS. LINGERING SNOW SHOWERS WILL DECREASE OVERNIGHT AS THE
SYSTEM EXITS THE AREA. AN UPPER LEVEL HIGH PRESSURE RIDGE WILL
BUILD INTO THE AREA FOR MONDAY THROUGH TUESDAY. A WEAK
DISTURBANCE WILL MOVE THROUGH THE RIDGE MONDAY AND BRING A CHANCE
OF SNOW SHOWERS TO THE MOUNTAINS. A STRONGER SHORTWAVE TROUGH WILL
THEN FLATTEN THE RIDGE MONDAY NIGHT INTO TUESDAY. THIS WILL BRING
A CHANCE OF SNOW SHOWERS TO THE MOUNTAINS ONCE AGAIN...BUT IT WILL
ALSO BRING STRONG WESTERLY DOWNSLOPE WINDS TO THE PLAINS. THIS MAY
REQUIRE HIGH WIND HIGHLIGHTS...BUT WILL CONTINUE TO MONITOR THE
SITUATION. NEAR NORMAL TEMPERATURES TODAY WILL WARM TO AROUND 10
DEGREES ABOVE NORMAL BY TUESDAY. COULSTON
TUESDAY NIGHT THROUGH SUNDAY NIGHT...BOTH THE ECMWF AND GFS
COMPUTER MODEL RUNS ARE IN GOOD AGREEMENT INTO FRIDAY BUT DIVERGE
WITH THEIR SOLUTIONS THEREAFTER. FOR TUESDAY NIGHT A STRONG UPPER
RIDGE WILL BE APPROACHING THE AREA. THERE COULD BE A FEW SNOW
SHOWERS WITH LINGERING MOISTURE IN THE NORTHWEST FLOW ALOFT. THE
STRONG UPPER RIDGE WILL BE OVER THE AREA WEDNESDAY AND THURSDAY
FOR GENERALLY DRY CONDITIONS WITH TEMPERATURES WELL ABOVE NORMAL
OVER THE PLAINS. RAISED HIGH TEMPERATURES FOR THANKSGIVING 5 TO
10 DEGREES OVER THE PLAINS. IN FACT HIGH TEMPERATURES APPROACHING
RECORD LEVELS ARE NOT OUT OF THE QUESTION. AN UPPER TROUGH IS
FORECAST TO MOVE INTO THE AREA FRIDAY NIGHT AND MODELS HAVE COME
INTO BETTER AGREEMENT ON THE TIMING OF THIS FEATURE. AS THE UPPER
TROUGH MOVES INTO THE AREA EXPECT INCREASING CHANCES OF
PRECIPITATION ALONG WITH COOLER TEMPERATURES. AS WAS MENTIONED
BEFORE MODELS DIFFER LATER IN THE WEEKEND INTO EARLY NEXT WEEK.
INHERITED CHANCES OF PRECIPITATION LOOK REASONABLE AS THEY ARE A
COMPROMISE BETWEEN THE DRIER ECMWF RUN AND THE WETTER GFS RUN.
BLANK
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 40 28 44 31 / 20 20 10 10
CTB 39 26 43 30 / 20 20 10 10
HLN 40 24 42 24 / 50 30 10 10
BZN 35 16 34 12 / 100 60 10 20
WEY 28 12 27 10 / 100 80 30 30
DLN 33 14 30 13 / 90 40 10 10
HVR 44 24 45 26 / 10 20 10 10
LWT 38 23 38 25 / 40 40 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR MTZ015-
055.
&&
$$
SHORT TERM...COULSTON
LONG TERM...BLANK
AVIATION...BLANK
WEATHER.GOV/GREATFALLS
000
FXUS65 KMSO 221558 AAA
AFDMSO
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MISSOULA MT
858 AM MST SUN NOV 22 2009
.DISCUSSION...DID AN UPDATE TO INCREASE CHANCE OF SNOW ACROSS THE
MISSOULA/BITTERROOT VALLEYS THIS MORNING. THE LOW LEVELS OF THE
ATMOSPHERE HAVE MOISTENED ENOUGH TO ALLOW PRECIPITATION TO FALL
EARLIER THAN PREVIOUSLY EXPECTED. LOCATIONS DOWN THE
MISSOULA/BITTERROOT VALLEY CAN EXPECT UP TO AN INCH OF SNOW
ACCUMULATION BY THIS AFTERNOON...LOCALLY UP TO 3 INCHES OVER THE
HIGHER BENCHES SURROUNDING THE VALLEY FLOOR. OTHERWISE FORECAST
LOOKS ON TRACK WITH SNOWY FORECAST...ESPECIALLY OVER THE HIGHER
TERRAIN OF NORTH CENTRAL IDAHO. WINTER WEATHER ADVISORIES REMAIN
IN PLACE...PLEASE SEE WWW.WEATHER.GOV/MISSOULA FOR FURTHER DETAILS.
&&
.AVIATION...ANOTHER ACTIVE WEATHER DAY IS EXPECTED WITH AN UPPER
TROUGH AND COLD FRONTAL PASSAGE. THE FRONT WILL MOVE THROUGH
NORTHERN IDAHO BY 22/1800Z THEN THROUGH WESTERN MONTANA BY
22/2200Z. WIDESPREAD SNOW SHOWERS WILL RESULT...SOME HEAVY AT
TIMES. INCREASED WEST WINDS WILL ALSO BE OF CONCERN AS BLOWING
SNOW MAY LIMIT VISIBILITY. LOW CEILINGS WILL OBSCURE HIGHER
TERRAIN ACROSS THE ENTIRE REGION. ACCUMULATING SNOW BETWEEN 1 TO 2
INCHES IS POSSIBLE ON KMSO AND KGPI RUNWAYS BETWEEN 22/1800Z AND 22/2100Z.
SHOWERS WILL BEGIN TO DECREASE BY LATE AFTERNOON...BUT LINGER WELL
INTO THE EVENING MAINLY OVER NORTHERN IDAHO AND THE BITTERROOT
MOUNTAINS.
&&
.PREV DISCUSSION... /ISSUED 319 AM MST SUN NOV 22 2009/
DISCUSSION...A POTENT WEATHER SYSTEM IS MOVING THROUGH THE
PACIFIC NORTHWEST EARLY THIS MORNING...AND WILL PRODUCE
WIDESPREAD SNOW SHOWERS ACROSS THE NORTHERN ROCKIES TODAY. THE
HEAVIEST SNOW WILL DEVELOP OVER NORTHERN IDAHO AND THE
BITTERROOTS FROM MID MORNING THROUGH EARLY AFTERNOON AHEAD OF A
SURFACE COLD FRONT. HOWEVER...GOOD OROGRAPHIC LIFT AND INSTABILITY
WILL CONTINUE THE SHOWERS IN THOSE LOCATIONS THROUGH THE DAY AND
INTO THE EVENING. LIGHTER SNOW ACCUMULATIONS ARE EXPECTED
THROUGHOUT THE REMAINDER OF WESTERN MONTANA.
WINDS WILL INCREASE AS THE FRONT APPROACHES AND REMAIN UP INTO THE
EVENING. WINDS IN THE GRANGEVILLE AREA ARE EXPECTED TO REACH
ADVISORY CRITERIA (IN EXCESS OF 30 MPH WITH GUSTS INTO THE 40S) EARLY
THIS MORNING THROUGH MIDDAY AS THE WINDS IN THE LOWER ATMOSPHERE
AND THE SURFACE PRESSURE GRADIENT INCREASE. WINDS IN THE MOUNTAINS
NEAR GRANGEVILLE HAVE BEEN GUSTING TO WELL ABOVE 40 MPH ALREADY.
THE SOUTHERLY WINDS GENERALLY INHIBIT SHOWER ACTIVITY OVER THE
CAMAS PRAIRIE...BUT THE FRONT MAY BE STRONG ENOUGH TO OVERCOME THE
DOWNSLOPING. THEREFORE...EXPECT SOME BLOWING SNOW IN THAT
AREA AS WELL AS IN THE CLEARWATER AND BITTERROOT MOUNTAINS WITH
THE PASSAGE OF THE FRONT.
HIGH PRESSURE WILL BUILD OVER THE AREA MONDAY AND MONDAY NIGHT.
HOWEVER...THE FLOW WILL STILL CONTAIN SUBSTANTIAL MOISTURE.
THEREFORE...LIGHT SNOW SHOWERS ARE POSSIBLE ACROSS NORTHWEST
MONTANA...AND SOME CLOUD COVER IS EXPECTED OVER WEST CENTRAL
MONTANA AND NORTH CENTRAL IDAHO.
TUESDAY THROUGH THE WEEK...HIGH PRESSURE RIDGING IS STILL THE MAIN
FEATURE FOR THE EXTENDED FORECAST PERIOD. WHILE THIS PATTERN ALLOWS
FOR A DRIER AND MUCH TAMER TREND IN WEATHER...ONE IMPACT THAT WILL
CONTINUE TO BE MONITORED WILL BE FOG DEVELOPMENT UNDER THE
STRENGTHENING RIDGE. AS THE NORTHERN ROCKIES FALLS UNDER
INCREASINGLY STABLE AIR AND RESULTING INVERSIONS DEVELOP BY
MIDWEEK...FOG FORMATION IN VALLEYS OF WESTERN MONTANA AND CENTRAL
IDAHO WILL BE KEY...PARTICULARLY FOR ANY HOLIDAY TRAVEL. AS OF
RIGHT NOW...THE BEST DAYS FOR FOG FORMATION WILL BE WEDNESDAY
MORNING AND AGAIN ON THURSDAY MORNING. ANY INVERSIONS THAT FORM
AND HELP KEEP FOG TRAPPED IN VALLEYS WILL DEPEND ON THE STRENGTH
AND POSITION OF THE RIDGE...WHICH WILL ALL NEED TO BE MONITORED
AS TIME PASSES.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT... WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR LOWER
CLARK FORK REGION.
ID...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
OROFINO/GRANGEVILLE REGION.
WIND ADVISORY UNTIL NOON PST TODAY FOR LOWER HELLS CANYON/SALMON
RIVER REGION-OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...PALLISTER
LONG TERM....WHITMORE
AVIATION...PALLISTER
000
FXUS65 KTFX 221217
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
517 AM MST SUN NOV 22 2009
.DISCUSSION...
TODAY THROUGH TUESDAY...A MOIST PACIFIC WEATHER SYSTEM CURRENTLY
OVER THE PACIFIC NORTHWEST WILL MOVE EAST INTO THE NORTHERN
ROCKIES TODAY. SNOW SHOWERS WILL BEGIN IN THE MOUNTAINS OF
WESTERN MONTANA LATER THIS MORNING...THEN THEY WILL SPREAD INTO
THE MOUNTAINS OF SOUTHWEST AND CENTRAL MONTANA FOR THIS AFTERNOON
AND EVENING. THE SYSTEM WILL WEAKEN AND BEGIN TO SPLIT AS IT MOVES
INTO THE AREA...WHICH WILL MOVE THE BEST CHANCE FOR ACCUMULATING
SNOW AT LOWER ELEVATIONS INTO SOUTHWEST MONTANA. THE STRONGEST
OROGRAPHIC LIFT WILL BE IN THE MOUNTAIN AREAS OF MADISON AND
GALLATIN COUNTIES. HAVE THEREFORE GONE WITH A WINTER WEATHER
ADVISORY FOR SNOW THERE...AS 2 TO 4 INCHES OF SNOWFALL ARE
POSSIBLE IN THE VALLEYS WITH 5 TO 9 INCHES EXPECTED IN THE
MOUNTAINS. BREEZY SOUTHERLY WINDS THIS AFTERNOON WILL SHIFT MORE
WESTERLY THIS EVENING...CAUSING AREAS OF BLOWING SNOW THROUGH
FAVORED VALLEYS. LESSER AMOUNTS ARE EXPECTED ACROSS THE REMAINDER
OF SOUTHWEST MONTANA. ACCUMULATING SNOW WILL ALSO OCCUR IN THE
MOUNTAINS OF THE ROCKY MOUNTAIN FRONT...BUT IT SHOULD BE LIMITED
TO AREAS ABOVE 5000 FEET DUE TO INCREASING WESTERLY DOWNSLOPE
WINDS. DOWNSLOPE WINDS WILL ALSO LIMIT RAIN AND SNOW SHOWERS OVER
THE PLAINS. LINGERING SNOW SHOWERS WILL DECREASE OVERNIGHT AS THE
SYSTEM EXITS THE AREA. AN UPPER LEVEL HIGH PRESSURE RIDGE WILL
BUILD INTO THE AREA FOR MONDAY THROUGH TUESDAY. A WEAK
DISTURBANCE WILL MOVE THROUGH THE RIDGE MONDAY AND BRING A CHANCE
OF SNOW SHOWERS TO THE MOUNTAINS. A STRONGER SHORTWAVE TROUGH WILL
THEN FLATTEN THE RIDGE MONDAY NIGHT INTO TUESDAY. THIS WILL BRING
A CHANCE OF SNOW SHOWERS TO THE MOUNTAINS ONCE AGAIN...BUT IT WILL
ALSO BRING STRONG WESTERLY DOWNSLOPE WINDS TO THE PLAINS. THIS MAY
REQUIRE HIGH WIND HIGHLIGHTS...BUT WILL CONTINUE TO MONITOR THE
SITUATION. NEAR NORMAL TEMPERATURES TODAY WILL WARM TO AROUND 10
DEGREES ABOVE NORMAL BY TUESDAY. COULSTON
TUESDAY NIGHT THROUGH SUNDAY NIGHT...BOTH THE ECMWF AND GFS
COMPUTER MODEL RUNS ARE IN GOOD AGREEMENT INTO FRIDAY BUT DIVERGE
WITH THEIR SOLUTIONS THEREAFTER. FOR TUESDAY NIGHT A STRONG UPPER
RIDGE WILL BE APPROACHING THE AREA. THERE COULD BE A FEW SNOW
SHOWERS WITH LINGERING MOISTURE IN THE NORTHWEST FLOW ALOFT. THE
STRONG UPPER RIDGE WILL BE OVER THE AREA WEDNESDAY AND THURSDAY
FOR GENERALLY DRY CONDITIONS WITH TEMPERATURES WELL ABOVE NORMAL
OVER THE PLAINS. RAISED HIGH TEMPERATURES FOR THANKSGIVING 5 TO
10 DEGREES OVER THE PLAINS. IN FACT HIGH TEMPERATURES APPROACHING
RECORD LEVELS ARE NOT OUT OF THE QUESTION. AN UPPER TROUGH IS
FORECAST TO MOVE INTO THE AREA FRIDAY NIGHT AND MODELS HAVE COME
INTO BETTER AGREEMENT ON THE TIMING OF THIS FEATURE. AS THE UPPER
TROUGH MOVES INTO THE AREA EXPECT INCREASING CHANCES OF
PRECIPITATION ALONG WITH COOLER TEMPERATURES. AS WAS MENTIONED
BEFORE MODELS DIFFER LATER IN THE WEEKEND INTO EARLY NEXT WEEK.
INHERITED CHANCES OF PRECIPITATION LOOK REASONABLE AS THEY ARE A
COMPROMISE BETWEEN THE DRIER ECMWF RUN AND THE WETTER GFS RUN.
BLANK
&&
.AVIATION...
UPDATED 1155Z.
ANOTHER PACIFIC WEATHER SYSTEM WILL MOVE THROUGH THE FORECAST
AREA OVERNIGHT. IN ADVANCE OF THIS WEATHER SYSTEM MOISTURE WILL
BE INCREASING FROM THE WEST TODAY. SNOW SHOULD REACH THE WESTERN
MOUNTAINS AROUND MID-MORNING THEN SPREAD OVER SOUTHWEST MONTANA
FROM THEN THROUGH EARLY AFTERNOON. EXPECT MOUNTAINS TO BE TOTALLY
OBSCURED AT TIMES. VALLEYS IN SOUTHWEST MONTANA WILL SEE A PERIOD
OF MVFR/IFR CONDITIONS IN THE SNOW. THE PLAINS WILL SEE
ISOLATED/SCATTERED SNOW SHOWERS THIS AFTERNOON THROUGH THIS
EVENING BUT CONDITIONS ARE EXPECTED TO BE VFR WITH THE EXCEPTION
OF POSSIBLE MVFR CONDITIONS NEAR KLWT. WOULD NOT BE SURPRISED IF
SOUTHWEST TO WEST WINDS ARE A LITTLE STRONGER THAN FORECAST THIS
AFTERNOON INTO TONIGHT. DO NOT HAVE REAL GOOD CONFIDENCE ON THE
TIMING OF THE SNOW FOR THE KBZN TAF. SOME GUIDANCE SUGGESTS SNOW
WILL BE DURING THE 18Z-00Z TIME FRAME WHILE OTHER GUIDANCE
SUGGESTS SNOW WILL BE MORE IN THE 21Z-03Z TIME FRAME. BLANK
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 40 28 44 31 / 20 20 10 10
CTB 39 26 43 30 / 20 20 10 10
HLN 40 24 42 24 / 50 30 10 10
BZN 35 16 34 12 / 100 60 10 20
WEY 28 12 27 10 / 100 80 30 30
DLN 33 14 30 13 / 90 40 10 10
HVR 44 24 45 26 / 30 20 10 10
LWT 38 23 38 25 / 40 40 10 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 11 AM THIS MORNING TO 11 PM MST
THIS EVENING FOR MTZ015-055.
&&
$$
SHORT TERM...COULSTON
LONG TERM...BLANK
AVIATION...BLANK
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 221029
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
329 AM MST SUN NOV 22 2009
.SHORT TERM...VALID FOR TDY AND MON...
A STORM SYSTEM OVER THE PACIFIC NORTHWEST WILL MOVE THROUGH THE
AREA THIS AFTERNOON AND TONIGHT...WITH BRIEF RIDGING DEVELOPING
ON MONDAY. THE MAIN CORE OF THE SYSTEM WILL MOVE FROM
WASHINGTON...ACROSS SOUTHERN IDAHO AND INTO WYOMING. THIS TRACK
PUTS THE AREA UNDER STRONGLY DIVERGENT SOUTHWEST FLOW ALOFT BY
LATE THIS MORNING...CONTINUING INTO THE EVENING. ALTHOUGH A GOOD
CHUNK OF THE UPPER ENERGY ASSOCIATED WITH THE SYSTEM STAYS SOUTH
OF THE AREA...INSTABILITY COMBINED WITH GOOD PACIFIC MOISTURE AND
THE DIVERGENCE ALOFT LOOKS TO BE ENOUGH TO GENERATE PRECIPITATION
OVER WESTERN AREAS LATE THIS MORNING...SPREADING INTO EASTERN
AREAS TONIGHT. THE PRESSURE GRADIENT WITH THIS SYSTEM IS STRONG
AND WILL RESULT IN SOME GUSTY WEST TO SOUTHWEST WINDS TODAY. THIS
WILL RETARD PRECIPITATION OVER LOWER ELEVATIONS UNTIL LATE IN THE
DAY. ONCE THE SUN SETS...THE DOWNSLOPE INFLUENCE WILL DECREASE
ALLOWING FOR MORE SCATTERED PRECIPITATION TO DEVELOP OVER THE
PLAINS. MOUNTAIN LOCATIONS LOOK TO PICK UP A QUICK 5 TO 7 INCHES
WITH THIS SYSTEM...PARTICULARLY ON WEST FACING SLOPES. THE
EASTERN PORTION OF THE SHIELDS AND PARADISE VALLEYS COULD SEE 2
TO 3 INCHES LATE TODAY INTO THE EVENING AS WELL...WITH UPSLOPE
WINDS INTO THOSE AREAS. THE PATTERN DOESN`T FAVOR MUCH IF ANY SNOW
ACCUMULATION ALONG THE BEARTOOTH FOOTHILLS AS WINDS REMAIN
WESTERLY. PLAINS LOCATIONS SHOULD STAY UNDER AN INCH FOR MOST
LOCATIONS. TEMPERATURES TODAY WILL STAY NEAR 40 DEGREES IN THE
WEST WITH CLOUD COVER BUILDING IN THIS MORNING. WITH CLEAR SKIES
TO START THE DAY EASTERN AREAS SHOULD PUSH INTO THE UPPER 40S.
WINDS OF 15 TO 30 MPH WILL BE COMMON OVER WESTERN AREAS
TODAY...WITH STRONGER WINDS POSSIBLE IN THE FAVORED AREAS FROM
LIVINGSTON TO NYE AS THE PRESSURE GRADIENT TIGHTENS ACROSS THE
AREA.
TONIGHT THE SOUTH CENTRAL AND SOUTHEAST PORTIONS OF THE FORECAST
AREA WILL SEE THE BEST CHANCES FOR PRECIPITATION. GIVEN THE
FORECAST TRACK TAKING THE BULK OF THE SYSTEM SOUTHEAST THROUGH
WYOMING...KEPT POPS IN THE CHANCE RANGE. IF THE SYSTEM TRACKS A
BIT FURTHER NORTH COULD NEED TO BUMP AREAS FROM SHERIDAN AND
SOUTHERN BIG HORN COUNTY...OVER TO CARTER COUNTY UP TO LIKELY
OVERNIGHT. SUNDAYS SYSTEM PUSHES OUT OF THE AREA MONDAY LEAVING
CLEARING SKIES AND GUSTY NORTHWEST WINDS OVER THE AREA.
TEMPERATURES WILL BE NEAR SEASONAL LEVELS IN THE 30S AND LOWER
40S. CHAMBERS
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
THE EXTENDED PERIOD BEGINS TUESDAY MORNING WITH GENERALLY FAIR
AGREEMENT BETWEEN THE GFS AND ECMWF. THE EVOLUTION OF THE GFS
LATE IN THE EXTENDED PERIOD APPEARS SUSPECT. THEREFORE...TRENDED
INHERITED FORECASTS TOWARD THE ECMWF. AN UPPER-LEVEL TROUGH
PASSES EAST OF THE CWA LATE TUESDAY INTO EARLY WEDNESDAY.
ADJUSTED POPS TO COVER MAINLY EASTERN ZONES AND THE HIGHER
TERRAIN DURING THIS TIME. AN UPPER-LEVEL RIDGE BUILDS OVER THE
WESTERN CONUS THROUGH THE REMAINDER OF THE WORK WEEK. LIMITED
POPS AND WARMED TEMPERATURE FORECASTS SLIGHTLY THROUGH FRIDAY IN
RESPONSE. THE NEXT UPPER-TROUGH PASSES THROUGH THE REGION LATE
FRIDAY THROUGH EARLY SUNDAY. MADE MINOR ADJUSTMENTS TO POPS AND
TEMPERATURE FORECASTS DURING THIS TIME. SCHUKNECHT
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL OVERNIGHT ACROSS THE FORECAST AREA.
AN UPPER-LEVEL DISTURBANCE WILL IMPACT WESTERN ZONES BY MID-
MORNING. SCATTERED SHOWERS WILL BE POSSIBLE AND MAY PRODUCE
PERIODS OF MVFR CONDITIONS AND MOUNTAIN OBSCURATION. SHOWERS ARE
EXPECTED TO SPREAD EASTWARD THIS EVENING INTO EARLY MONDAY.
STRONG WINDS ALONG THE BEARTOOTH FOOTHILLS WEST INTO KLVM ARE
EXPECTED TO DEVELOP BY MID-MORNING. EXPECT SUSTAINED WINDS AROUND
25 KTS WITH GUSTS UP TO 40 KTS THROUGH THIS AFTERNOON FOR THESE
LOCATIONS. SCHUKNECHT
&&
.PRELIMINARY POINT TEMP/POPS...
TDY MON TUE WED THU FRI SAT
-------------------------------------------------------
BIL 042 026/040 025/047 030/047 031/055 033/055 033/046
2/W 41/B 00/B 10/B 00/U 01/B 22/W
LVM 036 017/034 016/042 023/048 027/054 028/050 026/041
6/J 62/J 01/N 10/B 00/N 02/W 32/W
HDN 045 025/043 022/049 028/048 028/056 030/056 030/049
2/W 42/J 00/B 10/B 00/U 01/B 22/W
MLS 046 026/043 023/048 025/044 025/053 030/055 032/047
0/U 32/J 00/B 20/B 00/U 01/B 22/W
4BQ 045 025/040 022/046 025/043 024/052 029/055 030/047
0/U 42/W 01/B 20/B 00/U 01/U 22/W
BHK 044 023/040 022/044 024/040 021/051 027/052 029/046
0/U 22/W 01/B 20/B 00/U 01/B 22/W
SHR 044 024/038 017/047 025/046 024/054 027/055 025/046
2/W 42/J 00/B 21/B 10/U 01/B 22/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KMSO 221019
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
319 AM MST SUN NOV 22 2009
.DISCUSSION...A POTENT WEATHER SYSTEM IS MOVING THROUGH THE
PACIFIC NORTHWEST EARLY THIS MORNING...AND WILL PRODUCE
WIDESPREAD SNOW SHOWERS ACROSS THE NORTHERN ROCKIES TODAY. THE
HEAVIEST SNOW WILL DEVELOP OVER NORTHERN IDAHO AND THE
BITTERROOTS FROM MID MORNING THROUGH EARLY AFTERNOON AHEAD OF A
SURFACE COLD FRONT. HOWEVER...GOOD OROGRAPHIC LIFT AND INSTABILITY
WILL CONTINUE THE SHOWERS IN THOSE LOCATIONS THROUGH THE DAY AND
INTO THE EVENING. LIGHTER SNOW ACCUMULATIONS ARE EXPECTED
THROUGHOUT THE REMAINDER OF WESTERN MONTANA.
WINDS WILL INCREASE AS THE FRONT APPROACHES AND REMAIN UP INTO THE
EVENING. WINDS IN THE GRANGEVILLE AREA ARE EXPECTED TO REACH
ADVISORY CRITERIA (IN EXCESS OF 30 MPH WITH GUSTS INTO THE 40S) EARLY
THIS MORNING THROUGH MIDDAY AS THE WINDS IN THE LOWER ATMOSPHERE
AND THE SURFACE PRESSURE GRADIENT INCREASE. WINDS IN THE MOUNTAINS
NEAR GRANGEVILLE HAVE BEEN GUSTING TO WELL ABOVE 40 MPH ALREADY.
THE SOUTHERLY WINDS GENERALLY INHIBIT SHOWER ACTIVITY OVER THE
CAMAS PRAIRIE...BUT THE FRONT MAY BE STRONG ENOUGH TO OVERCOME THE
DOWNSLOPING. THEREFORE...EXPECT SOME BLOWING SNOW IN THAT
AREA AS WELL AS IN THE CLEARWATER AND BITTERROOT MOUNTAINS WITH
THE PASSAGE OF THE FRONT.
HIGH PRESSURE WILL BUILD OVER THE AREA MONDAY AND MONDAY NIGHT.
HOWEVER...THE FLOW WILL STILL CONTAIN SUBSTANTIAL MOISTURE.
THEREFORE...LIGHT SNOW SHOWERS ARE POSSIBLE ACROSS NORTHWEST
MONTANA...AND SOME CLOUD COVER IS EXPECTED OVER WEST CENTRAL
MONTANA AND NORTH CENTRAL IDAHO.
TUESDAY THROUGH THE WEEK...HIGH PRESSURE RIDGING IS STILL THE MAIN
FEATURE FOR THE EXTENDED FORECAST PERIOD. WHILE THIS PATTERN ALLOWS
FOR A DRIER AND MUCH TAMER TREND IN WEATHER...ONE IMPACT THAT WILL
CONTINUE TO BE MONITORED WILL BE FOG DEVELOPMENT UNDER THE
STRENGTHENING RIDGE. AS THE NORTHERN ROCKIES FALLS UNDER
INCREASINGLY STABLE AIR AND RESULTING INVERSIONS DEVELOP BY
MIDWEEK...FOG FORMATION IN VALLEYS OF WESTERN MONTANA AND CENTRAL
IDAHO WILL BE KEY...PARTICULARLY FOR ANY HOLIDAY TRAVEL. AS OF
RIGHT NOW...THE BEST DAYS FOR FOG FORMATION WILL BE WEDNESDAY
MORNING AND AGAIN ON THURSDAY MORNING. ANY INVERSIONS THAT FORM
AND HELP KEEP FOG TRAPPED IN VALLEYS WILL DEPEND ON THE STRENGTH
AND POSITION OF THE RIDGE...WHICH WILL ALL NEED TO BE MONITORED
AS TIME PASSES.
&&
.AVIATION...ANOTHER ACTIVE WEATHER DAY IS EXPECTED WITH AN UPPER
TROUGH AND COLD FRONTAL PASSAGE. THE FRONT WILL MOVE THROUGH
NORTHERN IDAHO BY MIDDAY THEN THROUGH WESTERN MONTANA BY LATE
AFTERNOON. WIDESPREAD SNOW SHOWERS WILL RESULT...SOME HEAVY AT
TIMES. INCREASED WEST WINDS WILL ALSO BE OF CONCERN. SHOWERS WILL
BEGIN TO DECREASE BY LATE AFTERNOON...BUT LINGER WELL INTO THE
EVENING MAINLY OVER NORTHERN IDAHO AND THE BITTERROOT MOUNTAINS.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 11 PM MST THIS
EVENING FOR BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 11 PM MST THIS
EVENING FOR LOWER CLARK FORK REGION.
ID...WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 10 PM PST THIS
EVENING FOR OROFINO/GRANGEVILLE REGION.
WIND ADVISORY UNTIL NOON PST TODAY FOR LOWER HELLS CANYON/SALMON
RIVER REGION-OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY FROM 7 AM THIS MORNING TO 10 PM PST THIS
EVENING FOR NORTHERN CLEARWATER MOUNTAINS-SOUTHERN
CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...WHITMORE
LONG TERM....ALLEGRETTO
AVIATION...WHITMORE
000
FXUS65 KGGW 221013
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
313 AM MST SUN NOV 22 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...
A NARROW RIDGE MOVING OVER EASTERN MONTANA WILL START THE DAY OFF
WITH SUNSHINE AND MUCH QUIETER SOUTHERLY WINDS. THE RIDGE WILL BE
PUSHED ASIDE BY THE NEXT UPPER TROUGH THAT CAN BE SEEN ON THE GOES
WATER VAPOR IMAGERY SLAMMING INTO THE NORTHWEST COAST. AN
ASSOCIATED WEAK WARM FRONT WILL BEGIN TO INCREASE CLOUD COVER FROM
THE WEST THIS AFTERNOON. MOISTURE WILL MAKE OVER THE DIVIDE AND
INTO CENTRAL MONTANA BY LATE AFTERNOON. LEFT SLIGHT CHANCE POPS
IN THE FAR WESTERN ZONES FOR RAIN AND SNOW BUT EXPECT VERY LITTLE
TO HIT THE GROUND.
TONIGHT...THE UPPER TROUGH DIVES SOUTHEAST INTO NORTHERN COLORADO
BY LATE TONIGHT TAKING MOST ENERGY TO OUR SOUTH. A VORT MAX
CENTERED OVER SOUTHEASTERN MONTANA COULD SPREAD LIGHT SNOW SHOWER
ACTIVITY NORTH INTO OUR SOUTHERN ZONES BUT NOT MUCH ACCUMULATION
IS EXPECTED SINCE THE LOWER ATMOSPHERE REMAINS DRY. WILL GO WITH
SLIGHT CHANCE POPS. CLOUD COVER WILL PREVENT OVERNIGHT
TEMPERATURES FROM PLUNGING TOO LOW.
MONDAY...GENERAL TROUGHINESS WILL MAINTAIN COOL CONDITIONS AND
CLOUD COVER. HOWEVER HIGHS WILL STILL BE SLIGHTLY ABOVE AVERAGE
FOR THIS TIME OF YEAR. NOT MUCH IN THE WAY OF PRECIPITATION IS
EXPECTED EITHER. BUT WILL KEEP SLIGHT CHANCE POPS IN SOUTHERN
ZONES AS A WEAK FRONT AND DYNAMICS GENERATE SOME SHOWERS JUST
SOUTH OF OUR SOUTHERN CWA BORDER.
MONDAY NIGHT...AN UPPER RIDGE THEN LEANS OVER OUR AREA TO BRING
WAA AND CLEARING SKIES. OVERNIGHT LOWS WILL DROP A LITTLE LOWER
WITH RADIATIONAL COOLING. BUT WARM AIR ALOFT WILL SURGE IN FROM
THE WEST...MODERATING THE LOWS.
TUESDAY...LATE AFTERNOON A COMPACT CYCLONE WILL DEVELOP NEAR THE
BORDER BETWEEN SASKATCHEWAN AND MANITOBA. THIS STORM WILL SEND A
DRY COLD FRONT SOUTH INTO OUR AREA. THIS WILL VEER WINDS AROUND TO
THE NORTHWEST BUT MIGHT BE TOO LATE IN THE DAY TO BRING ANY REAL
STRONG WINDS TO THE AREA. SCT
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
MODELS SHOW GOOD AGREEMENT UNTIL A COLD FRONT MOVES THROUGH THE
AREA FRIDAY NIGHT. A SHORTWAVE TROUGH WILL DIVE SOUTHEAST THROUGH
THE DAKOTAS TUESDAY NIGHT AND WEDNESDAY BRINGING SOMEWHAT COOLER
AIR MAINLY TO THE EASTERN ZONES FOR WEDNESDAY. IT LOOKS LIKE THE
PRECIPITATION WITH THIS SYSTEM WILL STAY TO THE EAST.
UPPER RIDGE BUILDS INTO MONTANA FOR THANKSGIVING DAY GIVING THE
FORECAST AREA A WARM AND DRY DAY. THE WARM TEMPERATURES WILL
LINGER THROUGH FRIDAY AS THE RIDGE MOVES EAST.
A COLD FRONT WILL PASS THROUGH EASTERN MONTANA FRIDAY NIGHT WITH
AN UPPER TROUGH ON SATURDAY. ENOUGH MOISTURE CURRENTLY FORECASTED
WITH THIS SYSTEM TO WARRANT A SLIGHT CHANCE OF RAIN AND SNOW.
WHILE THE ECMWF MOVES THE TROUGH TO THE EAST NEXT SUNDAY AND
BRINGS ANOTHER UPPER RIDGE WITH WARMER TEMPERATURES INTO THE
STATE... THE GFS LINGERS THE TROUGH OVER THE AREA AND HAS MUCH
COLDER AIR DROPPING IN FROM CANADA. GIVEN THE WARM PATTERN OF
LATE...WILL SIDE TOWARDS THE WARMER ECMWF FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. WILL SEE CLEAR SKIES THIS MORNING WITH LIGHT
MAINLY SOUTHEAST WINDS. MID AND HIGH CLOUDS WILL MOVE IN FROM THE
WEST THIS AFTERNOON AND BECOME A BROKEN TO OVERCAST MID LEVEL DECK
BY THIS EVENING. MAY SEE A FEW FLURRIES TONIGHT AS A COLD FRONT
TURNS WINDS TO THE NORTHWEST AT 5 TO 10 KNOTS. FORRESTER
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 220600
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 PM MST SAT NOV 21 2009
UPDATED AVIATION DISCUSSION
.UPDATE...
AN UPDATE FOR REMOVING SOME PRECIPITATION AREAS ACROSS NORTH
CENTRAL AND CENTRAL MONTANA. THE DISTURBANCE THAT MOVED THROUGH
NORTH CENTRAL MONTANA HAS TAKEN ITS PRECIP INTO NORTHEAST MONTANA.
PARTLY CLOUDY AND BREEZY CONDITIONS REMAIN. ALSO REDUCED PRECIP
CHANCES IN THE SOUTHWEST. AGAIN...THE AREA OF PRECIP HAS
DIMINISHED AND EXPECT THIS TREND TO CONTINUE INTO EARLY MORNING
HOURS. ALSO DROPPED TEMPS A BIT OVER CENTRAL MONTANA. CLEAR SKIES
AND DRY AIR IS DROPPING TEMPS INTO MID 20S. EXPECT WINDS TO
CONTINUE STRONG ENOUGH SO THAT MUCH MORE COOLING DOES NOT
OCCUR...BUT SUFFICIENT TO DROP THE TEMPS A BIT. NO OTHER CHANGES. DB
&&
.AVIATION...
UPDATED 0600Z.
A WEAK UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
EVENING...ALLOWING FOR GENERALLY CLEAR/PARTLY CLOUDY SKIES OVER THE
REGION. THE NEXT PACIFIC STORM WILL MOVE INTO THE ROCKY MOUNTAIN
FRONT AND SOUTHWEST MONTANA AFTER 17Z SUNDAY...AND THEN CONTINUE TO
AFFECT THE REGION THROUGH SUNDAY EVENING. VFR CONDITIONS ARE
EXPECTED ON SUNDAY MORNING...HOWEVER...THEY WILL GRADUALLY LOWER TO
IFR/LIFR CONDITIONS OVER THE REGION DURING THE EARLY AFTERNOON HOURS
ON SUNDAY. EXPECT MOUNTAINS TO BE OBSCURED AFTER 16Z SUNDAY. EXPECT
MOST OF THE WIDESPREAD PRECIP TO COME TO AN END BY 03Z MONDAY...WITH
A FEW LINGERING SNOW SHOWERS...MAINLY OVER THE MOUNTAINS UNTIL 12Z
MONDAY. BRUSDA
&&
.PREV DISCUSSION...
/ISSUED 500 PM MST SAT NOV 21 2009/
THE UPPER LEVEL TROUGH THAT MOVED THROUGH HE REGION EARLIER TODAY
WILL EXIT IT THE REGION TONIGHT FOLLOWED BY A BRIEF PERIOD OF
DRYING UNDER WEAK UPPER LEVEL RIDGING. WIDELY SCATTERED SNOW
SHOWERS OVER THE MTNS WILL DIMINISH EARLY THIS EVENING WITH A FEW
ISOLATED SNOW SHOWERS POSSIBLE THROUGH EARLY THIS EVENING AS WELL
ALONG THE CANADIAN BORDER IN ASSOCIATION WITH A WEAK DISTURBANCE
MOVING SOUTHEAST FROM ALBERTA. CLOUDS AND MOISTURE WILL INCREASE
AGAIN ON SUNDAY AS A VIGOROUS PACIFIC STORM SYSTEM MOVES ONSHORE
AND QUICKLY MOVES TO THE NORTHERN ROCKIES BY SUNDAY EVENING AND
ACROSS THE STATE SUNDAY NIGHT. THIS SYSTEM WILL BRING ANOTHER
PERIOD OF SNOW TO THE MOUNTAINS SUNDAY AFTERNOON AND EVENING WITH
SNOW SHOWERS POSSIBLE ELSEWHERE. MOIST AND UNSTABLE WEST TO
NORTHWEST FLOW WILL MAINTAIN AT LEAST A CHANCE OF SNOW SHOWERS OVER
THE CENTRAL AND SW MT MTNS THROUGH SUNDAY NIGHT. ACCUMULATIONS OF AN
INCH OR LESS ARE EXPECTED ACROSS THE VALLEYS OF SW MT WITH 1 TO 3
INCHES POSSIBLE IN THE MTNS. THE MOST PERSISTENT SNOW WILL OCCUR
OVER THE GALLATIN AND MADISON MTN RANGES WHERE HIGHER AMOUNTS OF 3
TO 5 INCHES APPEAR LIKELY FOR ELEVATIONS ABOVE 6000 FT THROUGH
SUNDAY NIGHT. UPPER LEVEL RIDGING BUILDS IN BEHIND THIS SYSTEM ON
MONDAY FOR DRIER CONDITIONS. TEMPERATURES WILL REMAIN SEASONABLY
COOL THROUGH MONDAY WITH CLEARING SKIES TONIGHT ALLOWING TEMPS TO
DROP INTO THE SINGLE DIGITS OR LOWER IN SOME OF THE SW MT VALLEYS.
HOENISCH
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 22 38 29 42 / 0 20 20 0
CTB 22 36 28 40 / 0 20 20 0
HLN 22 38 28 39 / 0 40 30 10
BZN 9 36 17 35 / 0 60 40 10
WEY 3 27 11 26 / 30 90 80 20
DLN 13 31 16 30 / 0 60 40 0
HVR 19 41 25 45 / 20 20 10 10
LWT 19 37 22 38 / 0 40 40 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
000
FXUS65 KBYZ 220352
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
852 PM MST SAT NOV 21 2009
.EVENING UPDATE...
FORECAST FOR TONIGHT LOOKS TO BE IN GOOD SHAPE AND HAVE ONLY MADE
A FEW MINOR ADJUSTMENTS. UPPER LEVEL SYSTEM AND TROUGH THAT
BROUGHT THE ISOLATED SHOWERS TO THE AREA TODAY HAS SHIFTED INTO
THE DAKOTAS SO HAVE REMOVED POP CHANCES FROM THE SOUTHEAST ZONES.
STILL SOME LINGERING CLOUDS AND LIGHT SNOW SHOWERS ACROSS THE
MOUNTAINS SO HAVE KEPT POPS ACROSS THESE AREAS BUT LOWERED THEM
FOR THE REMAINDER OF THE EVENING. RIDGING BUILDS IN LATE TONIGHT
INTO SUNDAY MORNING FOR A SHORT PERIOD BEFORE ANOTHER TROUGH
MOVES ACROSS THE FORECAST AREA SUNDAY AFTERNOON. LEE-SIDE
TROUGHING WILL DEVELOP AHEAD OF THIS WAVE LATE TONIGHT BRINGING A
RETURN TO WINDY CONDITIONS TO THE UPPER YELLOWSTONE AND
STILLWATER VALLEYS. PRESSURE GRADIENTS TIGHTEN BUT ARE NOT
ORIENTED FAVORABLY FOR HIGH WINDS SO WILL KEEP WINDS JUST BELOW
ADVISORY CRITERIA FOR NOW. THERE WILL BE MORE CLEARING TONIGHT
THAN LAST NIGHT SO COOLER OVERNIGHT LOWS CAN BE EXPECTED. GIVEN
THAT WINDS WILL CONTINUE FROM BILLINGS WESTWARD AND ESPECIALLY
THE LIVINGSTON AREA THROUGHOUT THE NIGHT...HAVE BUMPED UP LOW
TEMPERATURES ACROSS THESE LOCATIONS. UPDATE OUT SHORTLY. HOOLEY
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
JUST SOME MINOR CHANGES MADE TO THE EXTENDED FORECAST THIS
AFTERNOON. UPPER LEVEL RIDGE WILL BE OVER THE FORECAST TUESDAY
MORNING AND HAVE DRIED OUT MOST PERIODS FOR THIS PERIOD. UPPER
LEVEL TROUGH SLIDES INTO NORTH DAKOTA TUESDAY AFTERNOON AND
TUESDAY NIGHT WITH SOME WEAK ENERGY MOVING INTO THE FORECAST AREA
AT THIS TIME. MODELS DO HINT AT A LITTLE PRECIP FOR THIS WEAK
SYSTEM SO HAVE SPREAD THE LOW POPS A LITTLE FARTHER WEST. DID ADD
POPS FOR THE CENTRAL AND WESTERN ZONES AS WELL FOR TUESDAY NIGHT.
THIS SYSTEM QUICKLY EXITS BY WEDNESDAY MORNING LEAVING DRY
CONDITIONS AND WARMER TEMPS THROUGH MUCH OF FRIDAY. MODELS BRING
IN THE NEXT SYSTEM ACROSS SOUTHERN CANADA ON FRIDAY NIGHT AND
SATURDAY WHERE THE ECMWF BRINGS THE SYSTEM RIGHT OVER THE
FORECAST AREAS. HAVE KEPT IN LOW POPS FOR MOST AREAS FOR NOW
UNTIL THE MODELS COME INTO BETTER AGREEMENT. SOLUM
&&
.AVIATION...
A WEAK RIDGE OF HIGH PRESSURE WILL MOVE ACROSS THE AREA TONIGHT
AND WILL BRING VFR CONDITIONS. AN UPPER TROUGH OF LOW PRESSURE
WILL BEGIN MOVING INTO THE WESTERN AREAS LATE SUNDAY MORNING. THE
AREA OF LOW PRESSURE WILL BRING ISOLATED RAIN AND SNOW SHOWERS TO
KLVM WITH OCCASIONAL MVFR CONDITIONS EXPECTED. SCATTERED SNOW
SHOWERS WILL BE OVER THE MOUNTAINS WHICH WILL BRING OCCASIONAL
MOUNTAIN OBSCURATION. ISOLATED SHOWERS WILL MOVE INTO THE THE
CENTRAL AND EASTERN PLAINS BY 19Z. GUSTY WINDS OF 25 MPH TO 35
MPH WITH GUSTS TO NEAR 50 MPH WILL DEVELOP ALONG THE FOOTHILLS OF
THE BEARTOOTH AND ABSAROKA MOUNTAINS BY 18Z. THESE WINDS WILL
DIMINISH BY EVENING. RICHMOND
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 024/040 028/042 024/046 029/051 031/055 034/051 033/044
02/J 21/B 12/W 20/B 00/U 02/W 22/W
LVM 022/036 023/035 018/043 027/050 030/054 030/046 030/044
04/J 32/S 12/W 20/B 00/U 03/W 32/W
HDN 022/043 024/044 019/047 025/052 028/057 029/053 027/049
02/W 22/O 12/W 20/B 00/U 02/W 22/W
MLS 021/045 024/043 020/047 023/046 026/056 030/051 031/042
01/B 22/O 22/W 00/B 00/U 02/W 22/W
4BQ 020/042 021/042 019/045 022/046 025/056 028/051 028/044
01/N 23/O 12/W 20/B 00/U 02/W 22/W
BHK 020/045 021/040 019/043 023/040 025/054 026/051 028/043
11/B 22/O 22/W 00/B 00/U 02/W 22/W
SHR 020/043 022/039 014/046 022/050 024/056 027/051 024/046
22/W 22/O 12/W 20/B 00/U 02/W 32/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 220347 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
847 PM MST SAT NOV 21 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
AN UPPER SHORT WAVE TROUGH AND ASSOCIATED COLD FRONT DROPPING
SOUTH OUT OF SOUTHERN SASKATCHEWAN HAVE MANAGED TO PRODUCE A FEW
SNOW SHOWERS IN DANIELS AND NORTHERN VALLEY COUNTIES EARLIER THIS
EVENING. THESE SHORT-LIVED SNOW SHOWERS WERE MANAGED WITH A NOW-
CAST SINCE THEY WERE EXPECTED TO DISSIPATE SOON AFTER CROSSING
THE BORDER. RADAR ECHOES HAVE FADED BY 8 PM SO WILL NOT ADD POPS
TO UPDATE. THE STRONG SURFACE PRESSURE GRADIENT REMAINS HOWEVER SO
WINDS HAVE BEEN SLOW IN DIMINISHING. THEREFORE ADJUSTED WIND
STRENGTH UP A BIT FOR THE REMAINDER OF THE NIGHT. SATELLITE IR
IMAGERY DISPLAYS MID TO HIGH CLOUDS UPSTREAM SO ALSO INCREASED SKY
COVER OVER THE EAST FOR AFTER MIDNIGHT. SCT
PREVIOUS DISCUSSION...
CURRENT GOES WATER VAPOR IMAGERY REVEALS A LONGWAVE TROUGH NOW IN
PLACE OVER THE WESTERN UNITED STATES. THE LEADING SHORTWAVE TROUGH
HAS NOW LIFTED OVER SASKATCHEWAN AND HAS DRUG A COLD FRONT THROUGH
NORTHEAST MONTANA INTO THE DAKOTAS. A TIGHT SURFACE PRESSURE
GRADIENT HAS DEVELOPED OVER NORTHEAST MONTANA IN THE WAKE OF THESE
FEATURES AND COMBINED WITH COLD AIR ADVECTION TO PRODUCE A STRONG
WEST WIND. A SECONDARY FRONTAL SYSTEM AND ASSOCIATED VORTICITY
MAXIMA IS CURRENTLY DROPPING SOUTHEAST OVER SOUTHEAST ALBERTA AND
SOUTHWEST SASKATCHEWAN. THE VERTICAL ASCENT ASSOCIATED WITH THIS
SYSTEM IS COMBINING WITH DIURNAL HEATING AND CREATING A FEW SNOW
SHOWERS IN CANADA. AS THESE SHOWERS MOVE SOUTH THEY ENCOUNTER A
VERY DRY AIRMASS AND HENCE AT THIS POINT IT APPEAR TO BE PRIMARILY
VIRGA ALONG THE WESTERN PORTION OF THE HI-LINE.
THIS SECONDARY FRONTAL SYSTEM WILL CROSS THE THE LOCAL AREA THIS
EVENING. THE SHOWERS SHOULD WEAKEN AND BEGIN TO DISSIPATE AFTER
SUNSET...BUT THERE MAY BE ENOUGH UPPER FORCING TO MAINTAIN A FEW
WEAK SHOWERS INTO THIS EVENING. THEREFORE...ISOLATED FLURRIES WERE
ADDED TO THE NORTHWEST ZONES THIS EVENING ALTHOUGH ITS MAIN
AFFECT WILL BE INCREASED CLOUD COVER ACROSS THE NORTH AND IT WILL
ALSO MAINTAIN THE WIND THROUGH THE EVENING. ALBEIT MUCH WEAKER AS
LOW-LEVEL LAPSE RATES LESSEN AFTER SUNSET...SO THE CURRENT TIMING
OF THE LAKE WIND ADVISORY SHOULD SUFFICE. SHORTWAVE RIDGING BEGINS
AFTER MIDNIGHT...SO CLOUD COVER SHOULD QUICKLY DECREASE ALONG WITH
THE WIND. MINIMUM TEMPERATURES WILL BE SEASONALLY COOL ACROSS
MOST OF THE REGION.
CLOUD COVER WILL BEGIN TO INCREASE SUNDAY AFTERNOON AS ANOTHER
SHORTWAVE TROUGH DIVES INTO THE PACIFIC NORTHWEST. THIS TROUGH
WILL TRAVERSE ACROSS THE LOCAL AREA SUNDAY NIGHT AND EARLY MONDAY.
THE UPPER DYNAMICS WITH THIS SYSTEM ARE DECENT...BUT THE LOWER
PORTION OF THE ATMOSPHERE WILL REMAIN DRY...SO IT WILL BE
DIFFICULT TO GET MUCH MOISTURE TO THE SURFACE. THEREFORE...ONLY
SLIGHT CHANCE POPS ARE FORECAST WITH PRECIPITATION TYPE AS LIGHT
SNOW. TEMPERATURES WILL BE COOLER SUNDAY AND MONDAY...BUT STILL
ABOVE SEASONAL AVERAGES. AJZ
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
GFS AND EC MODELS GENERALLY AGREE THROUGH FRIDAY. FORECAST IS
FAIRLY DRY FOR THE LONG TERM WITH A SERIES OF PASSING SHORTWAVE
TROUGHS AND RIDGES. OUTSIDE CHANCE FOR A RAIN OR SNOW SHOWER
TUESDAY OR TUESDAY NIGHT AS A SOMEWHAT DRY CLIPPER-LIKE SYSTEM
DROPS INTO THE CENTRAL US. MOST SIGNIFICANT FEATURE IN THE LONG
TERM IS RIDGING WEDNESDAY INTO THURSDAY...WHICH SHOULD GIVE CLEAR
WEATHER AND ABOVE NORMAL TEMPERATURES FOR THANKSGIVING DAY.
RIDGE BREAKS DOWN WITH A SHARPER TROUGH IN THE EC MODEL...WHICH
SUGGESTS A HIGHER CHANCE FOR SOME SNOW ON SATURDAY THAN SEEN IN
THE GFS. MARTIN
PREVIOUS LONG TERM DISCUSSION...SHORTWAVE TROUGH DROPS SOUTHEAST
OUT OF SASKATCHEWAN DURING THE DAY TUESDAY AND MAY BRING A SLIGHT
CHANCE OF RAIN OR SNOW. THIS FAST MOVING SYSTEM WILL HAVE LIMITED
MOISTURE WITH IT.
AN UPPER RIDGE BUILDS INTO THE AREA ON WEDNESDAY AND WILL BRING
WARM AND DRY WEATHER THROUGH THANKSGIVING DAY FOR SURE.
MODELS HAVE SOME DIFFERENCES ON TRACK OF A SHORTWAVE THAT MOVES
INLAND FROM THE PACIFIC ON FRIDAY. ECMWF TAKES THE SYSTEM SOUTH OF
THE AREA WHILE THE GFS BRINGS IT ACROSS MONTANA. EITHER WAY...A
COLD FRONT WILL AFFECT THE FORECAST AREA ON FRIDAY WITH COOLER
TEMPERATURES EXPECTED NEXT WEEKEND. WILL KEEP THE FORECAST DRY FOR
THE MOST PART FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. STRONG WEST WINDS THIS AFTERNOON SHOULD ABATE
AFTER SUNSET...DECREASING TO AROUND 10 KTS. WINDS TURN
SOUTHEASTERLY ON SUNDAY UP TO AROUND 15 KTS. MOSTLY CLEAR TO
SCATTERED SKIES ON SUNDAY WITH CEILINGS LOWERING OUT WEST SUNDAY
EVENING. MARTIN
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 220334
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
834 PM MST SAT NOV 21 2009
.UPDATE...
AN UPDATE FOR REMOVING SOME PRECIPITATION AREAS ACROSS NORTH
CENTRAL AND CENTRAL MONTANA. THE DISTURBANCE THAT MOVED THROUGH
NORTH CENTRAL MONTANA HAS TAKEN ITS PRECIP INTO NORTHEAST MONTANA.
PARTLY CLOUDY AND BREEZY CONDITIONS REMAIN. ALSO REDUCED PRECIP
CHANCES IN THE SOUTHWEST. AGAIN...THE AREA OF PRECIP HAS
DIMINISHED AND EXPECT THIS TREND TO CONTINUE INTO EARLY MORNING
HOURS. ALSO DROPPED TEMPS A BIT OVER CENTRAL MONTANA. CLEAR SKIES
AND DRY AIR IS DROPPING TEMPS INTO MID 20S. EXPECT WINDS TO
CONTINUE STRONG ENOUGH SO THAT MUCH MORE COOLING DOES NOT
OCCUR...BUT SUFFICIENT TO DROP THE TEMPS A BIT. NO OTHER CHANGES. DB
&&
.AVIATION...
UPDATED 0000Z.
A WEAK UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
EVENING...ALLOWING FOR GENERALLY CLEAR/PARTLY CLOUDY SKIES OVER THE
REGION. THE NEXT PACIFIC STORM WILL MOVE INTO THE ROCKY MOUNTAIN
FRONT AND SOUTHWEST MONTANA AFTER 17Z SUNDAY...AND THEN CONTINUE TO
AFFECT THE REGION THROUGH SUNDAY EVENING. VFR CONDITIONS ARE
EXPECTED ON SUNDAY MORNING...HOWEVER...THEY WILL GRADUALLY LOWER TO
IFR/LIFR CONDITIONS OVER THE REGION DURING THE EARLY AFTERNOON HOURS
ON SUNDAY. EXPECT MOUNTAINS TO BE OBSCURED AFTER 16Z SUNDAY. BRUSDA
&&
.PREV DISCUSSION...
/ISSUED 500 PM MST SAT NOV 21 2009/
THE UPPER LEVEL TROUGH THAT MOVED THROUGH HE REGION EARLIER TODAY
WILL EXIT IT THE REGION TONIGHT FOLLOWED BY A BRIEF PERIOD OF
DRYING UNDER WEAK UPPER LEVEL RIDGING. WIDELY SCATTERED SNOW
SHOWERS OVER THE MTNS WILL DIMINISH EARLY THIS EVENING WITH A FEW
ISOLATED SNOW SHOWERS POSSIBLE THROUGH EARLY THIS EVENING AS WELL
ALONG THE CANADIAN BORDER IN ASSOCIATION WITH A WEAK DISTURBANCE
MOVING SOUTHEAST FROM ALBERTA. CLOUDS AND MOISTURE WILL INCREASE
AGAIN ON SUNDAY AS A VIGOROUS PACIFIC STORM SYSTEM MOVES ONSHORE
AND QUICKLY MOVES TO THE NORTHERN ROCKIES BY SUNDAY EVENING AND
ACROSS THE STATE SUNDAY NIGHT. THIS SYSTEM WILL BRING ANOTHER
PERIOD OF SNOW TO THE MOUNTAINS SUNDAY AFTERNOON AND EVENING WITH
SNOW SHOWERS POSSIBLE ELSEWHERE. MOIST AND UNSTABLE WEST TO
NORTHWEST FLOW WILL MAINTAIN AT LEAST A CHANCE OF SNOW SHOWERS OVER
THE CENTRAL AND SW MT MTNS THROUGH SUNDAY NIGHT. ACCUMULATIONS OF AN
INCH OR LESS ARE EXPECTED ACROSS THE VALLEYS OF SW MT WITH 1 TO 3
INCHES POSSIBLE IN THE MTNS. THE MOST PERSISTENT SNOW WILL OCCUR
OVER THE GALLATIN AND MADISON MTN RANGES WHERE HIGHER AMOUNTS OF 3
TO 5 INCHES APPEAR LIKELY FOR ELEVATIONS ABOVE 6000 FT THROUGH
SUNDAY NIGHT. UPPER LEVEL RIDGING BUILDS IN BEHIND THIS SYSTEM ON
MONDAY FOR DRIER CONDITIONS. TEMPERATURES WILL REMAIN SEASONABLY
COOL THROUGH MONDAY WITH CLEARING SKIES TONIGHT ALLOWING TEMPS TO
DROP INTO THE SINGLE DIGITS OR LOWER IN SOME OF THE SW MT VALLEYS.
HOENISCH
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 22 38 29 42 / 0 20 20 0
CTB 22 36 28 40 / 0 20 20 0
HLN 22 38 28 39 / 0 40 30 10
BZN 9 36 17 35 / 0 60 40 10
WEY 3 27 11 26 / 30 90 80 20
DLN 13 31 16 30 / 0 60 40 0
HVR 19 41 25 45 / 20 20 10 10
LWT 19 37 22 38 / 0 40 40 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 220002 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
502 PM MST SAT NOV 21 2009
UPDATED TO EXPIRE LAKE WIND ADVISORY
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
CURRENT GOES WATER VAPOR IMAGERY REVEALS A LONGWAVE TROUGH NOW IN
PLACE OVER THE WESTERN UNITED STATES. THE LEADING SHORTWAVE TROUGH
HAS NOW LIFTED OVER SASKATCHEWAN AND HAS DRUG A COLD FRONT THROUGH
NORTHEAST MONTANA INTO THE DAKOTAS. A TIGHT SURFACE PRESSURE
GRADIENT HAS DEVELOPED OVER NORTHEAST MONTANA IN THE WAKE OF THESE
FEATURES AND COMBINED WITH COLD AIR ADVECTION TO PRODUCE A STRONG
WEST WIND. A SECONDARY FRONTAL SYSTEM AND ASSOCIATED VORTICITY
MAXIMA IS CURRENTLY DROPPING SOUTHEAST OVER SOUTHEAST ALBERTA AND
SOUTHWEST SASKATCHEWAN. THE VERTICAL ASCENT ASSOCIATED WITH THIS
SYSTEM IS COMBINING WITH DIURNAL HEATING AND CREATING A FEW SNOW
SHOWERS IN CANADA. AS THESE SHOWERS MOVE SOUTH THEY ENCOUNTER A
VERY DRY AIRMASS AND HENCE AT THIS POINT IT APPEAR TO BE PRIMARILY
VIRGA ALONG THE WESTERN PORTION OF THE HI-LINE.
THIS SECONDARY FRONTAL SYSTEM WILL CROSS THE THE LOCAL AREA THIS
EVENING. THE SHOWERS SHOULD WEAKEN AND BEGIN TO DISSIPATE AFTER
SUNSET...BUT THERE MAY BE ENOUGH UPPER FORCING TO MAINTAIN A FEW
WEAK SHOWERS INTO THIS EVENING. THEREFORE...ISOLATED FLURRIES WERE
ADDED TO THE NORTHWEST ZONES THIS EVENING ALTHOUGH ITS MAIN
AFFECT WILL BE INCREASED CLOUD COVER ACROSS THE NORTH AND IT WILL
ALSO MAINTAIN THE WIND THROUGH THE EVENING. ALBEIT MUCH WEAKER AS
LOW-LEVEL LAPSE RATES LESSEN AFTER SUNSET...SO THE CURRENT TIMING
OF THE LAKE WIND ADVISORY SHOULD SUFFICE. SHORTWAVE RIDGING BEGINS
AFTER MIDNIGHT...SO CLOUD COVER SHOULD QUICKLY DECREASE ALONG WITH
THE WIND. MINIMUM TEMPERATURES WILL BE SEASONALLY COOL ACROSS
MOST OF THE REGION.
CLOUD COVER WILL BEGIN TO INCREASE SUNDAY AFTERNOON AS ANOTHER
SHORTWAVE TROUGH DIVES INTO THE PACIFIC NORTHWEST. THIS TROUGH
WILL TRAVERSE ACROSS THE LOCAL AREA SUNDAY NIGHT AND EARLY MONDAY.
THE UPPER DYNAMICS WITH THIS SYSTEM ARE DECENT...BUT THE LOWER
PORTION OF THE ATMOSPHERE WILL REMAIN DRY...SO IT WILL BE
DIFFICULT TO GET MUCH MOISTURE TO THE SURFACE. THEREFORE...ONLY
SLIGHT CHANCE POPS ARE FORECAST WITH PRECIPITATION TYPE AS LIGHT
SNOW. TEMPERATURES WILL BE COOLER SUNDAY AND MONDAY...BUT STILL
ABOVE SEASONAL AVERAGES. AJZ
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
GFS AND EC MODELS GENERALLY AGREE THROUGH FRIDAY. FORECAST IS
FAIRLY DRY FOR THE LONG TERM WITH A SERIES OF PASSING SHORTWAVE
TROUGHS AND RIDGES. OUTSIDE CHANCE FOR A RAIN OR SNOW SHOWER
TUESDAY OR TUESDAY NIGHT AS A SOMEWHAT DRY CLIPPER-LIKE SYSTEM
DROPS INTO THE CENTRAL US. MOST SIGNIFICANT FEATURE IN THE LONG
TERM IS RIDGING WEDNESDAY INTO THURSDAY...WHICH SHOULD GIVE CLEAR
WEATHER AND ABOVE NORMAL TEMPERATURES FOR THANKSGIVING DAY.
RIDGE BREAKS DOWN WITH A SHARPER TROUGH IN THE EC MODEL...WHICH
SUGGESTS A HIGHER CHANCE FOR SOME SNOW ON SATURDAY THAN SEEN IN
THE GFS. MARTIN
PREVIOUS LONG TERM DISCUSSION...SHORTWAVE TROUGH DROPS SOUTHEAST
OUT OF SASKATCHEWAN DURING THE DAY TUESDAY AND MAY BRING A SLIGHT
CHANCE OF RAIN OR SNOW. THIS FAST MOVING SYSTEM WILL HAVE LIMITED
MOISTURE WITH IT.
AN UPPER RIDGE BUILDS INTO THE AREA ON WEDNESDAY AND WILL BRING
WARM AND DRY WEATHER THROUGH THANKSGIVING DAY FOR SURE.
MODELS HAVE SOME DIFFERENCES ON TRACK OF A SHORTWAVE THAT MOVES
INLAND FROM THE PACIFIC ON FRIDAY. ECMWF TAKES THE SYSTEM SOUTH OF
THE AREA WHILE THE GFS BRINGS IT ACROSS MONTANA. EITHER WAY...A
COLD FRONT WILL AFFECT THE FORECAST AREA ON FRIDAY WITH COOLER
TEMPERATURES EXPECTED NEXT WEEKEND. WILL KEEP THE FORECAST DRY FOR
THE MOST PART FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. STRONG WEST WINDS THIS AFTERNOON SHOULD ABATE
AFTER SUNSET...DECREASING TO AROUND 10 KTS. WINDS TURN
SOUTHEASTERLY ON SUNDAY UP TO AROUND 15 KTS. MOSTLY CLEAR TO
SCATTERED SKIES ON SUNDAY WITH CEILINGS LOWERING OUT WEST SUNDAY
EVENING. MARTIN
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 212350
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
500 PM MST SAT NOV 21 2009
UPDATED AVIATION SECTION
.DISCUSSION...
THE UPPER LEVEL TROUGH THAT MOVED THROUGH HE REGION EARLIER TODAY
WILL EXIT IT THE REGION TONIGHT FOLLOWED BY A BRIEF PERIOD OF
DRYING UNDER WEAK UPPER LEVEL RIDGING. WIDELY SCATTERED SNOW
SHOWERS OVER THE MTNS WILL DIMINISH EARLY THIS EVENING WITH A FEW
ISOLATED SNOW SHOWERS POSSIBLE THROUGH EARLY THIS EVENING AS WELL
ALONG THE CANADIAN BORDER IN ASSOCIATION WITH A WEAK DISTURBANCE
MOVING SOUTHEAST FROM ALBERTA. CLOUDS AND MOISTURE WILL INCREASE
AGAIN ON SUNDAY AS A VIGOROUS PACIFIC STORM SYSTEM MOVES ONSHORE
AND QUICKLY MOVES TO THE NORTHERN ROCKIES BY SUNDAY EVENING AND
ACROSS THE STATE SUNDAY NIGHT. THIS SYSTEM WILL BRING ANOTHER
PERIOD OF SNOW TO THE MOUNTAINS SUNDAY AFTERNOON AND EVENING WITH
SNOW SHOWERS POSSIBLE ELSEWHERE. MOIST AND UNSTABLE WEST TO
NORTHWEST FLOW WILL MAINTAIN AT LEAST A CHANCE OF SNOW SHOWERS OVER
THE CENTRAL AND SW MT MTNS THROUGH SUNDAY NIGHT. ACCUMULATIONS OF AN
INCH OR LESS ARE EXPECTED ACROSS THE VALLEYS OF SW MT WITH 1 TO 3
INCHES POSSIBLE IN THE MTNS. THE MOST PERSISTENT SNOW WILL OCCUR
OVER THE GALLATIN AND MADISON MTN RANGES WHERE HIGHER AMOUNTS OF 3
TO 5 INCHES APPEAR LIKELY FOR ELEVATIONS ABOVE 6000 FT THROUGH
SUNDAY NIGHT. UPPER LEVEL RIDGING BUILDS IN BEHIND THIS SYSTEM ON
MONDAY FOR DRIER CONDITIONS. TEMPERATURES WILL REMAIN SEASONABLY
COOL THROUGH MONDAY WITH CLEARING SKIES TONIGHT ALLOWING TEMPS TO
DROP INTO THE SINGLE DIGITS OR LOWER IN SOME OF THE SW MT VALLEYS.
HOENISCH
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.AVIATION...
UPDATED 0000Z.
A WEAK UPPER LEVEL RIDGE WILL BUILD OVER THE REGION THIS
EVENING...ALLOWING FOR GENERALLY CLEAR/PARTLY CLOUDY SKIES OVER THE
REGION. THE NEXT PACIFIC STORM WILL MOVE INTO THE ROCKY MOUNTAIN
FRONT AND SOUTHWEST MONTANA AFTER 17Z SUNDAY...AND THEN CONTINUE TO
AFFECT THE REGION THROUGH SUNDAY EVENING. VFR CONDITIONS ARE
EXPECTED ON SUNDAY MORNING...HOWEVER...THEY WILL GRADUALLY LOWER TO
IFR/LIFR CONDITIONS OVER THE REGION DURING THE EARLY AFTERNOON HOURS
ON SUNDAY. EXPECT MOUNTAINS TO BE OBSCURED AFTER 16Z SUNDAY. BRUSDA
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 24 38 29 42 / 0 20 20 0
CTB 22 36 28 40 / 0 20 20 0
HLN 22 38 28 39 / 0 40 30 10
BZN 9 36 17 35 / 0 60 40 10
WEY 3 27 11 26 / 30 90 80 20
DLN 13 31 16 30 / 0 60 40 0
HVR 19 41 25 45 / 20 20 10 10
LWT 19 37 22 38 / 0 40 40 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...COULSTON
AVIATION...BRUSDA
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 212151
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
251 PM MST SAT NOV 21 2009
.DISCUSSION...
THE UPPER LEVEL TROUGH THAT MOVED THROUGH HE REGION EARLIER TODAY
WILL EXIT IT THE REGION TONIGHT FOLLOWED BY A BRIEF PERIOD OF
DRYING UNDER WEAK UPPER LEVEL RIDGING. WIDELY SCATTERED SNOW
SHOWERS OVER THE MTNS WILL DIMINISH EARLY THIS EVENING WITH A FEW
ISOLATED SNOW SHOWERS POSSIBLE THROUGH EARLY THIS EVENING AS WELL
ALONG THE CANADIAN BORDER IN ASSOCIATION WITH A WEAK DISTURBANCE
MOVING SOUTHEAST FROM ALBERTA. CLOUDS AND MOISTURE WILL INCREASE
AGAIN ON SUNDAY AS A VIGOROUS PACIFIC STORM SYSTEM MOVES ONSHORE
AND QUICKLY MOVES TO THE NORTHERN ROCKIES BY SUNDAY EVENING AND
ACROSS THE STATE SUNDAY NIGHT. THIS SYSTEM WILL BRING ANOTHER
PERIOD OF SNOW TO THE MOUNTAINS SUNDAY AFTERNOON AND EVENING WITH
SNOW SHOWERS POSSIBLE ELSEWHERE. MOIST AND UNSTABLE WEST TO
NORTHWEST FLOW WILL MAINTAIN AT LEAST A CHANCE OS SNOW SHOWERS
OVER THE CENTRAL AND SW MT MTNS THROUGH SUNDAY NIGHT.
ACCUMULATIONS OF AN INCH OR LESS ARE EXPECTED ACROSS THE VALLEYS
OF SW MT WITH 1 TO 3 INCHES POSSIBLE IN THE MTNS. THE MOST
PERSISTENT SNOW WILL OCCUR OVER THE GALLATIN AND MADISON MTN
RANGES WHERE HIGHER AMOUNTS OF 3 TO 5 INCHES APPEAR LIKELY FOR
ELEVATIONS ABOVE 6000 FT THROUGH SUNDAY NIGHT. UPPER LEVEL RIDGING
BUILDS IN BEHIND THIS SYSTEM ON MONDAY FOR DRIER CONDITIONS.
TEMPERATURES WILL REMAIN SEASONABLY COOL THROUGH MONDAY WITH
CLEARING SKIES TONIGHT ALLOWING TEMPS TO DROP INTO THE SINGLE
DIGITS OR LOWER IN SOME OF THE SW MT VALLEYS. HOENISCH
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.AVIATION...
UPDATED 1740Z.
AN UPPER LEVEL LOW PRESSURE TROUGH WILL CONTINUE TO MAKE ITS WAY
ACROSS CENTRAL MT THIS AFTN/EVE. MOST OF ASSOCIATED MOISTURE HAS
ALREADY PUSHED TOWARD KBIL BUT LOCATIONS WEST OF A KBIL-TO-KHLN LINE
WILL SEE A FEW RESIDUAL SNOWSHOWERS THROUGH MID-AFTN. CEILINGS
SHOULD REMAIN VFR ACROSS THE REGION...THOUGH HIGHER TERRAIN WILL BE
OBSCURED WITH MVFR/IFR CONDITIONS NEAR ANY PRECIPITATION AREAS.
WINDS WILL BE GUSTY OVER THE PLAINS AND ROCKY MTN FRONT THIS AFTN
WITH WIDESPREAD GUSTS OF 25 TO 35 KTS...AND SOME LOCATIONS FROM
GLACIER NP TO KHVR SEEING GUSTS OF 40 TO 50 KTS. AS THE TROUGH
MOVES FURTHER EAST THIS EVE...WINDS SHOULD DECREASE TOWARD SUNSET
AND SKIES WILL BE MOSTLY CLEAR OVERNIGHT AT ALL TERMINALS.
WARANAUSKAS
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 24 38 29 42 / 0 20 20 0
CTB 22 36 28 40 / 0 20 20 0
HLN 22 38 28 39 / 0 40 30 10
BZN 9 36 17 35 / 0 60 40 10
WEY 3 27 11 26 / 30 90 80 20
DLN 13 31 16 30 / 0 60 40 0
HVR 19 41 25 45 / 20 20 10 10
LWT 19 37 22 38 / 0 40 40 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...COULSTON
AVIATION...WARANAUSKAS
WEATHER.GOV/GREATFALLS
000
FXUS65 KMSO 212146
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
246 PM MST SAT NOV 21 2009
.DISCUSSION...SHOWER ACTIVITY IS EXPECTED TO WANE THIS EVENING AS
A SHORTWAVE RIDGE BUILDS AHEAD OF AN APPROACHING UPPER LEVEL
TROUGH. THIS WILL ALLOW SKIES TO CLEAR ENOUGH TO SEE A QUICK DROP
IN TEMPERATURES AFTER SUNSET AND THE POTENTIAL FOR SOME VALLEY FOG
FORMATION...MAINLY IN NORTH CENTRAL IDAHO VALLEYS.
THE UPPER LEVEL TROUGH IS EXPECTED TO BEGIN TO MOVE THROUGH THE
NORTHERN ROCKIES DURING THE DAY SUNDAY. THIS FEATURE WILL BE
ACCOMPANIED WITH A STRONG UPPER LEVEL JET AND SURFACE COLD
FRONT...WHICH WILL COMBINE WITH ABUNDANT MOISTURE TO PRODUCE
WIDESPREAD PRECIPITATION OVER MOST ALL OF WESTERN MONTANA AND
NORTH CENTRAL IDAHO. TEMPERATURES ARE EXPECTED TO REMAIN COOL
ENOUGH THAT ALL BUT THE LOWEST VALLEYS (BELOW 2500 FEET) SHOULD
SEE PRECIPITATION FALL AS SNOW. THE MOST FAVORABLE DYNAMICS WITH THIS
SYSTEM WILL BE FOCUSED OVER NORTH CENTRAL IDAHO HOWEVER...AND THUS
THE BEST SNOW PRODUCTION IS EXPECTED OVER THE CLEARWATER AND
BITTERROOT MOUNTAINS. IN ADDITION TO EXPECTED ACCUMULATING
SNOW IN THESE AREAS...GUSTY SOUTHWEST TO WEST WINDS WILL CREATE LOWERED
VISIBILITY AND HAZARDOUS DRIVING CONDITIONS OVER PORTIONS OF
NORTHCENTRAL IDAHO AND WESTERN MONTANA. A WINTER WEATHER ADVISORY
HAS BEEN ISSUED...PLEASE SEE WWW.WEATHER.GOV/MISSOULA FOR FURTHER
DETAILS. THE UPPER LEVEL TROUGH WILL MOVE EASTWARD OVERNIGHT
SUNDAY...BRINGING A NORTHWESTERLY FLOW OVER THE REGION. WHILE THE
HEAVIEST PRECIPITATION SHOULD COME TO AN END...THERE IS THE
POSSIBILITY OF BANDED PRECIPITATION DEVELOPING IN TO MONDAY.
TUESDAY THROUGH SUNDAY...A SHORTWAVE TROUGH WILL PASS TO THE NORTH
ALONG THE MONTANA CANADIAN BORDER ON TUESDAY BRINGING A CHANCE FOR
PRECIPITATION IN NORTHWEST MONTANA BEFORE A HIGH PRESSURE RIDGE
BEGINS TO OVERTAKE THE REGION. THIS HIGH PRESSURE HAS BEEN SHOWING
SIMILAR TIMING AND SLIGHTLY DIFFERENT AMPLITUDES BETWEEN THE ECMWF
AND THE GFS. THE AMPLIFYING RIDGE WILL POSE A THREAT OF WIDESPREAD
VALLEY FOG STARTING WEDNESDAY MORNING. MODEL PLAN VIEWS AND CROSS
SECTIONS SHOW ENERGY PASSING THROUGH THE RIDGE WEDNESDAY MORNING...
WHICH COULD INHIBIT VALLEY INVERSION DEVELOPMENT...HOWEVER...MODEL
SOUNDING FOR THE SAME TIME FRAME DO SHOW INVERSIONS
INITIATING...SO WILL KEEP THE MENTION OF FOG IN THE FORECAST. HIGH
PRESSURE LOOKS TO LINGER INTO THURSDAY WITH DRIER...SUBSIDING AIR
AND STRONG INVERSIONS FORECAST BY MODEL SOUNDINGS. THIS IS
SOMEWHAT DIFFERENT FROM YESTERDAY...BUT THESE FEATURES WOULD
PROMOTE FOG ON THURSDAY. WILL CONTINUE TO MONITOR FOG POTENTIAL
ESPECIALLY FOR THE GLACIER PARK INTERNATIONAL AIRPORT AND THE
MISSOULA AIRPORT AS HOLIDAY AIRLINE TRAVEL MAY BECOME ADVERSELY EFFECTED.
&&
.AVIATION...STRONG WEST-SOUTHWEST SURFACE WINDS WILL CONTINUE THROUGH
EARLY SATURDAY EVENING AND CLOUDS WILL BE ON THE INCREASE AS THE
NEXT PACIFIC WEATHER SYSTEM PUSHES INTO THE NORTHERN ROCKIES. SNOW
SHOWERS WILL START TO SPREAD ACROSS THE IDAHO PANHANDLE AND
NORTHWEST MONTANA SUNDAY MORNING...MOSTLY AFTER 22/1200Z. THE
REMAINDER OF WESTERN MONTANA AND NORTH CENTRAL IDAHO WILL SEE
SHOWERS SPREAD AREAWIDE LATER MIDDAY SUNDAY. SIGNIFICANTLY
LOWERED CEILINGS AND REDUCTIONS IN VISIBILITY WILL BE POSSIBLE
WITH HEAVIER SNOW SHOWERS AT THE TERMINALS. SURFACE WINDS WILL
REMAIN BREEZY... BUT TO A LESSER DEGREE THAN WINDS OBSERVED ON
SATURDAY. OBSCURATIONS OF MOUNTAINS AND PASSES CAN BE EXPECTED.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 8 AM TO 11 PM MST SUNDAY FOR
LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY FROM 8 AM TO 11 PM MST SUNDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER WEATHER ADVISORY FROM 7 AM TO 10 PM PST SUNDAY FOR
OROFINO/GRANGEVILLE REGION.
WINTER WEATHER ADVISORY FROM 7 AM TO 10 PM PST SUNDAY FOR
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...PALLISTER
LONG TERM....KITSMILLER
AVIATION...NOLTE
000
FXUS65 KBYZ 212145
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
245 PM MST SAT NOV 21 2009
.SHORT TERM...VALID FOR SUN AND MON...
AIRMASS FAIRLY DRY IN A POST FRONTAL ENVIRONMENT WITH GUSTY
NORTHWEST WINDS PERSISTING OVER THE EASTERN ZONES. UPPER LEVEL
TROUGH OVER THE AREA WILL BEGIN YIELDING TO A SHORTWAVE RIDGE
TONIGHT INDUCED BY A MUCH STRONGER SYSTEM PUSHING INTO THE PACIFIC
NORTHWEST. AREAS OF PRECIP LINGERING SOUTH WEST OF KBIL AND THINK
THAT AS THIS ACTIVITY SHIFTS EASTWARD IT WILL PERSIST SINCE IT
WILL BE SHIFTING AWAY FROM DOWNSLOPE INFLUENCES. THIS ACTIVITY
SHOULD CLEAR AFTER MIDNIGHT AND WILL HAVE A CHANCE FOR
TEMPERATURES TO FALL SHARPLY WITH CLEARING SKIES AND LOW DEWPOINTS.
HOWEVER...BY MORNING PRESSURE FALLS BEGIN QUICKLY ALONG THE
NORTHERN ROCKY FRONT AS THE NEXT WAVE MOVES EASTWARD ACROSS
WASHINGTON. A BRIEF PERIOD OF GAP FLOW WINDS WILL DEVELOP LATE
TONIGHT AND EARLY SUNDAY WITH STRONG SURFACE HIGH PRESSURE OVER
SOUTHEAST IDAHO WAITING FOR THE LEESIDE TROUGH TO FORM. THIS
SYSTEM IS EXPECTED TO FILL AS IT MOVES EASTWARD BUT IS STILL
PRETTY STRONG SO EXPECT AN INCREASE IN MOUNTAIN PRECIPITATION AND
HAVE ACCUMULATIONS MENTIONED BUT THINK THAT LOW LEVEL AIRMASS
OVER THE PLAINS WILL BE FAIRLY DRY AND PRECIP WILL HAVE A HARD
TIME REACHING THE GROUND. COLDER HEIGHTS ALOFT WILL KEEP
TEMPERATURES COOLER THAN TODAY BUT CLOSE TO 40 DEGREES IS
SEASONABLE FOR THIS TIME OF YEAR. GRADIENTS FOR WINDS WEAKEN A BIT
ON SUNDAY BUT AIRMASS WILL BE UNSTABLE AND MOMENTUM ALOFT WILL
HAVE AN EASY TIME MIXING DOWN. UPPER LOW FILLS AS IT GOES FROM
NORTHWEST MONTANA TO SOUTHEAST MONTANA SUNDAY NIGHT AND WHILE
AIRMASS IS STILL PRETTY DRY...CANNOT RULE SOME ISOLATED SHOWERS
BEING SQUEEZED OUT OF THE AIRMASS...ESPECIALLY OVER SOUTHEAST
MONTANA CLOSER TO THE COLDEST AIR ALOFT. HEIGHTS BEGIN TO BUILD
FROM WEST TO EAST ON MONDAY PUSHING ISOLATED SHOWERS INTO THE
DAKOTAS AND BRINGING CLEARING TO THE WESTERN ZONES. PRESSURE
GRADIENTS FOR GAP FLOW WINDS BEGIN TO TAKE SHAPE ON MONDAY NIGHT
AND HAVE BEGIN TO RAMP UP SPEEDS. OTHERWISE LOOKS DRY WITH CLEAR
SKIES AND LOW DEWPOINTS AGAIN SUPPORTING A COOL NIGHT. BORSUM
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
JUST SOME MINOR CHANGES MADE TO THE EXTENDED FORECAST THIS
AFTERNOON. UPPER LEVEL RIDGE WILL BE OVER THE FORECAST TUESDAY
MORNING AND HAVE DRIED OUT MOST PERIODS FOR THIS PERIOD. UPPER
LEVEL TROUGH SLIDES INTO NORTH DAKOTA TUESDAY AFTERNOON AND
TUESDAY NIGHT WITH SOME WEAK ENERGY MOVING INTO THE FORECAST AREA
AT THIS TIME. MODELS DO HINT AT A LITTLE PRECIP FOR THIS WEAK
SYSTEM SO HAVE SPREAD THE LOW POPS A LITTLE FARTHER WEST. DID ADD
POPS FOR THE CENTRAL AND WESTERN ZONES AS WELL FOR TUESDAY NIGHT.
THIS SYSTEM QUICKLY EXITS BY WEDNESDAY MORNING LEAVING DRY
CONDITIONS AND WARMER TEMPS THROUGH MUCH OF FRIDAY. MODELS BRING
IN THE NEXT SYSTEM ACROSS SOUTHERN CANADA ON FRIDAY NIGHT AND
SATURDAY WHERE THE ECMWF BRINGS THE SYSTEM RIGHT OVER THE
FORECAST AREAS. HAVE KEPT IN LOW POPS FOR MOST AREAS FOR NOW
UNTIL THE MODELS COME INTO BETTER AGREEMENT. SOLUM
&&
.AVIATION...
GUSTY WINDS UP TO 30 KNOTS WILL CONTINUE ACROSS THE AREA THROUGH
EARLY EVENING BEFORE TAPERING OFF. MVFR CONDITIONS AND MOUNTAIN
OBSCURATIONS WILL CONTINUE TO BE POSSIBLE THROUGH EARLY EVENING
BEFORE BECOMING DRY OVERNIGHT AS SOME ISOLATED RAIN AND SNOW
SHOWERS CONTINUE TO MOVE THROUGH. SOLUM
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 021/040 028/042 024/046 029/051 031/055 034/051 033/044
02/J 21/B 12/W 20/B 00/U 02/W 22/W
LVM 018/036 023/035 018/043 027/050 030/054 030/046 030/044
04/J 32/S 12/W 20/B 00/U 03/W 32/W
HDN 022/043 024/044 019/047 025/052 028/057 029/053 027/049
02/W 22/O 12/W 20/B 00/U 02/W 22/W
MLS 021/045 024/043 020/047 023/046 026/056 030/051 031/042
01/B 22/O 22/W 00/B 00/U 02/W 22/W
4BQ 020/042 021/042 019/045 022/046 025/056 028/051 028/044
21/N 23/O 12/W 20/B 00/U 02/W 22/W
BHK 020/045 021/040 019/043 023/040 025/054 026/051 028/043
11/B 22/O 22/W 00/B 00/U 02/W 22/W
SHR 019/043 022/039 014/046 022/050 024/056 027/051 024/046
22/W 22/O 12/W 20/B 00/U 02/W 32/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 212140
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
240 PM MST SAT NOV 21 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
CURRENT GOES WATER VAPOR IMAGERY REVEALS A LONGWAVE TROUGH NOW IN
PLACE OVER THE WESTERN UNITED STATES. THE LEADING SHORTWAVE TROUGH
HAS NOW LIFTED OVER SASKATCHEWAN AND HAS DRUG A COLD FRONT THROUGH
NORTHEAST MONTANA INTO THE DAKOTAS. A TIGHT SURFACE PRESSURE
GRADIENT HAS DEVELOPED OVER NORTHEAST MONTANA IN THE WAKE OF THESE
FEATURES AND COMBINED WITH COLD AIR ADVECTION TO PRODUCE A STRONG
WEST WIND. A SECONDARY FRONTAL SYSTEM AND ASSOCIATED VORTICITY
MAXIMA IS CURRENTLY DROPPING SOUTHEAST OVER SOUTHEAST ALBERTA AND
SOUTHWEST SASKATCHEWAN. THE VERTICAL ASCENT ASSOCIATED WITH THIS
SYSTEM IS COMBINING WITH DIURNAL HEATING AND CREATING A FEW SNOW
SHOWERS IN CANADA. AS THESE SHOWERS MOVE SOUTH THEY ENCOUNTER A
VERY DRY AIRMASS AND HENCE AT THIS POINT IT APPEAR TO BE PRIMARILY
VIRGA ALONG THE WESTERN PORTION OF THE HI-LINE.
THIS SECONDARY FRONTAL SYSTEM WILL CROSS THE THE LOCAL AREA THIS
EVENING. THE SHOWERS SHOULD WEAKEN AND BEGIN TO DISSIPATE AFTER
SUNSET...BUT THERE MAY BE ENOUGH UPPER FORCING TO MAINTAIN A FEW
WEAK SHOWERS INTO THIS EVENING. THEREFORE...ISOLATED FLURRIES WERE
ADDED TO THE NORTHWEST ZONES THIS EVENING ALTHOUGH ITS MAIN
AFFECT WILL BE INCREASED CLOUD COVER ACROSS THE NORTH AND IT WILL
ALSO MAINTAIN THE WIND THROUGH THE EVENING. ALBEIT MUCH WEAKER AS
LOW-LEVEL LAPSE RATES LESSEN AFTER SUNSET...SO THE CURRENT TIMING
OF THE LAKE WIND ADVISORY SHOULD SUFFICE. SHORTWAVE RIDGING BEGINS
AFTER MIDNIGHT...SO CLOUD COVER SHOULD QUICKLY DECREASE ALONG WITH
THE WIND. MINIMUM TEMPERATURES WILL BE SEASONALLY COOL ACROSS
MOST OF THE REGION.
CLOUD COVER WILL BEGIN TO INCREASE SUNDAY AFTERNOON AS ANOTHER
SHORTWAVE TROUGH DIVES INTO THE PACIFIC NORTHWEST. THIS TROUGH
WILL TRAVERSE ACROSS THE LOCAL AREA SUNDAY NIGHT AND EARLY MONDAY.
THE UPPER DYNAMICS WITH THIS SYSTEM ARE DECENT...BUT THE LOWER
PORTION OF THE ATMOSPHERE WILL REMAIN DRY...SO IT WILL BE
DIFFICULT TO GET MUCH MOISTURE TO THE SURFACE. THEREFORE...ONLY
SLIGHT CHANCE POPS ARE FORECAST WITH PRECIPITATION TYPE AS LIGHT
SNOW. TEMPERATURES WILL BE COOLER SUNDAY AND MONDAY...BUT STILL
ABOVE SEASONAL AVERAGES. AJZ
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
GFS AND EC MODELS GENERALLY AGREE THROUGH FRIDAY. FORECAST IS
FAIRLY DRY FOR THE LONG TERM WITH A SERIES OF PASSING SHORTWAVE
TROUGHS AND RIDGES. OUTSIDE CHANCE FOR A RAIN OR SNOW SHOWER
TUESDAY OR TUESDAY NIGHT AS A SOMEWHAT DRY CLIPPER-LIKE SYSTEM
DROPS INTO THE CENTRAL US. MOST SIGNIFICANT FEATURE IN THE LONG
TERM IS RIDGING WEDNESDAY INTO THURSDAY...WHICH SHOULD GIVE CLEAR
WEATHER AND ABOVE NORMAL TEMPERATURES FOR THANKSGIVING DAY.
RIDGE BREAKS DOWN WITH A SHARPER TROUGH IN THE EC MODEL...WHICH
SUGGESTS A HIGHER CHANCE FOR SOME SNOW ON SATURDAY THAN SEEN IN
THE GFS. MARTIN
PREVIOUS LONG TERM DISCUSSION...SHORTWAVE TROUGH DROPS SOUTHEAST
OUT OF SASKATCHEWAN DURING THE DAY TUESDAY AND MAY BRING A SLIGHT
CHANCE OF RAIN OR SNOW. THIS FAST MOVING SYSTEM WILL HAVE LIMITED
MOISTURE WITH IT.
AN UPPER RIDGE BUILDS INTO THE AREA ON WEDNESDAY AND WILL BRING
WARM AND DRY WEATHER THROUGH THANKSGIVING DAY FOR SURE.
MODELS HAVE SOME DIFFERENCES ON TRACK OF A SHORTWAVE THAT MOVES
INLAND FROM THE PACIFIC ON FRIDAY. ECMWF TAKES THE SYSTEM SOUTH OF
THE AREA WHILE THE GFS BRINGS IT ACROSS MONTANA. EITHER WAY...A
COLD FRONT WILL AFFECT THE FORECAST AREA ON FRIDAY WITH COOLER
TEMPERATURES EXPECTED NEXT WEEKEND. WILL KEEP THE FORECAST DRY FOR
THE MOST PART FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. STRONG WEST WINDS THIS AFTERNOON SHOULD ABATE
AFTER SUNSET...DECREASING TO AROUND 10 KTS. WINDS TURN
SOUTHEASTERLY ON SUNDAY UP TO AROUND 15 KTS. MOSTLY CLEAR TO
SCATTERED SKIES ON SUNDAY WITH CEILINGS LOWERING OUT WEST SUNDAY
EVENING. MARTIN
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR FORT PECK
LAKE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 211751
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1040 AM MST SAT NOV 21 2009
AVIATION SECTION UPDATED
.UPDATE...
UPPER LEVEL TROUGH IS PROGRESSING ACROSS THE REGION THIS MORNING
WHILE THE ASSOCIATED PACIFIC COLD FRONT HAS MOVED THROUGH ALL ZONES
AND WILL CONTINUE TO PROGRESS EAST INTO THE DAKOTAS BY THIS
AFTERNOON. A PERIOD OF SNOW OCCURRED WITH THE FRONTAL PASSAGE
ACROSS MUCH OF SW MT EARLY THIS MORNING...WITH ONLY IMPACT ACROSS
NORTHERN ZONES BEING A SHIFT TO MORE WESTERLY WINDS. WINDS ALOFT
REMAIN FAIRLY STRONG AND COLD ADVECTION THROUGH TODAY WILL PROMOTE
MIXING OF THOSE STRONGER WINDS DOWN TO THE SURFACE ACROSS NORTHERN
ZONES THROUGH THIS AFTERNOON. STRONGEST WINDS WILL BE ALONG THE
NORTHERN ROCKY MTN FRONT AND GLACIER COUNTY...HOWEVER THE PERIOD
OF PEAK WINDS ALOFT HAS PASSED. STILL EXPECT SUSTAINED WINDS
NEAR 30KTS AT TIMES SO WILL LET THE HIGH WIND WARNING CONTINUE FOR
THOSE AREAS THROUGH THIS AFTERNOON. UNSTABLE AND SOMEWHAT MOIST
WESTERLY FLOW WILL MAINTAIN SCATTERED MTN SNOW SHOWERS THIS
AFTERNOON WITH MORE PERSISTENT SHOWER ACTIVITY EXPECTED OVER THE
GALLATIN/MADISON RANGES OF SW MT WHERE AN INCH OR TWO OF NEW SNOW
MAY FALL THROUGH THIS AFTERNOON. ELSEWHERE...DOWNSLOPE WESTERLY
FLOW WILL LIMIT PRECIPITATION CHANCES WITH PARTLY CLOUDY SKIES
ACROSS WESTERN PORTIONS OF NORTH CENTRAL MT. ONE EXCEPTION MAY BE
AREAS ALONG THE CANADIAN BORDER LATER THIS AFTERNOON AS A DISTURBANCE
DROPPING SE FROM ALBERTA MAY PRODUCE A FEW LIGHT SNOW SHOWERS OR
FLURRIES. HAVE MADE SOME MINOR ADJUSTMENTS TO POPS TO ACCOUNT FOR
THIS AND ALIGN WITH LATEST OBSERVATIONAL TRENDS. OTHERWISE...CURRENT
FORECAST IS IN GOOD SHAPE. HOENISCH
&&
.AVIATION...
UPDATED 1740Z.
AN UPPER LEVEL LOW PRESSURE TROUGH WILL CONTINUE TO MAKE ITS WAY
ACROSS CENTRAL MT THIS AFTN/EVE. MOST OF ASSOCIATED MOISTURE HAS
ALREADY PUSHED TOWARD KBIL BUT LOCATIONS WEST OF A KBIL-TO-KHLN LINE
WILL SEE A FEW RESIDUAL SNOWSHOWERS THROUGH MID-AFTN. CEILINGS
SHOULD REMAIN VFR ACROSS THE REGION...THOUGH HIGHER TERRAIN WILL BE
OBSCURED WITH MVFR/IFR CONDITIONS NEAR ANY PRECIPITATION AREAS.
WINDS WILL BE GUSTY OVER THE PLAINS AND ROCKY MTN FRONT THIS AFTN
WITH WIDESPREAD GUSTS OF 25 TO 35 KTS...AND SOME LOCATIONS FROM
GLACIER NP TO KHVR SEEING GUSTS OF 40 TO 50 KTS. AS THE TROUGH
MOVES FURTHER EAST THIS EVE...WINDS SHOULD DECREASE TOWARD SUNSET
AND SKIES WILL BE MOSTLY CLEAR OVERNIGHT AT ALL TERMINALS.
WARANAUSKAS
&&
.PREV DISCUSSION...
/ISSUED 510 AM MST SAT NOV 21 2009/
TODAY THROUGH MONDAY...PROGRESSIVE PATTERN WILL CONTINUE. ONE
UPPER TROUGH WILL MOVE THROUGH THE AREA TODAY INTO THIS EVENING. A
WEAK UPPER RIDGE WILL THEN MOVE OVER THE AREA BY LATE TONIGHT
BEFORE ANOTHER UPPER TROUGH MOVES THROUGH THE AREA SUNDAY NIGHT.
THEN THE NEXT UPPER RIDGE WILL APPROACH THE AREA LATE MONDAY. WITH
THE UPPER TROUGHS EXPECT SNOW OVER THE MOUNTAINS WITH A FAIR
CHANCE OF SOME SNOW IN THE SOUTHWEST VALLEYS. FOR EACH UPPER
TROUGH DO NOT SEE MORE THAN SIX INCHES OF SNOW IN THE MOUNTAINS
WHILE THE VALLEYS COULD RECEIVE UP TO AN INCH. ALTHOUGH DO NOT
PLAN ON ISSUING ANY WINTER WEATHER HIGHLIGHTS AT THIS POINT WILL
CONTINUE TO MENTION THE SNOW IN THE HAZARDOUS WEATHER OUTLOOK.
SPEAKING OF HIGHLIGHTS HAVE ISSUED A HIGH WIND WARNING FOR THE
NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS FOR TODAY. IT
APPEARS ATMOSPHERIC MIXING WILL BE ABLE TO TAP INTO 50 KNOT WINDS
JUST ABOVE THE SURFACE AT LEAST THIS MORNING. WITH THESE WEATHER
SYSTEMS DOWNSLOPE FLOW SHOULD KEEP THE PLAINS GENERALLY DRY. THE
SECOND UPPER TROUGH IS FORECAST TO HAVE MORE MOISTURE THAN THE
FIRST UPPER TROUGH SO WILL CONTINUE WITH THE MENTION OF A SLIGHT
CHANCE OF SNOW FOR LATE SUNDAY AND SUNDAY NIGHT. WITH THE UPPER
RIDGE APPROACHING ON MONDAY JUST EXPECT SOME LINGERING SNOW
SHOWERS OVER THE MOUNTAINS FROM SUNDAY NIGHTS SYSTEM. BLANK
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 25 41 27 / 10 0 20 20
CTB 42 23 39 26 / 0 0 20 20
HLN 43 23 41 26 / 20 0 30 30
BZN 37 13 37 16 / 50 0 30 40
WEY 31 8 30 12 / 90 30 80 60
DLN 34 14 34 13 / 40 0 40 40
HVR 48 19 45 25 / 20 10 10 10
LWT 43 18 38 21 / 10 0 10 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR MTZ009-010.
&&
$$
SHORT TERM...BLANK
LONG TERM...COULSTON
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 211646
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
946 AM MST SAT NOV 21 2009
.UPDATE...
UPPER LEVEL TROUGH IS PROGRESSING ACROSS THE REGION THIS MORNING
WHILE THE ASSOCIATED PACIFIC COLD FRONT HAS MOVED THROUGH ALL ZONES
AND WILL CONTINUE TO PROGRESS EAST INTO THE DAKOTAS BY THIS
AFTERNOON. A PERIOD OF SNOW OCCURRED WITH THE FRONTAL PASSAGE
ACROSS MUCH OF SW MT EARLY THIS MORNING...WITH ONLY IMPACT ACROSS
NORTHERN ZONES BEING A SHIFT TO MORE WESTERLY WINDS. WINDS ALOFT
REMAIN FAIRLY STRONG AND COLD ADVECTION THROUGH TODAY WILL PROMOTE
MIXING OF THOSE STRONGER WINDS DOWN TO THE SURFACE ACROSS NORTHERN
ZONES THROUGH THIS AFTERNOON. STRONGEST WINDS WILL BE ALONG THE
NORTHERN ROCKY MTN FRONT AND GLACIER COUNTY...HOWEVER THE PERIOD
OF PEAK WINDS ALOFT HAS PASSED. STILL EXPECT SUSTAINED WINDS
NEAR 30KTS AT TIMES SO WILL LET THE HIGH WIND WARNING CONTINUE FOR
THOSE AREAS THROUGH THIS AFTERNOON. UNSTABLE AND SOMEWHAT MOIST
WESTERLY FLOW WILL MAINTAIN SCATTERED MTN SNOW SHOWERS THIS
AFTERNOON WITH MORE PERSISTENT SHOWER ACTIVITY EXPECTED OVER THE
GALLATIN/MADISON RANGES OF SW MT WHERE AN INCH OR TWO OF NEW SNOW
MAY FALL THROUGH THIS AFTERNOON. ELSEWHERE...DOWNSLOPE WESTERLY
FLOW WILL LIMIT PRECIPITATION CHANCES WITH PARTLY CLOUDY SKIES
ACROSS WESTERN PORTIONS OF NORTH CENTRAL MT. ONE EXCEPTION MAY BE
AREAS ALONG THE CANADIAN BORDER LATER THIS AFTERNOON AS A DISTURBANCE
DROPING SE FROM ALBERTA MAY PRODUCE A FEW LIGHT SNOW SHOWERS OR
FLURRIES. HAVE MADE SOME MINOR ADJUSTMENTS TO POPS TO ACCOUNT FOR
THIS AND ALIGN WITH LATEST OBSERVATIONAL TRENDS. OTHERWISE...CURRENT
FORECAST IS IN GOOD SHAPE. HOENISCH
&&
.AVIATION...
UPDATED 1210Z.
AN UPPER LEVEL LOW PRESSURE TROUGH OVER THE PACIFIC NORTHWEST WILL
CONTINUE TO OBSCURE THE MOUNTAIN AREAS OF WESTERN...SOUTHWEST...AND
CENTRAL MONTANA IN CLOUDS AND SNOW SHOWERS THIS MORNING. THE KHLN
TERMINAL MAY ALSO LOWER TO MVFR CONDITIONS IN RAIN/SNOW SHOWERS AT
TIMES THIS MORNING...WHILE LOCAL UPSLOPE CONDITIONS AT KBZN WILL
LOWER CONDITIONS TO IFR LEVELS AT TIMES DUE TO HEAVIER SNOW SHOWERS.
PRECIPITATION WILL DECREASE DURING THE AFTERNOON AS THE UPPER TROUGH
MOVES INTO THE AREA. GUSTY WESTERLY WINDS WILL ALSO INCREASE
SIGNIFICANTLY THIS MORNING AS AN ASSOCIATED COLD FRONT MOVES EAST
ACROSS THE AREA. WINDS WILL BE ESPECIALLY STRONG ALONG THE EAST
SLOPES OF THE ROCKIES...WHERE GUSTS COULD REACH 50 KT AT TIMES.
HOWEVER...THE DOWNSLOPE EFFECT OF THE WINDS OVER THE PLAINS OF NORTH
CENTRAL AND CENTRAL MONTANA WILL LIMIT PRECIPITATION TO AN ISOLATED
SHOWER OR TWO AT BEST THERE. AN UPPER LEVEL RIDGE OF HIGH PRESSURE
WILL THEN MOVE INTO THE AREA AFTER 00Z SUNDAY FOR CLEARING SKIES AND
DECREASING WINDS OVERNIGHT. COULSTON
&&
.PREV DISCUSSION...
/ISSUED 510 AM MST SAT NOV 21 2009/
TODAY THROUGH MONDAY...PROGRESSIVE PATTERN WILL CONTINUE. ONE
UPPER TROUGH WILL MOVE THROUGH THE AREA TODAY INTO THIS EVENING. A
WEAK UPPER RIDGE WILL THEN MOVE OVER THE AREA BY LATE TONIGHT
BEFORE ANOTHER UPPER TROUGH MOVES THROUGH THE AREA SUNDAY NIGHT.
THEN THE NEXT UPPER RIDGE WILL APPROACH THE AREA LATE MONDAY. WITH
THE UPPER TROUGHS EXPECT SNOW OVER THE MOUNTAINS WITH A FAIR
CHANCE OF SOME SNOW IN THE SOUTHWEST VALLEYS. FOR EACH UPPER
TROUGH DO NOT SEE MORE THAN SIX INCHES OF SNOW IN THE MOUNTAINS
WHILE THE VALLEYS COULD RECEIVE UP TO AN INCH. ALTHOUGH DO NOT
PLAN ON ISSUING ANY WINTER WEATHER HIGHLIGHTS AT THIS POINT WILL
CONTINUE TO MENTION THE SNOW IN THE HAZARDOUS WEATHER OUTLOOK.
SPEAKING OF HIGHLIGHTS HAVE ISSUED A HIGH WIND WARNING FOR THE
NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS FOR TODAY. IT
APPEARS ATMOSPHERIC MIXING WILL BE ABLE TO TAP INTO 50 KNOT WINDS
JUST ABOVE THE SURFACE AT LEAST THIS MORNING. WITH THESE WEATHER
SYSTEMS DOWNSLOPE FLOW SHOULD KEEP THE PLAINS GENERALLY DRY. THE
SECOND UPPER TROUGH IS FORECAST TO HAVE MORE MOISTURE THAN THE
FIRST UPPER TROUGH SO WILL CONTINUE WITH THE MENTION OF A SLIGHT
CHANCE OF SNOW FOR LATE SUNDAY AND SUNDAY NIGHT. WITH THE UPPER
RIDGE APPROACHING ON MONDAY JUST EXPECT SOME LINGERING SNOW
SHOWERS OVER THE MOUNTAINS FROM SUNDAY NIGHTS SYSTEM. BLANK
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 25 41 27 / 10 0 20 20
CTB 42 23 39 26 / 0 0 20 20
HLN 43 23 41 26 / 20 0 30 30
BZN 37 13 37 16 / 50 0 30 40
WEY 31 8 30 12 / 90 30 80 60
DLN 34 14 34 13 / 40 0 40 40
HVR 48 19 45 25 / 20 10 10 10
LWT 43 18 38 21 / 10 0 10 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR MTZ009-010.
&&
$$
SHORT TERM...BLANK
LONG TERM...COULSTON
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 211627 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
927 AM MST SAT NOV 21 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
A VIGOROUS PACIFIC TROUGH AND COLD FRONT ARE IN THE PROCESS OF
CROSSING NORTHEAST MONTANA THIS MORNING. A STRONG WEST WIND IS
DEVELOPING IN THE WAKE OF THE FRONT WITH THE WESTERN ZONES
BEGINNING TO EXPERIENCE WIND SPEEDS IN EXCESS OF 20 MPH...WITH
GUSTS ABOVE 30 MPH. THE WIND SHOULD INCREASE ACROSS THE ENTIRE
AREA TODAY WITH COLD AIR ADVECTION AND STRONG SUBSIDENCE BEHIND
THE TROUGH. THE CURRENT LAKE WIND ADVISORY AND ITS TIME DURATION
REMAIN REASONABLE. OVERNIGHT RELATIVE HUMIDITY RECOVERY AHEAD OF
THE FRONT WAS VERY POOR IN THE LITTLE ROCKIES AND MISSOURI BREAKS
REGION. HOWEVER...DEWPOINTS ARE INCREASING...AND TEMPERATURES ARE
FALLING SLIGHTLY HENCE RELATIVE HUMIDITY IS RECOVERING THIS
MORNING. A BRIEF PERIOD OF LOW RELATIVE HUMIDITY IS STILL EXPECTED
THIS AFTERNOON...BUT THE MORNING RECOVERY SHOULD PRECLUDE ANY FIRE
WEATHER HIGHLIGHTS. THE OVERALL FORECAST IS IN GOOD SHAPE AND THE
PRIMARY UPDATE INVOLVED BLENDING OVERNIGHT RELATIVE HUMIDITY
PERCENTAGES TO FORECAST VALUES IN ORDER TO DIAGNOSE WHETHER A
FIRE WEATHER HIGHLIGHT WAS NECESSARY OR NOT. AJZ
PREVIOUS SHORT TERM DISCUSSION...
AN ENERGETIC SHORT WAVE TROUGH AND COLD FRONT SWEEP OVER THE
ZONES TODAY. THE MAIN EFFECT WILL BE STRONG WINDS WESTERLY WINDS
BEHIND THE FRONT. A STRONG SURFACE TROUGH ANCHORED BY A LOW
CENTERED IN SOUTHERN SASKATCHEWAN WILL MAINTAIN A STRONG PRESSURE
GRADIENT ACROSS THE SURFACE. THESE WINDS WILL BE REINFORCED BY
850MB WINDS OF 35-40KTS RESULTING IN SURFACE WIND GUSTS OF EQUAL
STRENGTH. THE LWA SEEMS LIKE A SLAM-DUNK SO WILL RENEW THE NPW
DURING THIS PACKAGE. MOISTURE IS RATHER ANEMIC WITH THIS SYSTEM SO
EXPECT MOSTLY CLOUD COVER WITH LITTLE PRECIPITATION. A VORT MAX
AROUND THE BASE OF THE UPPER LEVEL TROUGH COULD PRODUCE SOME
MOISTURE IN SOUTHERN ALBERTA/SASKATCHEWAN THAT MIGHT SPREAD A BIT
ACROSS THE INTERNATIONAL BORDER. SO WILL MAINTAIN POPS JUST BELOW
TEXT MENTION FOR NOW. THE OTHER PREVIOUSLY MENTIONED CONCERN WAS
THE EXPECTED LOW RH VALUES FOR TODAY WHICH COULD PRODUCE NEAR
CRITICAL FIRE WEATHER CONDITIONS. SEE FIRE WX SEPARATE DISCUSSION
BELOW.
TONIGHT/SUNDAY...UPPER FLOW VEERS TO THE NORTHWEST LATE TONIGHT AS
THE UPPER TROUGH BASE MOVES EAST. A SHORT WAVE UPPER RIDGE FOLLOWS
BUT IS QUICKLY FOLLOWED BY THE NEXT SHORT WAVE TROUGH. THIS NEXT
WAVE SENDS A WEAK COLD FRONT INTO THE CWA BY AFTERNOON WHICH COULD
PRODUCE LIGHT PRECIPITATION OVER THE WESTERN ZONES. 850MB
TEMPERATURES REMAIN NEAR 0*C OR JUST BELOW SO MIXED PRECIPITATION
IS A POSSIBILITY. WITH THE ATMOSPHERE DECOUPLING AT SUNSET...THE
RELAXING GRADIENT WILL ALLOW WINDS TO DROP BELOW LWA CRITERIA.
SUNDAY NIGHT/MONDAY...THE BASE OF THE TROUGH DROPS SOUTH INTO
NORTHERN COLORADO...TAKING MOST OF THE ENERGY TO OUR SOUTH.
HOWEVER THE INVERTED SURFACE EXTENDS NORTH INTO NORTHEASTERN
MONTANA WHICH WILL KEEP CONDITIONS A BIT UNSETTLED. WHILE
NAM...UKMET AND EC STAY DRY...BASED ON GFS...GEM AND SREF...SLIGHT
CHANCE POPS SEEM APPROPRIATE FOR SNOW OVERNIGHT. CONDITIONS DO
NOT CHANGE MUCH FOR MONDAY SO WILL KEEP SLIGHT CHANCE POPS GOING.
SURFACE HIGHS WILL DROP DOWN MUCH CLOSER TO NORMAL WHILE 850MB
TEMPERATURES HOVER AROUND -4*C. SO EXPECT ANY PRECIPITATION TO
FALL AS SNOW AND POSSIBLY RAIN SHOWERS. QPF AMOUNTS WILL NOT
PRODUCE ACCUMULATIONS. SCT
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
SHORTWAVE TROUGH DROPS SOUTHEAST OUT OF SASKATCHEWAN DURING THE
DAY TUESDAY AND MAY BRING A SLIGHT CHANCE OF RAIN OR SNOW. THIS
FAST MOVING SYSTEM WILL HAVE LIMITED MOISTURE WITH IT.
AN UPPER RIDGE BUILDS INTO THE AREA ON WEDNESDAY AND WILL BRING
WARM AND DRY WEATHER THROUGH THANKSGIVING DAY FOR SURE.
MODELS HAVE SOME DIFFERENCES ON TRACK OF A SHORTWAVE THAT MOVES
INLAND FROM THE PACIFIC ON FRIDAY. ECMWF TAKES THE SYSTEM SOUTH OF
THE AREA WHILE THE GFS BRINGS IT ACROSS MONTANA. EITHER WAY...A
COLD FRONT WILL AFFECT THE FORECAST AREA ON FRIDAY WITH COOLER
TEMPERATURES EXPECTED NEXT WEEKEND. WILL KEEP THE FORECAST DRY FOR
THE MOST PART FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. A MIX OF MID AND HIGH LEVEL CLOUDS WILL MOVE
THROUGH THE AREA TODAY WITH CEILINGS ABOVE 10 000 FT AND NO
OBSTRUCTIONS TO VISIBILITY. SKIES CLEARING TONIGHT. WEST WINDS
THIS MORNING WILL INCREASE TO 20 TO 25 KNOTS BY 18Z WITH HIGHER
GUSTS. THE WINDS WILL DIMINISH TO AROUND 10 KTS AFTER SUNSET.
&&
.FIRE WEATHER...
A STRONG WEST WIND WILL DEVELOP TODAY BEHIND A COLD FRONT. WIND
SPEEDS ARE EXPECTED TO REACH 20 TO 30 MPH...WITH GUSTS TO 40 MPH
DURING THE LATE MORNING AND AFTERNOON HOURS. AFTERNOON MINIMUM
RELATIVE HUMIDITY VALUES ARE EXPECTED TO BRIEFLY DROP INTO THE 20
TO 30 PERCENT RANGE BEFORE BEGINNING A STEADY RECOVERY NEAR
SUNSET. THEREFORE...A BRIEF PERIOD OF CRITICAL FIRE WEATHER
CONDITIONS ARE POSSIBLE THIS AFTERNOON...BUT HIGHLIGHTS ARE NOT
EXPECTED AT THIS TIME DUE TO THE SHORT DURATION OF LOW RELATIVE
HUMIDITY DUE TO SHORTENING SUNLIGHT HOURS. THE MOST SUSCEPTIBLE
AREAS WILL BE THE LITTLE ROCKY MOUNTAINS AND THE MISSOURI BREAKS
REGION OF ZONES 119 AND 121...WHICH EXPERIENCED A RATHER POOR
RELATIVE HUMIDITY RECOVERY LAST NIGHT. AJZ/SCT
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR FORT PECK
LAKE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 211537
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
837 AM MST SAT NOV 21 2009
.SHORT TERM...VALID FOR TDY AND SUN...
COLD FRONT MOVING ACROSS THE REGION THIS MORNING WITH
PRECIPITATION LIMITED TO THE MOUNTAINS AS DOWNSLOPE IS HAVING A
BIG IMPACT ON PLAINS. BIGGER STORY IS WINDS ACROSS THE REGION AS
THEY ARE A MIX OF MOMENTUM MIX DOWN...PRESSURE RISES AND
GRADIENTS...AND EVAPORTIVE COOLING FROM DYING SHOWERS. HAVE
UPDATED FORECASTS TO INDICATE STRONGER WINDS AND SPECIFICALLY A
TENDENCY FOR WINDS TO BE GUSTY IN NATURE. ALSO...DECREASED
PRECIPITATION CHANCES ACROSS MOST OF THE PLAINS TO SPRINKLES.
TEMPERATURES A DIFFERENT CHALLENGE AS PROBABLY WILL BE COOLING IN
THE WEST WHILE STILL WARMING A BIT IN THE EAST FOR A COUPLE OF HOURS.
UPDATES ALREADY SENT. WINDS WILL DECREASE THIS EVENING AND IT
SHOULD BE A MUCH COOLER NIGHT. BORSUM
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
A PROGRESSIVE PATTERN DEVELOPS OVER THE FORECAST AREA FOR THE
EXTENDED. 3 SYSTEMS WILL IMPACT THE AREA NEXT WEEK...BUT
RIDGING ON THANKSGIVING BRINGS WARM...DRY AND BREEZY CONDITIONS TO
THE AREA. THE FIRST SYSTEM IS OVER THE AREA MONDAY...SHIFTING
SOUTHEAST MONDAY NIGHT. INCREASED POPS OVER EASTERN AREAS MONDAY
AS WELL AS KEEPING SOME POPS FOR WESTERN MOUNTAIN AND FOOTHILLS
LOCATIONS. TEMPERATURES DON`T LOOK TERRIBLY COLD WITH THIS SYSTEM
IN THE LOWER 40S...AND COULD BE A TAD COOLER IN SOME LOCATIONS
WHERE CLOUDS AND PRECIPITATION OCCUR. AN ALBERTA CLIPPER SYSTEM
QUICKLY MOVES THROUGH EASTERN AREAS ON TUESDAY AFTERNOON...THOUGH
NOT BEFORE TEMPERATURES CLIMB INTO THE LOW TO MID 40S. IF TIMING
OF THE CLIPPER IS FASTER WILL NEED TO COOL EASTERN AREAS 5 TO 10
DEGREES. RIDGING BUILDS INTO THE AREA WEDNESDAY AND THURSDAY WITH
DOWNSLOPE WIND GRADIENT IN PLACE PUSHING TEMPERATURES BACK INTO
THE 50S. THE FINAL SYSTEM ARRIVES FRIDAY OR SATURDAY DEPENDING ON
MODEL PREFERENCE. THE ECMWF DIGS THE LATE WEEK SYSTEM FURTHER TO
THE SOUTH AND BRINGS COOLER AIR INTO THE AREA FRIDAY
AFTERNOON...WHILE THE GFS IS LESS DEEP WITH THE SYSTEM KEEPING THE
ENERGY OVER MONTANA AND WYOMING AND BRINGS COLDER AIR IN FOR
SATURDAY. 00Z ENSEMBLE DATA SUPPORTIVE OF THE OPERATIONAL GFS
KEEPING TROF FURTHER NORTH...AND TRENDED FORECAST TOWARD THE GFS
FOR THE LATER PERIODS...INCLUDING INCREASING POPS AND LOWERING
TEMPERATURES JUST A TAD. CHAMBERS
&&
.AVIATION...
COLD FRONT WILL CONTINUE TO MOVE ACROSS THE AREA THIS MORNING
BRINGING GUSTY WINDS UP TO 40 KNOTS. GUSTY WINDS UP TO 30 KNOTS
WILL CONTINUE BEHIND THE FRONT THROUGH EARLY EVENING. MVFR
CONDITIONS AND MOUNTAIN OBSCURATIONS WILL BE POSSIBLE THROUGH THE
DAY ACROSS THE WESTERN ROUTES...INCLUDING THE KLVM AREA ...WHERE
SCATTERED SNOW SHOWERS WILL CONTINUE. ACROSS THE OTHER
AREAS...SPRINKLES WILL BE POSSIBLE WITH VFR CONDITIONS
PREVAILING. SOLUM
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 048 023/040 028/042 024/046 030/051 036/055 035/051
1/N 02/W 21/B 11/B 00/B 00/U 02/W
LVM 041 020/036 020/035 018/043 025/050 029/054 031/046
4/W 04/J 32/J 12/W 10/B 00/B 03/W
HDN 051 024/043 024/044 019/047 025/052 031/057 030/053
1/M 02/W 22/W 12/W 00/B 00/U 02/W
MLS 053 022/045 024/043 020/047 023/046 030/056 031/051
1/N 02/W 22/W 22/W 10/B 00/U 01/U
4BQ 051 023/042 021/042 019/045 022/046 028/056 029/051
1/N 22/W 22/J 12/W 00/B 00/U 01/U
BHK 053 021/045 021/040 019/043 020/040 024/054 027/051
1/N 11/B 22/J 22/W 10/B 00/U 01/U
SHR 047 020/043 022/039 014/046 024/050 028/056 028/051
2/W 22/W 22/J 11/B 00/B 00/U 01/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 211210
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
510 AM MST SAT NOV 21 2009
...UPDATE TO AVIATION...
.DISCUSSION...
TODAY THROUGH MONDAY...PROGRESSIVE PATTERN WILL CONTINUE. ONE
UPPER TROUGH WILL MOVE THROUGH THE AREA TODAY INTO THIS EVENING. A
WEAK UPPER RIDGE WILL THEN MOVE OVER THE AREA BY LATE TONIGHT
BEFORE ANOTHER UPPER TROUGH MOVES THROUGH THE AREA SUNDAY NIGHT.
THEN THE NEXT UPPER RIDGE WILL APPROACH THE AREA LATE MONDAY. WITH
THE UPPER TROUGHS EXPECT SNOW OVER THE MOUNTAINS WITH A FAIR
CHANCE OF SOME SNOW IN THE SOUTHWEST VALLEYS. FOR EACH UPPER
TROUGH DO NOT SEE MORE THAN SIX INCHES OF SNOW IN THE MOUNTAINS
WHILE THE VALLEYS COULD RECEIVE UP TO AN INCH. ALTHOUGH DO NOT
PLAN ON ISSUING ANY WINTER WEATHER HIGHLIGHTS AT THIS POINT WILL
CONTINUE TO MENTION THE SNOW IN THE HAZARDOUS WEATHER OUTLOOK.
SPEAKING OF HIGHLIGHTS HAVE ISSUED A HIGH WIND WARNING FOR THE
NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS FOR TODAY. IT
APPEARS ATMOSPHERIC MIXING WILL BE ABLE TO TAP INTO 50 KNOT WINDS
JUST ABOVE THE SURFACE AT LEAST THIS MORNING. WITH THESE WEATHER
SYSTEMS DOWNSLOPE FLOW SHOULD KEEP THE PLAINS GENERALLY DRY. THE
SECOND UPPER TROUGH IS FORECAST TO HAVE MORE MOISTURE THAN THE
FIRST UPPER TROUGH SO WILL CONTINUE WITH THE MENTION OF A SLIGHT
CHANCE OF SNOW FOR LATE SUNDAY AND SUNDAY NIGHT. WITH THE UPPER
RIDGE APPROACHING ON MONDAY JUST EXPECT SOME LINGERING SNOW
SHOWERS OVER THE MOUNTAINS FROM SUNDAY NIGHTS SYSTEM. BLANK
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.AVIATION...
UPDATED 1210Z.
AN UPPER LEVEL LOW PRESSURE TROUGH OVER THE PACIFIC NORTHWEST WILL
CONTINUE TO OBSCURE THE MOUNTAIN AREAS OF WESTERN...SOUTHWEST...AND
CENTRAL MONTANA IN CLOUDS AND SNOW SHOWERS THIS MORNING. THE KHLN
TERMINAL MAY ALSO LOWER TO MVFR CONDITIONS IN RAIN/SNOW SHOWERS AT
TIMES THIS MORNING...WHILE LOCAL UPSLOPE CONDITIONS AT KBZN WILL
LOWER CONDITIONS TO IFR LEVELS AT TIMES DUE TO HEAVIER SNOW SHOWERS.
PRECIPITATION WILL DECREASE DURING THE AFTERNOON AS THE UPPER TROUGH
MOVES INTO THE AREA. GUSTY WESTERLY WINDS WILL ALSO INCREASE
SIGNIFICANTLY THIS MORNING AS AN ASSOCIATED COLD FRONT MOVES EAST
ACROSS THE AREA. WINDS WILL BE ESPECIALLY STRONG ALONG THE EAST
SLOPES OF THE ROCKIES...WHERE GUSTS COULD REACH 50 KT AT TIMES.
HOWEVER...THE DOWNSLOPE EFFECT OF THE WINDS OVER THE PLAINS OF NORTH
CENTRAL AND CENTRAL MONTANA WILL LIMIT PRECIPITATION TO AN ISOLATED
SHOWER OR TWO AT BEST THERE. AN UPPER LEVEL RIDGE OF HIGH PRESSURE
WILL THEN MOVE INTO THE AREA AFTER 00Z SUNDAY FOR CLEARING SKIES AND
DECREASING WINDS OVERNIGHT. COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 25 41 27 / 10 0 20 20
CTB 42 23 39 26 / 10 0 20 20
HLN 43 23 41 26 / 20 0 30 30
BZN 37 13 37 16 / 50 0 30 40
WEY 31 8 30 12 / 90 30 80 60
DLN 34 14 34 13 / 50 0 40 40
HVR 48 19 45 25 / 10 10 10 10
LWT 43 18 38 21 / 10 0 10 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR MTZ009-010.
&&
$$
SHORT TERM...BLANK
LONG TERM...COULSTON
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 211058
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
358 AM MST SAT NOV 21 2009
.DISCUSSION...
TODAY THROUGH MONDAY...PROGRESSIVE PATTERN WILL CONTINUE. ONE
UPPER TROUGH WILL MOVE THROUGH THE AREA TODAY INTO THIS EVENING. A
WEAK UPPER RIDGE WILL THEN MOVE OVER THE AREA BY LATE TONIGHT
BEFORE ANOTHER UPPER TROUGH MOVES THROUGH THE AREA SUNDAY NIGHT.
THEN THE NEXT UPPER RIDGE WILL APPROACH THE AREA LATE MONDAY. WITH
THE UPPER TROUGHS EXPECT SNOW OVER THE MOUNTAINS WITH A FAIR
CHANCE OF SOME SNOW IN THE SOUTHWEST VALLEYS. FOR EACH UPPER
TROUGH DO NOT SEE MORE THAN SIX INCHES OF SNOW IN THE MOUNTAINS
WHILE THE VALLEYS COULD RECEIVE UP TO AN INCH. ALTHOUGH DO NOT
PLAN ON ISSUING ANY WINTER WEATHER HIGHLIGHTS AT THIS POINT WILL
CONTINUE TO MENTION THE SNOW IN THE HAZARDOUS WEATHER OUTLOOK.
SPEAKING OF HIGHLIGHTS HAVE ISSUED A HIGH WIND WARNING FOR THE
NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS FOR TODAY. IT
APPEARS ATMOSPHERIC MIXING WILL BE ABLE TO TAP INTO 50 KNOT WINDS
JUST ABOVE THE SURFACE AT LEAST THIS MORNING. WITH THESE WEATHER
SYSTEMS DOWNSLOPE FLOW SHOULD KEEP THE PLAINS GENERALLY DRY. THE
SECOND UPPER TROUGH IS FORECAST TO HAVE MORE MOISTURE THAN THE
FIRST UPPER TROUGH SO WILL CONTINUE WITH THE MENTION OF A SLIGHT
CHANCE OF SNOW FOR LATE SUNDAY AND SUNDAY NIGHT. WITH THE UPPER
RIDGE APPROACHING ON MONDAY JUST EXPECT SOME LINGERING SNOW
SHOWERS OVER THE MOUNTAINS FROM SUNDAY NIGHTS SYSTEM. BLANK
MONDAY NIGHT THROUGH SATURDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT INTO THE MIDDLE OF NEXT WEEK. BOTH MODELS BRING A
WEAK SHORTWAVE TROUGH OVER AN UPPER LEVEL HIGH PRESSURE RIDGE PARKED
ALONG THE PACIFIC COAST THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...WHICH WILL BRING A CHANCE OF PRECIPITATION TO THE AREA.
THIS SHORTWAVE WILL ALSO BRING STRONG AND GUSTY WESTERLY DOWNSLOPE
WINDS TO THE AREA...WHICH WILL LIMIT PRECIPITATION OVER THE PLAINS
AND WARM TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE SEASONAL
AVERAGES. BOTH MODELS THEN AMPLIFY AND SHIFT THE UPPER RIDGE INTO
MONTANA TUESDAY NIGHT INTO THURSDAY. THIS RIDGE WILL KEEP THE AREA
WARM (TEMPERATURES 10 TO 15 DEGREES ABOVE NORMAL) AND MOSTLY DRY.
GUSTY WESTERLY SURFACE WINDS WILL INCREASE AGAIN WEDNESDAY NIGHT
INTO THURSDAY (THANKSGIVING DAY) AS THE NEXT SYSTEM APPROACHES THE
AREA. THE MODELS BEGIN TO DIFFER ON THURSDAY. UNLIKE THE MODEL RUNS
FROM LAST NIGHT...THE ECMWF BRINGS THE NEXT PACIFIC SYSTEM THROUGH
THE STATE QUICKER THAN THE GFS. WITH THIS UNCERTAINTY...HAVE KEPT
NEAR CLIMATOLOGICAL CHANCES OF PRECIPITATION OVER THE TFX CWA FRIDAY
THROUGH SATURDAY...WITH TEMPERATURES COOLING TO NEAR SEASONAL
NORMALS BY SATURDAY. AN UPPER LEVEL RIDGE THEN BEGINS TO MOVE INTO
THE WESTERN UNITED STATES SATURDAY NIGHT...WHICH SHOULD CAUSE THE
CHANCE FOR PRECIPITATION TO DECREASE. UPPER LEVEL SUPPORT FOR THE
INCREASING WINDS THROUGH THIS PERIOD IS TEMPORARY. THEREFORE...AM
NOT ANTICIPATING HIGH WIND HIGHLIGHTS AT THIS TIME AND WILL NOT
MENTION IN THE HAZARDOUS WEATHER OUTLOOK. HOWEVER...THE POTENTIAL
FOR BRIEF PERIODS OF STRONG WINDS STILL REMAINS...AND THE SITUATION
WILL CONTINUE TO BE MONITORED. COULSTON
&&
.AVIATION...
UPDATED 0600Z.
AN UPPER LEVEL TROF OF LOW PRESSURE WILL MOVE EASTWARD TOWARDS
CENTRAL/SOUTHWEST MONTANA LATE TONIGHT. EXPECT GENERALLY OVERCAST
CONDITIONS UNTIL 00Z SUNDAY...WITH THE CHANCE FOR SNOW DEVELOPING
AFTER 09Z OVER WESTERN AND SOUTHWESTERN MONTANA. THE BEST CHANCE FOR
SNOW ON SATURDAY WILL BE ON SATURDAY FROM 13Z TO 20Z IN THE BOZEMAN
AND WEST YELLOWSTONE AREA. THUS IFR/LIFR CONDITIONS WILL BE POSSIBLE
AT TIMES OVER THIS REGION. MOUNTAINS WILL BE OBSCURED AT TIMES
THROUGHOUT THE REGION THOUGH THE PERIOD. ADDITIONALLY...EXPECT
SURFACE WINDS TO BECOME VERY BREEZY OVER NORTH CENTRAL MONTANA AFTER
09Z SATURDAY. EXPECT A GENERALLY CLEARING TREND WITH LIGHTER WINDS
EXPECTED FROM 0Z SUNDAY UNTIL 6Z SUNDAY. BRUSDA
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 25 41 27 / 10 0 20 20
CTB 42 23 39 26 / 10 0 20 20
HLN 43 23 41 26 / 20 0 30 30
BZN 37 13 37 16 / 50 0 30 40
WEY 31 8 30 12 / 90 30 80 60
DLN 34 14 34 13 / 50 0 40 40
HVR 48 19 45 25 / 10 10 10 10
LWT 43 18 38 21 / 10 0 10 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 5 PM MST THIS AFTERNOON FOR MTZ009-010.
&&
$$
SHORT TERM...BLANK
LONG TERM...COULSTON
AVIATION...COULSTON
WEATHER.GOV/GREATFALLS
000
FXUS65 KMSO 211042
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
342 AM MST SAT NOV 21 2009
.DISCUSSION...A VIGOROUS COLD FRONT HAS CROSSED MUCH OF THE NORTHERN
ROCKIES EARLY THIS MORNING AND WILL BE EAST OF THE CONTINENTAL
DIVIDE BY SUNRISE. THIS FEATURE HAS PRODUCED A COUPLE TO SEVERAL
INCHES OF SNOW MAINLY ACROSS NORTH CENTRAL IDAHO AS INDICATED BY
SNOTEL SENSORS AND HIGHWAY CAMERAS AT LOLO AND LOST TRAIL PASSES.
STRONG WINDS...PARTICULARLY IN THE MOUNTAINS HAVE ALSO RESULTED
FROM THE FRONTAL PASSAGES. THE AIR MASS BEHIND THE FRONT AND UNDER
A PASSING UPPER LEVEL TROUGH WILL BE VERY UNSTABLE AND MOIST
THROUGH MIDDAY. THEREFORE...ALL AREAS WILL SEE SNOW SHOWERS
DEVELOP. NORTH CENTRAL IDAHO WILL CONTINUE TO SEE THE BEST
ACCUMULATIONS...AND THUS THE WINTER WEATHER ADVISORY WILL BE
CONTINUED THROUGH LATE MORNING. BLOWING SNOW MAY CAUSE AREAS OF
POOR VISIBILITY IN THE MOUNTAINS AS WINDS ARE EXPECTED TO STAY
BREEZY.
A SECOND SYSTEM WILL BARREL INTO THE NORTHERN ROCKIES SUNDAY. THIS
WILL ALSO BE A GOOD SNOW PRODUCER SIMILAR TO THE CURRENT TROUGH.
AND AGAIN NORTH CENTRAL IDAHO WILL SEE THE GREATEST
ACCUMULATIONS AND HAVE ISSUED A SECOND WINTER WEATHER ADVISORY FOR
THAT AREA SUNDAY THROUGH SUNDAY EVENING. THE BITTERROOTS WILL ALSO
SEE SEVERAL INCHES OF SNOW WITH THIS EVENT FROM LOOKOUT PASS AREA
SOUTH TO LOST TRAIL PASS...SO HAVE INCLUDED THIS AREA IN THE
ADVISORY. THIS SYSTEM WILL ALSO HAVE INCREASED WINDS WITH SOME
BLOWING SNOW POSSIBLE.
LIGHT ACCUMULATION IN THE VALLEYS ARE POSSIBLE BOTH TODAY AND WITH
SUNDAY`S SYSTEM AS SNOW LEVELS HAVE LOWERED TO ALL BUT THE LOWEST
VALLEYS IN NORTH CENTRAL IDAHO.
MONDAY THROUGH THE WEEK...THE NORTHERN ROCKIES WILL ENTER INTO A
RIDGING PATTERN THROUGH THE BULK OF NEXT WEEK. THE FIRST HINTS OF A
RIDGE OF HIGH PRESSURE WILL FORM THROUGHOUT THE DAY MONDAY...BUT
MAY BE INTERRUPTED BY A SHORTWAVE PASSING TO THE NORTH IN CANADA.
WHILE THIS WAVE DOESNT LOOK TO MOVE FAR ENOUGH SOUTH TO HAVE ANY
TRUE AFFECTS ON THE REGION...FLOW WILL REMAIN UNSTABLE
ENOUGH IN NORTHWEST MONTANA FOR SHOWERY PRECIPITATION TO
OCCUR BUT REMAIN CONFINED MOSTLY TO HIGHER ELEVATIONS. HIGH
PRESSURE WILL THEN HAVE A BETTER CHANCE TO REBUILD OVER THE
NORTHERN ROCKIES TUESDAY NIGHT AND WILL CONTINUE TO STRENGTHEN
THROUGH THE END OF THE WEEK.
&&
.AVIATION...SNOW SHOWERS WILL DEVELOP UNDER AN UNSTABLE UPPER
TROUGH THROUGH THE MORNING CAUSING INTERMITTENT VISIBILITY AND
CEILING REDUCTIONS AT ALL TERMINALS. THE SHOWERS WILL DECREASE
SOMEWHAT IN COVERAGE BY LATE AFTERNOON BUT LIKELY CONTINUE OVER
THE MOUNTAINS INTO THE EARLY EVENING.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY FROM 5 AM TO 11 PM MST SUNDAY FOR
LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY FROM 5 AM TO 11 PM MST SUNDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY FROM 4 AM TO 10 PM PST SUNDAY FOR
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...WHITMORE
LONG TERM....ALLEGRETTO
AVIATION...WHITMORE
000
FXUS65 KGGW 210947
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
247 AM MST SAT NOV 21 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
AN ENERGETIC SHORT WAVE TROUGH AND COLD FRONT SWEEP OVER THE ZONES
TODAY. THE MAIN EFFECT WILL BE STRONG WINDS WESTERLY WINDS BEHIND
THE FRONT. A STRONG SURFACE TROUGH ANCHORED BY A LOW CENTERED IN
SOUTHERN SASKATCHEWAN WILL MAINTAIN A STRONG PRESSURE GRADIENT
ACROSS THE SURFACE. THESE WINDS WILL BE REINFORCED BY 850MB WINDS
OF 35-40KTS RESULTING IN SURFACE WIND GUSTS OF EQUAL STRENGTH. THE
LWA SEEMS LIKE A SLAM-DUNK SO WILL RENEW THE NPW DURING THIS
PACKAGE. MOISTURE IS RATHER ANEMIC WITH THIS SYSTEM SO EXPECT
MOSTLY CLOUD COVER WITH LITTLE PRECIPITATION. A VORT MAX AROUND
THE BASE OF THE UPPER LEVEL TROUGH COULD PRODUCE SOME MOISTURE IN
SOUTHERN ALBERTA/SASKATCHEWAN THAT MIGHT SPREAD A BIT ACROSS THE
INTERNATIONAL BORDER. SO WILL MAINTAIN POPS JUST BELOW TEXT
MENTION FOR NOW. THE OTHER PREVIOUSLY MENTIONED CONCERN WAS THE
EXPECTED LOW RH VALUES FOR TODAY WHICH COULD PRODUCE NEAR CRITICAL
FIRE WEATHER CONDITIONS. SEE FIRE WX SEPARATE DISCUSSION BELOW.
TONIGHT/SUNDAY...UPPER FLOW VEERS TO THE NORTHWEST LATE TONIGHT AS
THE UPPER TROUGH BASE MOVES EAST. A SHORT WAVE UPPER RIDGE FOLLOWS
BUT IS QUICKLY FOLLOWED BY THE NEXT SHORT WAVE TROUGH. THIS NEXT
WAVE SENDS A WEAK COLD FRONT INTO THE CWA BY AFTERNOON WHICH COULD
PRODUCE LIGHT PRECIPITATION OVER THE WESTERN ZONES. 850MB
TEMPERATURES REMAIN NEAR 0*C OR JUST BELOW SO MIXED PRECIPITATION
IS A POSSIBILITY. WITH THE ATMOSPHERE DECOUPLING AT SUNSET...THE
RELAXING GRADIENT WILL ALLOW WINDS TO DROP BELOW LWA CRITERIA.
SUNDAY NIGHT/MONDAY...THE BASE OF THE TROUGH DROPS SOUTH INTO
NORTHERN COLORADO...TAKING MOST OF THE ENERGY TO OUR SOUTH.
HOWEVER THE INVERTED SURFACE EXTENDS NORTH INTO NORTHEASTERN
MONTANA WHICH WILL KEEP CONDITIONS A BIT UNSETTLED. WHILE
NAM...UKMET AND EC STAY DRY...BASED ON GFS...GEM AND SREF...SLIGHT
CHANCE POPS SEEM APPROPRIATE FOR SNOW OVERNIGHT. CONDITIONS DO
NOT CHANGE MUCH FOR MONDAY SO WILL KEEP SLIGHT CHANCE POPS GOING.
SURFACE HIGHS WILL DROP DOWN MUCH CLOSER TO NORMAL WHILE 850MB
TEMPERATURES HOVER AROUND -4*C. SO EXPECT ANY PRECIPITATION TO
FALL AS SNOW AND POSSIBLY RAIN SHOWERS. QPF AMOUNTS WILL NOT
PRODUCE ACCUMULATIONS. SCT
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
SHORTWAVE TROUGH DROPS SOUTHEAST OUT OF SASKATCHEWAN DURING THE
DAY TUESDAY AND MAY BRING A SLIGHT CHANCE OF RAIN OR SNOW. THIS
FAST MOVING SYSTEM WILL HAVE LIMITED MOISTURE WITH IT.
AN UPPER RIDGE BUILDS INTO THE AREA ON WEDNESDAY AND WILL BRING
WARM AND DRY WEATHER THROUGH THANKSGIVING DAY FOR SURE.
MODELS HAVE SOME DIFFERENCES ON TRACK OF A SHORTWAVE THAT MOVES
INLAND FROM THE PACIFIC ON FRIDAY. ECMWF TAKES THE SYSTEM SOUTH OF
THE AREA WHILE THE GFS BRINGS IT ACROSS MONTANA. EITHER WAY...A
COLD FRONT WILL AFFECT THE FORECAST AREA ON FRIDAY WITH COOLER
TEMPERATURES EXPECTED NEXT WEEKEND. WILL KEEP THE FORECAST DRY FOR
THE MOST PART FOR NOW. FORRESTER
&&
.AVIATION...
VFR CONDITIONS. A MIX OF MID AND HIGH LEVEL CLOUDS WILL MOVE
THROUGH THE AREA TODAY WITH SKIES CLEARING TONIGHT. SOUTHEAST
WINDS EARLY THIS MORNING WILL BECOME WEST AROUND 15Z AND INCREASE
TO 20 TO 25 KNOTS BY 18Z. THE WINDS WILL DIMINISH TO 10 TO 15
KNOTS THIS EVENING.
&&
.FIRE WEATHER...
A STRONG WEST WIND WILL DEVELOP TODAY BEHIND A COLD FRONT. WIND
SPEEDS ARE EXPECTED TO REACH 20 TO 30 MPH...WITH GUSTS TO 40 MPH
DURING THE LATE MORNING AND AFTERNOON HOURS. AFTERNOON MINIMUM
RELATIVE HUMIDITY VALUES ARE EXPECTED TO BRIEFLY DROP INTO THE 20
TO 30 PERCENT RANGE BEFORE BEGINNING A STEADY RECOVERY NEAR
SUNSET. THEREFORE...A BRIEF PERIOD OF CRITICAL FIRE WEATHER
CONDITIONS ARE POSSIBLE THIS AFTERNOON...BUT HIGHLIGHTS ARE NOT
EXPECTED AT THIS TIME DUE TO THE SHORT DURATION OF LOW RELATIVE
HUMIDITY DUE TO SHORTENING SUNLIGHT HOURS. THE MOST SUSCEPTIBLE
AREAS WILL BE THE LITTLE ROCKY MOUNTAINS AND THE MISSOURI BREAKS
REGION OF ZONES 119 AND 121...WHICH WILL EXPERIENCE A RATHER POOR
RELATIVE HUMIDITY RECOVERY LAST NIGHT. AJZ/SCT
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 10 AM THIS MORNING TO 5 PM MST THIS
AFTERNOON FOR FORT PECK LAKE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 210946
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
246 AM MST SAT NOV 21 2009
.SHORT TERM...VALID FOR TDY AND SUN...
PROGRESSIVE WEATHER PATTERN TO BE OVER THE FORECAST AREA THIS
WEEKEND AND INTO THE DAY MONDAY. LARGE TROUGH CURRENTLY MOVING
ONTO AND ACROSS THE PACIFIC NORTHWEST AND INTO THE NORTHERN
ROCKIES REGION. SATELLITE SHOWING A DEEP SOUTHWEST FLOW ALOFT
ACROSS THE STATE WITH PLENTY OF MID AND HIGH LEVEL CLOUDS MOVING
ACROSS OUR AREA. RADARS ACROSS IDAHO SHOWING CONVECTIVE TYPE
PRECIP NOW MOVING UP INTO THE SOUTHWEST PORTIONS OF THE STATE AND
APPROACHING OUR SOUTHWEST MOUNTAINS. A FEW LIGHTING STRIKES HAVE
ALSO BEEN OBSERVED ACROSS CENTRAL IDAHO INDICATING FAIRLY STRONG
DYNAMICS AND INSTABILITY FOR THIS TIME OF YEAR. WILL CONTINUE
WITH LIKELY POPS FOR THE SOUTHWEST MOUNTAINS WITH CHANCE POPS FOR
THE CENTRAL AND WESTERN ZONES THIS MORNING WITH BEST CHANCES
WEST. SNOWFALL COULD BE HEAVY FOR A SHORT WHILE OVER THE
BEARTOOTH/ABSAROKA MOUNTAINS RESULTING IN SEVERAL INCHES OF SNOW
THIS MORNING.
A COLD FRONT IS EXPECTED TO MOVE ACROSS THE CENTRAL AND WESTERN
PORTIONS OF THE FORECAST AREA BETWEEN 12-15Z AND THE EASTERN ZONES
BY EARLY AFTERNOON. DYNAMICS AND MOISTURE DECREASE BEHIND THE
FRONT RESULTING IN ONLY CHANCE POPS OVER THE MOUNTAINS...WITH
SLIGHT CHANCES SPREADING EAST DURING THE AFTERNOON. EXPECT WINDY
CONDITIONS TO DEVELOP BEHIND THE FRONT ACROSS THE PLAINS. THIS
DOWNSLOPE FLOW WILL HELP TO INHIBIT PRECIP ACROSS THE PLAINS.
DYNAMICS ALSO LOOK TO WEAKEN AS THE TROUGH MOVES ACROSS THE
FORECAST AREA SO FOR NOW WILL CONTINUE WITH ONLY A SLIGHT CHANCE
FOR SHOWERS ACROSS THE PLAINS TODAY.
RIDGING QUICKLY MOVES ACROSS THE CENTRAL PORTIONS OF THE STATE
TONIGHT BRINGING AN END TO ANY SHOWER ACTIVITY. HOWEVER...LEE-
SIDE TROUGHING DEVELOPS ACROSS THE FORECAST AREA LATE TONIGHT IN
ADVANCE OF THE NEXT FAST MOVING TROUGH ACROSS THE PACIFIC
NORTHWEST. PRESSURE GRADIENTS TIGHTEN ONCE AGAIN ACROSS THE
UPPER YELLOWSTONE AND STILLWATER VALLEYS LATE TONIGHT THROUGH
SUNDAY MORNING. AS A RESULT...HAVE PUT SUB-ADVISORY WINDS ACROSS
THESE AREAS FOR THIS TIME. ANOTHER COLD FRONT MOVES THROUGH LATE
SUNDAY MORNING WHICH WILL SHUT THE STRONGER WINDS OFF IN THE
LIVINGSTON AREA. THE GFS CONTINUES TO SHIFT THE BULK OF PRECIP
SOUTH ACROSS WESTERN WYOMING SO WILL CONTINUE WITH JUST A SLIGHT
CHANCE TO CHANCE POPS FOR OUR PLAINS WITH LIKELY POPS RETURNING
FOR THE MOUNTAINS. TEMPERATURES TODAY WILL BE COOLER BUT STILL
REMAIN ABOVE NORMAL BEFORE MORE NORMAL TEMPERATURES ARRIVE FOR
SUNDAY WITH READINGS IN THE UPPER 30S TO LOWER 40S. HOOLEY
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
A PROGRESSIVE PATTERN DEVELOPS OVER THE FORECAST AREA FOR THE
EXTENDED. 3 SYSTEMS WILL IMPACT THE AREA NEXT WEEK...BUT
RIDGING ON THANKSGIVING BRINGS WARM...DRY AND BREEZY CONDITIONS TO
THE AREA. THE FIRST SYSTEM IS OVER THE AREA MONDAY...SHIFTING
SOUTHEAST MONDAY NIGHT. INCREASED POPS OVER EASTERN AREAS MONDAY
AS WELL AS KEEPING SOME POPS FOR WESTERN MOUNTAIN AND FOOTHILLS
LOCATIONS. TEMPERATURES DON`T LOOK TERRIBLY COLD WITH THIS SYSTEM
IN THE LOWER 40S...AND COULD BE A TAD COOLER IN SOME LOCATIONS
WHERE CLOUDS AND PRECIPITATION OCCUR. AN ALBERTA CLIPPER SYSTEM
QUICKLY MOVES THROUGH EASTERN AREAS ON TUESDAY AFTERNOON...THOUGH
NOT BEFORE TEMPERATURES CLIMB INTO THE LOW TO MID 40S. IF TIMING
OF THE CLIPPER IS FASTER WILL NEED TO COOL EASTERN AREAS 5 TO 10
DEGREES. RIDGING BUILDS INTO THE AREA WEDNESDAY AND THURSDAY WITH
DOWNSLOPE WIND GRADIENT IN PLACE PUSHING TEMPERATURES BACK INTO
THE 50S. THE FINAL SYSTEM ARRIVES FRIDAY OR SATURDAY DEPENDING ON
MODEL PREFERENCE. THE ECMWF DIGS THE LATE WEEK SYSTEM FURTHER TO
THE SOUTH AND BRINGS COOLER AIR INTO THE AREA FRIDAY
AFTERNOON...WHILE THE GFS IS LESS DEEP WITH THE SYSTEM KEEPING THE
ENERGY OVER MONTANA AND WYOMING AND BRINGS COLDER AIR IN FOR
SATURDAY. 00Z ENSEMBLE DATA SUPPORTIVE OF THE OPERATIONAL GFS
KEEPING TROF FURTHER NORTH...AND TRENDED FORECAST TOWARD THE GFS
FOR THE LATER PERIODS...INCLUDING INCREASING POPS AND LOWERING
TEMPERATURES JUST A TAD. CHAMBERS
&&
.AVIATION...
A COLD FRONT WILL MOVE THROUGH THE AREA THIS MORNING. MVFR WITH
OCCASIONAL IFR CONDITIONS WILL DEVELOP EARLY THIS MORNING OVER
WESTERN AREAS...INCLUDING KLVM...LASTING INTO EARLY AFTERNOON. AS
THE FRONT MOVES EASTWARD CONDITIONS SHOULD REMAIN PRIMARILY VFR
WITH LOCAL MVFR CONDITIONS ASSOCIATED WITH ISOLATED SHOWER
ACTIVITY. MOUNTAIN OBSCURATION WILL LAST INTO LATE AFTERNOON FOR
WESTERN MOUNTAINS...AND INTO THIS EVENING FOR THE BIG HORN
MOUNTAINS...AS CONDITIONS IMPROVE FROM WEST TO EAST. GUSTY
NORTHWEST WINDS ARE EXPECTED ACROSS THE AREA BEHIND THE FRONT THIS
AFTERNOON. CHAMBERS
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 048 023/040 028/042 024/046 030/051 036/055 035/051
2/W 02/W 21/B 11/B 00/B 00/U 02/W
LVM 041 020/036 020/035 018/043 025/050 029/054 031/046
4/J 04/J 32/J 12/W 10/B 00/B 03/W
HDN 051 024/043 024/044 019/047 025/052 031/057 030/053
2/W 02/W 22/W 12/W 00/B 00/U 02/W
MLS 053 022/045 024/043 020/047 023/046 030/056 031/051
1/N 02/W 22/W 22/W 10/B 00/U 01/U
4BQ 051 023/042 021/042 019/045 022/046 028/056 029/051
1/N 22/W 22/J 12/W 00/B 00/U 01/U
BHK 053 021/045 021/040 019/043 020/040 024/054 027/051
1/N 11/B 22/J 22/W 10/B 00/U 01/U
SHR 047 020/043 022/039 014/046 024/050 028/056 028/051
3/W 22/W 22/J 11/B 00/B 00/U 01/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 210544
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 PM MST FRI NOV 20 2009
UPDATED AVIATION SECTION
.UPDATE...
PROGRESSION OF SHORTWAVE TROUGH SEEMS TO HAVE SLOWED A BIT MORE SO
HAVE LOWERED OVERNIGHT POPS ALONG THE CONTINENTAL DIVIDE AND
PORTIONS OF CENTRAL MONTANA. WEAK COLD FRONT STILL EXPECTED TO
PUSH THROUGH THE AREA OVERNIGHT...WITH TEMPERATURES FALLING CLOSER
TO SEASONAL AVERAGES ON SATURDAY. LIGHT SNOW WILL DEVELOP ALONG
THE CONTINENTAL DIVIDE AFTER MIDNIGHT WITH LIGHT SNOW ACCUMULATION
OF 1 TO 2 INCHES POSSIBLE. GUSTY WINDS AND FALLING SNOW MAY CAUSE
TIMES OF REDUCED VISIBILITIES ALONG THE MOUNTAIN PASSES. MLS
&&
.AVIATION...
UPDATED 0600Z.
AN UPPER LEVEL TROF OF LOW PRESSURE WILL MOVE EASTWARD TOWARDS
CENTRAL/SOUTHWEST MONTANA LATE TONIGHT. EXPECT GENERALLY OVERCAST
CONDITIONS UNTIL 00Z SUNDAY...WITH THE CHANCE FOR SNOW DEVELOPING
AFTER 09Z OVER WESTERN AND SOUTHWESTERN MONTANA. THE BEST CHANCE FOR
SNOW ON SATURDAY WILL BE ON SATURDAY FROM 13Z TO 20Z IN THE BOZEMAN
AND WEST YELLOWSTONE AREA. THUS IFR/LIFR CONDITIONS WILL BE POSSIBLE
AT TIMES OVER THIS REGION. MOUNTAINS WILL BE OBSCURED AT TIMES
THROUGHOUT THE REGION THOUGH THE PERIOD. ADDITIONALLY...EXPECT
SURFACE WINDS TO BECOME VERY BREEZY OVER NORTH CENTRAL MONTANA AFTER
09Z SATURDAY. EXPECT A GENERALLY CLEARING TREND WITH LIGHTER WINDS
EXPECTED FROM 0Z SUNDAY UNTIL 6Z SUNDAY. BRUSDA
&&
.PREV DISCUSSION...
/ISSUED 500 PM MST FRI NOV 20 2009/
AN UPPER LEVEL TROUGH OF LOW PRESSURE...CURRENTLY MOVING ONTO THE
WEST COAST...WILL TRACK EAST ACROSS THE REGION LATE TONIGHT
THROUGH EARLY SATURDAY AFTERNOON. A BRIEF PERIOD OF RIDGING BEHIND
THIS INITIAL SYSTEM SATURDAY NIGHT WILL BE QUICKLY FOLLOWED BY
ANOTHER TROUGH MOVING INTO THE NORTHERN ROCKIES ON SUNDAY. A COLD
FRONT ASSOCIATED WITH THE INITIAL TROUGH WILL MOVE EAST ACROSS THE
REGION LATE TONIGHT. MOISTURE WILL INCREASE ALONG AND BEHIND THE
FRONT WITH SNOW SHOWERS DEVELOPING AFTER MIDNIGHT OVER THE ROCKY
MTN FRONT AND GLACIER PARK AREA...SPREADING EAST OVER SW MT LATE
TONIGHT THROUGH SATURDAY MORNING. WESTERLY DOWNSLOPE FLOW WILL
LIMIT PRECIPITATION CHANCES OVER THE PLAINS...HOWEVER OCCASIONAL
SNOW SHOWERS OVER THE MTNS MAY BRING ACCUMULATIONS OF 1 TO 3
INCHES TO ELEVATIONS ABOVE 6000 FT. SIGNIFICANT COOLING WILL OCCUR
BEHIND THE FRONT OVER THE FORECAST AREA ON SATURDAY...HOWEVER THIS
WILL ONLY MEAN TEMPERATURES DROPPING BACK TO SEASONAL AVERAGES.
MODELS HAVE BEEN TRENDING SLOWER AND DEEPER WITH THE SECOND SYSTEM
TO ARRIVE ON SUNDAY AND THIS SYSTEM WILL LIKELY BRING ANOTHER
ROUND OF SNOW SHOWERS TO THE MTNS WITH PERHAPS A LITTLE BETTER
CHANCE OF SNOW SHOWERS EXTENDING FARTHER EAST ONTO THE PLAINS DUE
TO DEEPER MOISTURE AND MARGINAL INSTABILITY. ACCUMULATING SNOW
AGAIN LOOKS TO BE CONFINED MAINLY TO THE MOUNTAINOUS AREAS WITH
ANOTHER 1 TO 3 INCHES POSSIBLE ABOVE 6000 FEET. GUSTY SOUTHWEST
WINDS WILL SHIFT TO THE WEST BEHIND TONIGHTS COLD COLD FRONT WITH
WESTERN PORTIONS OF NORTH CENTRAL MT AND MTN PASSES SEEING THE
STRONGEST WINDS WITH GUSTY WINDS CONTINUING THROUGH THE WEEKEND.
COMBINATION OF GUSTY WINDS AND PERIODS OF LIGHT SNOW MAY HAVE AN
IMPACT TO TRAVELERS OVER MTN PASSES THIS WEEKEND AND WILL
HIGHLIGHT THIS IN THE HAZARDOUS WEATHER OUTLOOK. HOENISCH
SUNDAY NIGHT THROUGH FRIDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT WITH MOVING THE UPPER LEVEL TROUGH OUT OF THE AREA
SUNDAY NIGHT INTO MONDAY FOR A DECREASING CHANCE OF PRECIPITATION.
AS THE COLD FRONT ASSOCIATED WITH THIS SYSTEM ALSO MOVES THROUGH THE
AREA SUNDAY NIGHT...WEST WINDS WILL BECOME BREEZY AND GUSTY. THESE
WINDS WILL DECREASE ON MONDAY AS THE FRONT EXITS THE AREA TO THE
EAST...AS TEMPERATURES CONTINUE TO HOVER AROUND NORMAL. THE UPPER
LEVEL HIGH PRESSURE RIDGE OVER THE EASTERN PACIFIC WILL THEN BEGIN
TO BUILD BACK INTO THE WESTERN UNITED STATES MONDAY NIGHT THROUGH
TUESDAY NIGHT. HOWEVER...A WEAK SHORTWAVE WILL MOVE DOWN THE EAST
SIDE OF THE RIDGE AND THROUGH MONTANA DURING THIS TIME. THIS WILL
BRING A CHANCE OF PRECIPITATION TO THE AREA ONCE AGAIN...BUT IT WILL
MAINLY BE IN THE MOUNTAINS AS WESTERLY DOWNSLOPE WINDS WILL INCREASE
WITH THE PASSAGE OF THE SHORTWAVE. THESE WINDS WILL ALSO WARM
TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE NORMAL ON TUESDAY. THE
UPPER LEVEL RIDGE WILL THEN BUILD INTO MONTANA TUESDAY NIGHT THROUGH
THURSDAY (THANKSGIVING DAY)...WHICH WILL KEEP ONLY A SLIGHT CHANCE
OF PRECIPITATION IN THE WESTERN MONTANA MOUNTAINS. ALSO...WESTERLY
DOWNSLOPE WINDS WILL INCREASE ONCE AGAIN THROUGH THIS PERIOD...WHICH
WILL KEEP TEMPERATURES ABOUT 10 DEGREES ABOVE NORMAL. THE MODELS
BEGIN TO DIVERGE FOR THE REMAINDER OF THIS FORECAST PERIOD. THE GFS
IS MUCH FASTER THAN THE ECMWF WITH BRINGING THE NEXT PACIFIC WEATHER
SYSTEM THROUGH THE AREA. THE GFS MOVES IT THROUGH MONTANA ON
FRIDAY...WHILE THE ECMWF IS 12 TO 24 HOURS SLOWER IN MOVING IT
THROUGH FRIDAY NIGHT INTO SATURDAY. WITH THIS UNCERTAINTY...HAVE
GONE WITH A WIDESPREAD CHANCE OF PRECIPITATION FOR FRIDAY AND FRIDAY
NIGHT...WITH THE CHANCE BEING HIGHER THAN CLIMATOLOGICAL AVERAGES.
HAVE ALSO COOLED TEMPERATURES CLOSER TO NORMAL. THE INCREASES IN WIND
SUNDAY NIGHT...MONDAY NIGHT AND TUESDAY...AND THANKSGIVING DAY
INTO FRIDAY WILL NEED TO BE MONITORED FOR POSSIBLE HIGHLIGHTS.
COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 36 42 25 41 / 0 10 0 30
CTB 31 40 24 39 / 10 10 0 20
HLN 29 41 23 41 / 20 20 0 40
BZN 23 37 13 37 / 20 50 0 40
WEY 22 29 8 30 / 50 90 30 90
DLN 27 32 14 34 / 40 50 0 50
HVR 29 49 21 45 / 0 10 10 20
LWT 32 42 20 38 / 0 10 0 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
000
FXUS65 KTFX 210446
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
946 PM MST FRI NOV 20 2009
.UPDATE...
PROGRESSION OF SHORTWAVE TROUGH SEEMS TO HAVE SLOWED A BIT MORE SO
HAVE LOWERED OVERNIGHT POPS ALONG THE CONTINENTAL DIVIDE AND
PORTIONS OF CENTRAL MONTANA. WEAK COLD FRONT STILL EXPECTED TO
PUSH THROUGH THE AREA OVERNIGHT...WITH TEMPERATURES FALLING CLOSER
TO SEASONAL AVERAGES ON SATURDAY. LIGHT SNOW WILL DEVELOP ALONG
THE CONTINENTAL DIVIDE AFTER MIDNIGHT WITH LIGHT SNOW ACCUMULATION
OF 1 TO 2 INCHES POSSIBLE. GUSTY WINDS AND FALLING SNOW MAY CAUSE
TIMES OF REDUCED VISIBILITIES ALONG THE MOUNTAIN PASSES. MLS
&&
.AVIATION...
UPDATED 0000Z.
AN UPPER LEVEL TROF OF LOW PRESSURE WILL MOVE EASTWARD TOWARDS
CENTRAL/SOUTHWEST MONTANA LATE TONIGHT. EXPECT GENERALLY OVERCAST
CONDITIONS THROUGH THE PERIOD...WITH THE CHANCE FOR SNOW DEVELOPING
AFTER 09Z OVER WESTERN AND SOUTHWESTERN MONTANA. THE BEST CHANCE FOR
SNOW ON SATURDAY WILL BE ON SATURDAY FROM 14Z TO 20Z IN THE BOZEMAN
AND WEST YELLOWSTONE AREA. THUS IFR/LIFR CONDITIONS WILL BE POSSIBLE
AT TIMES OVER THIS REGION. MOUNTAINS WILL BE OBSCURED AT TIMES
THROUGHOUT THE REGION THOUGH THE PERIOD. ADDITIONALLY...EXPECT
SURFACE WINDS TO BECOME VERY BREEZY OVER NORTH CENTRAL MONTANA AFTER
09Z SATURDAY. BRUSDA
&&
.PREV DISCUSSION...
/ISSUED 500 PM MST FRI NOV 20 2009/
AN UPPER LEVEL TROUGH OF LOW PRESSURE...CURRENTLY MOVING ONTO THE
WEST COAST...WILL TRACK EAST ACROSS THE REGION LATE TONIGHT
THROUGH EARLY SATURDAY AFTERNOON. A BRIEF PERIOD OF RIDGING BEHIND
THIS INITIAL SYSTEM SATURDAY NIGHT WILL BE QUICKLY FOLLOWED BY
ANOTHER TROUGH MOVING INTO THE NORTHERN ROCKIES ON SUNDAY. A COLD
FRONT ASSOCIATED WITH THE INITIAL TROUGH WILL MOVE EAST ACROSS THE
REGION LATE TONIGHT. MOISTURE WILL INCREASE ALONG AND BEHIND THE
FRONT WITH SNOW SHOWERS DEVELOPING AFTER MIDNIGHT OVER THE ROCKY
MTN FRONT AND GLACIER PARK AREA...SPREADING EAST OVER SW MT LATE
TONIGHT THROUGH SATURDAY MORNING. WESTERLY DOWNSLOPE FLOW WILL
LIMIT PRECIPITATION CHANCES OVER THE PLAINS...HOWEVER OCCASIONAL
SNOW SHOWERS OVER THE MTNS MAY BRING ACCUMULATIONS OF 1 TO 3
INCHES TO ELEVATIONS ABOVE 6000 FT. SIGNIFICANT COOLING WILL OCCUR
BEHIND THE FRONT OVER THE FORECAST AREA ON SATURDAY...HOWEVER THIS
WILL ONLY MEAN TEMPERATURES DROPPING BACK TO SEASONAL AVERAGES.
MODELS HAVE BEEN TRENDING SLOWER AND DEEPER WITH THE SECOND SYSTEM
TO ARRIVE ON SUNDAY AND THIS SYSTEM WILL LIKELY BRING ANOTHER
ROUND OF SNOW SHOWERS TO THE MTNS WITH PERHAPS A LITTLE BETTER
CHANCE OF SNOW SHOWERS EXTENDING FARTHER EAST ONTO THE PLAINS DUE
TO DEEPER MOISTURE AND MARGINAL INSTABILITY. ACCUMULATING SNOW
AGAIN LOOKS TO BE CONFINED MAINLY TO THE MOUNTAINOUS AREAS WITH
ANOTHER 1 TO 3 INCHES POSSIBLE ABOVE 6000 FEET. GUSTY SOUTHWEST
WINDS WILL SHIFT TO THE WEST BEHIND TONIGHTS COLD COLD FRONT WITH
WESTERN PORTIONS OF NORTH CENTRAL MT AND MTN PASSES SEEING THE
STRONGEST WINDS WITH GUSTY WINDS CONTINUING THROUGH THE WEEKEND.
COMBINATION OF GUSTY WINDS AND PERIODS OF LIGHT SNOW MAY HAVE AN
IMPACT TO TRAVELERS OVER MTN PASSES THIS WEEKEND AND WILL
HIGHLIGHT THIS IN THE HAZARDOUS WEATHER OUTLOOK. HOENISCH
SUNDAY NIGHT THROUGH FRIDAY NIGHT...THE MEDIUM RANGE MODELS ARE IN
DECENT AGREEMENT WITH MOVING THE UPPER LEVEL TROUGH OUT OF THE AREA
SUNDAY NIGHT INTO MONDAY FOR A DECREASING CHANCE OF PRECIPITATION.
AS THE COLD FRONT ASSOCIATED WITH THIS SYSTEM ALSO MOVES THROUGH THE
AREA SUNDAY NIGHT...WEST WINDS WILL BECOME BREEZY AND GUSTY. THESE
WINDS WILL DECREASE ON MONDAY AS THE FRONT EXITS THE AREA TO THE
EAST...AS TEMPERATURES CONTINUE TO HOVER AROUND NORMAL. THE UPPER
LEVEL HIGH PRESSURE RIDGE OVER THE EASTERN PACIFIC WILL THEN BEGIN
TO BUILD BACK INTO THE WESTERN UNITED STATES MONDAY NIGHT THROUGH
TUESDAY NIGHT. HOWEVER...A WEAK SHORTWAVE WILL MOVE DOWN THE EAST
SIDE OF THE RIDGE AND THROUGH MONTANA DURING THIS TIME. THIS WILL
BRING A CHANCE OF PRECIPITATION TO THE AREA ONCE AGAIN...BUT IT WILL
MAINLY BE IN THE MOUNTAINS AS WESTERLY DOWNSLOPE WINDS WILL INCREASE
WITH THE PASSAGE OF THE SHORTWAVE. THESE WINDS WILL ALSO WARM
TEMPERATURES TO ABOUT 5 TO 10 DEGREES ABOVE NORMAL ON TUESDAY. THE
UPPER LEVEL RIDGE WILL THEN BUILD INTO MONTANA TUESDAY NIGHT THROUGH
THURSDAY (THANKSGIVING DAY)...WHICH WILL KEEP ONLY A SLIGHT CHANCE
OF PRECIPITATION IN THE WESTERN MONTANA MOUNTAINS. ALSO...WESTERLY
DOWNSLOPE WINDS WILL INCREASE ONCE AGAIN THROUGH THIS PERIOD...WHICH
WILL KEEP TEMPERATURES ABOUT 10 DEGREES ABOVE NORMAL. THE MODELS
BEGIN TO DIVERGE FOR THE REMAINDER OF THIS FORECAST PERIOD. THE GFS
IS MUCH FASTER THAN THE ECMWF WITH BRINGING THE NEXT PACIFIC WEATHER
SYSTEM THROUGH THE AREA. THE GFS MOVES IT THROUGH MONTANA ON
FRIDAY...WHILE THE ECMWF IS 12 TO 24 HOURS SLOWER IN MOVING IT
THROUGH FRIDAY NIGHT INTO SATURDAY. WITH THIS UNCERTAINTY...HAVE
GONE WITH A WIDESPREAD CHANCE OF PRECIPITATION FOR FRIDAY AND FRIDAY
NIGHT...WITH THE CHANCE BEING HIGHER THAN CLIMATOLOGICAL AVERAGES.
HAVE ALSO COOLED TEMPERATURES CLOSER TO NORMAL. THE INCREASES IN WIND
SUNDAY NIGHT...MONDAY NIGHT AND TUESDAY...AND THANKSGIVING DAY
INTO FRIDAY WILL NEED TO BE MONITORED FOR POSSIBLE HIGHLIGHTS.
COULSTON
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 36 42 25 41 / 0 10 0 30
CTB 31 40 24 39 / 10 10 0 20
HLN 29 41 23 41 / 20 20 0 40
BZN 23 37 13 37 / 20 50 0 40
WEY 22 29 8 30 / 50 90 30 90
DLN 27 32 14 34 / 40 50 0 50
HVR 29 49 21 45 / 0 10 10 20
LWT 32 42 20 38 / 0 10 0 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
000
FXUS65 KGGW 210418 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
918 PM MST FRI NOV 20 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
THE UPPER LEVEL TROUGH...CURRENTLY SLAMMING INTO THE NORTHWEST
COAST...CONTINUES TO EJECT MOISTURE INTO THE SOUTHWEST FLOW OVER
THE DIVIDE WHICH IS PRODUCING OPAQUE HIGH CLOUDS ABOVE
NORTHEASTERN MONTANA THIS EVENING. ADJUSTED SKY COVER FARTHER TO
THE EAST.
A LEE SURFACE TROUGH WILL SLIDE EAST OVER THE ZONES TONIGHT WHICH
WILL BACK SOUTHERLY WINDS TO THE WEST BY MORNING. A SURFACE
GRADIENT OF INCREASING STRENGTH WILL MAINTAIN WINDS TONIGHT AT
10KT-15KT OVER FAVORED AREAS. MADE A FEW TWEAKS TO THE WIND GRIDS
BASED ON CURRENT OBSERVATIONS AND UPDATED GUIDANCE.
OTHERWISE CONDITIONS WILL STAY DRY SO FEW GRID CORRECTIONS ARE
NEEDED. SCT
PREVIOUS DISCUSSION...
AN UPPER TROUGH IS MOVING OVER THE WEST COAST THIS AFTERNOON WITH
AN UPPER RIDGE REMAINING OVER THE NORTHERN HIGH PLAINS. A COPIOUS
AMOUNT OF UPPER LEVEL PACIFIC MOISTURE IS SPILLING OVER THE
CONTINENTAL DIVIDE RESULTING IN AN EXTENSIVE AREA OF DENSE CIRRUS
CLOUDS. THE OPAQUENESS OF THIS CIRRUS HAS GENERALLY HELD
TEMPERATURES BELOW FORECAST VALUES...BUT NEVERTHELESS STILL VERY
MILD FOR THE LATER HALF OF NOVEMBER.
THE TROUGH WILL CONTINUE ITS PROGRESSION EAST TONIGHT WITH HIGH
CLOUDS CONTINUING TO STREAM OVERHEAD. LOW TEMPERATURES WILL BE ON
THE MILD SIDE...WITH A FEW OF THE LOW LYING AREAS EXPERIENCING
COLD AIR DRAINAGE AS THE WIND BECOMES LIGHT. A PACIFIC COLD FRONT
ASSOCIATED WITH THE TROUGH WILL MOVE THROUGH SATURDAY MORNING WITH
A STRONG WEST WIND DEVELOPING DURING THE LATE MORNING AND
CONTINUING THROUGH THE AFTERNOON. COLD AIR ADVECTION AND
SUBSIDENCE SHOULD SUSTAIN THE SURFACE WIND ALONG WITH STRONGER
GUSTS AS 850MB WIND SPEEDS REACH NEAR 35KT. AFTERNOON RELATIVE
HUMIDITY VALUES COULD BE RATHER LOW WITH A DOWNSLOPING WESTERLY
WIND. A SHORT PERIOD OF NEAR CRITICAL FIRE WEATHER CONDITIONS ARE
POSSIBLE. SEE THE FIRE WEATHER DISCUSSION BELOW FOR MORE
INFORMATION. THE WIND SPEED WILL EASILY MEET LAKE WIND ADVISORY
CRITERIA...SO ONE WILL BE ISSUED FOR FORT PECK LAKE.
A SHORTWAVE RIDGE CROSSES THE NORTHERN PRAIRIE SATURDAY NIGHT AND
EARLY SUNDAY BRINGING AN END TO THE WIND AND LESS CLOUD COVER. LOW
TEMPERATURES SATURDAY NIGHT COULD APPROACH SEASONAL AVERAGES UNDER
A MOSTLY CLEAR SKY. A SHORTWAVE TROUGH QUICKLY ARRIVES SUNDAY
AFTERNOON. A FEW AREAS OF LIGHT RAIN ARE POSSIBLE IN THE
AFTERNOON. SURFACE TEMPERATURES APPEAR TOO WARM FOR ANY SNOW
DURING THE AFTERNOON. AJZ
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
NO SIGNIFICANT CHANGES IN THE LONG TERM PERIOD. SEVERAL WEAK
SHORTWAVE TROFS MOVE THROUGH THE REGION...ONE SUNDAY NIGHT WITH
ANOTHER ON TUESDAY. SOME POTENTIAL FOR PRECIPITATION WITH EITHER
OF THE WAVES SO KEPT THE LOW POPS FOR THOSE PERIODS. OTHERWISE
WITH THE MORE PROGRESSIVE FLOW TEMPERATURES WILL BE CLOSER TO
NORMAL BUT STILL WARM FOR LATE NOVEMBER.
PREVIOUS LONG TERM DISCUSSION....AN UPPER SHORT-WAVE TROUGH
SWINGS THROUGH EASTERN MONTANA SUNDAY NIGHT BUT APPEARS TO KEEP
MOST ENERGY TO OUR SOUTH. THE COLD FRONT IS RATHER SUBTLE SO DO
NOT EXPECT MUCH IN THE WAY OF QPF...BUT CANNOT RULE IT OUT EITHER.
WITH 850MB TEMPERATURES AT -2*C TO -4*C ANY PRECIPITATION THAT
DOES DEVELOP WILL LIKELY BE SNOW. THE GFS AND EC DO NOT BEGIN IN
PHASE...WITH THE GFS AROUND 6-HOURS AHEAD OF THE EC. SO WILL KEEP
12-HOURS POP/WX GRIDS. THE GEM ALSO FAVORS KEEPING MOST QPF TO OUR
SOUTH BUT SUPPORTS LOW POPS FOR OUR AREA. THE PHASE DIFFERENCE
BETWEEN GFS AND EC BECOMES MORE PRONOUNCED DURING THE REMAINDER OF
THE EXTENDED PERIOD AS THE MODELS BECOME MORE PROGRESSIVE.
MONDAY/MONDAY NIGHT...THE TROUGH MOVES TO THE EAST AS AN UPPER
RIDGE/WARM FRONT MOVES OVER THE WEST. THE RIDGE WILL LIKELY BE
SHORT LIVED SINCE MODELS SHOW ANOTHER SHORT WAVE TROUGH
APPROACHING. THE GEM IS SLOWER TO EXIT ANY PRECIPITATION SO WILL
MODIFY POPS BASED ON THE UNCERTAINTY.
TUESDAY/TUESDAY NIGHT...THE 00Z GFS AND 12Z EC AGREE WITH THE
SHORT-WAVE AFFECTING THE AREA BUT DIFFER QUITE A BIT ON LOCATION
AND TIMING. THE GFS BRINGS IN THE MOISTURE DURING THE DAY WHILE
THE EC PREFERS TUESDAY NIGHT. THE 00Z EC WHICH CAME IN DURING THE
SHIFT KEPT THE MOISTURE SOUTH OF THE AREA. THE GEM BY NOW APPEARS
TO BE ON A DIFFERENT PLANET...SO WILL DISREGARD. AGAIN ANY
PRECIPITATION THAT DEVELOPS WILL LIKELY BE LIGHT AND IN THE FORM
OF SNOW OR A MIX WITH MOST 850MB TEMPERATURES NEAR OR BELOW 0*C.
SURFACE TEMPERATURES WILL LIKELY DROP MUCH CLOSER TO NORMAL.
WEDNESDAY AND BEYOND...UPPER RIDGING APPEARS TO FOLLOW...ALTHOUGH
ENSEMBLE AND OPERATIONAL PHASING AND AMPLITUDE VARY GREATLY
BETWEEN GFS AND EC. SURFACE TEMPERATURES ARE EXPECTED TO ONCE
AGAIN RISE ABOVE NORMAL...BY AROUND 10*F TO 15*F. THE NEXT SHORT
WAVE TROUGH CRASHES INTO THE NORTHWEST COAST AROUND THURSDAY...BUT
THERE CONTINUES TO BE NO CONSENSUS AS TO HOW THE TROUGH DEVELOPS
AND AFFECTS NORTHEAST MONTANA. SCT
&&
.AVIATION...
VFR CONDITIONS. SCATTERED TO BROKEN HIGH CLOUDS WILL GIVE WAY TO
INCREASING MID-LEVEL CLOUDS LATE TONIGHT AS A COLD FRONT
APPROACHES THE AREA. EAST TO SOUTHEAST WINDS OVERNIGHT WILL TURN
NORTHWEST AND INCREASE BEHIND THE FRONTAL PASSAGE DURING THE LATE
MORNING. RAE
&&
.FIRE WEATHER...
A STRONG WEST WIND WILL DEVELOP SATURDAY BEHIND A COLD FRONT.
WIND SPEEDS ARE EXPECTED TO REACH 20 TO 30 MPH...WITH GUSTS TO 40
MPH DURING THE LATE MORNING AND AFTERNOON HOURS. AFTERNOON
MINIMUM RELATIVE HUMIDITY VALUES ARE EXPECTED TO BRIEFLY DROP INTO
THE 20 TO 30 PERCENT RANGE BEFORE BEGINNING A STEADY RECOVERY NEAR
SUNSET. THEREFORE...A BRIEF PERIOD OF CRITICAL FIRE WEATHER
CONDITIONS ARE POSSIBLE SATURDAY AFTERNOON...BUT HIGHLIGHTS ARE
NOT EXPECTED AT THIS TIME DUE TO THE SHORT DURATION OF LOW
RELATIVE HUMIDITY. THE MOST SUSCEPTIBLE AREAS WILL BE THE LITTLE
ROCKY MOUNTAINS AND THE MISSOURI BREAKS REGION OF ZONES 119 AND
121...WHICH WILL EXPERIENCE A RATHER POOR RELATIVE HUMIDITY
RECOVERY TONIGHT. AJZ
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 10 AM TO 5 PM MST SATURDAY FOR FORT PECK
LAKE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 210349
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
849 PM MST FRI NOV 20 2009
.EVENING UPDATE...
FORECAST ON TRACK AND HAVE ONLY MADE A FEW MINOR ADJUSTMENTS.
SATELLITE SHOWING A LARGE TROUGH CURRENTLY MOVING ACROSS THE
PACIFIC NORTHWEST COAST AND INTO THE NORTHERN ROCKIES AREA. DEEP
SOUTHWEST FLOW ALOFT AHEAD OF THIS TROUGH IS BRINGING ABUNDANT
MID AND HIGH LEVEL CLOUDS ACROSS THE FORECAST AREA THIS EVENING.
AS A RESULT...HAVE INCREASED SKY COVER ACROSS THE AREA ESPECIALLY
THE EASTERN ZONES. MODELS HAVE SLOWED THE PROGRESSION OF THIS
TROUGH JUST A BIT WITH PRECIP NOT MAKING IT MUCH INTO OUR WESTERN
ZONES UNTIL VERY LATE TOWARD 12Z SATURDAY. AREA RADARS NOT
SHOWING ANY ACTIVITY APPROACHING AS WELL. HAVE THEREFORE TRIMMED
BACK POPS IN THE NORTHWEST AND WESTERN LOWER ELEVATION ZONES. DID
ALSO LOWER POP CHANCES JUST A BIT AS WELL FOR THE SOUTHWEST
MOUNTAINS. WINDS HAVE ALSO DECREASED QUITE A BIT IN THE
LIVINGSTON AREA SO HAVE LOWERED THESE FOR THE REMAINDER OF THE
NIGHT. TEMPERATURES ACROSS PORTIONS OF THE CENTRAL AND WEST
REMAIN IN THE 40S THIS EVENING. STILL EXPECT MIXING TO CONTINUE
THROUGHOUT THE NIGHT AND LATEST GUIDANCE COMING IN A BIT WARMER AS
WELL. SO HAVE BUMPED UP READINGS IN A FEW LOCATIONS. UPDATE OUT
SHORTLY. HOOLEY
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
WHILE THE FAIRLY BENIGN WEATHER PATTERN CONTINUES INTO THE
EXTENDED THE MODELS ARE NOT IN REAL STRONG AGREEMENT. ON MONDAY
ECMWF AND GFS ARE VERY DIFFERENT IN THE TRACK OF AN UPPER LOW
THROUGH THE AREA WITH THE ECMWF THE PREFERRED SOLUTION. GFS TRACKS
AN UPPER TROUGH ACROSS THE AREA WHILE THE ECMWF DIVES A SYSTEM
SOUTH THROUGH WYOMING. GFS HINTS AT SOME WRAP AROUND PRECIPITATION
AS THE SYSTEM AND GFS HAS BEEN TRENDING UPWARD WITH POPS SO HAVE
KEPT SOME POPS IN SOUTHEAST MONTANA AS A HEDGE...BUT GENERALLY
PREFER ECMWF SOLUTION. WILL CONTINUE COOL UNDER NORTHERLY FLOW
ALOFT THE REMAINDER OF THE DAY. TUESDAY MODELS CONTINUE TO
DISAGREE WITH A ANOTHER WAVE COMING THROUGH THE NORTHWEST FLOW
AND AMPLIFYING IT ON THE GFS WHILE THE ECMWF HAS A LIGHTER ZONAL
FLOW. SINCE THE ECMWF IS DOING A BETTER JOB OF CUTTING OFF THE
SYSTEM OVER THE PLAINS WHICH HAS BEEN THE TREND AS OF LATE. LOOKS
DRY EITHER WAY AND DO NOT STRENGTHEN WINDS AS MUCH AS GFS WOULD
INDICATE. BOTH MODELS BRING AN UPPER LEVEL RIDGE INTO THE AREA FOR
WEDNESDAY AND THURSDAY FOR TEMPERATURES 10 TO 15 DEGREES ABOVE
NORMAL AND A DOWNSLOPING WIND PATTERN. RIDGE BREAKS DOWN ON BOTH
MODELS FOR FRIDAY AND THE WEEKEND BUT AGAIN MODELS DISAGREE ON
TRACKS OF SYSTEM THROUGH THE REGION. DEFINITELY COOLER AS THE
TRANSITION OCCURS BUT NOT REALLY SURE ABOUT PRECIPITATION AT THIS
POINT. BORSUM
&&
.AVIATION...
RAIN AND SNOW SHOWERS ARE EXPECTED IN AND AROUND KLVM AND IN THE
HIGH TERRAIN BY AROUND MIDNIGHT...AS A COLD FRONT PUSHES FROM WEST
TO EAST ACROSS THE REGION OVERNIGHT. MAINLY VFR FLIGHT CONDITIONS
CAN BE EXPECTED TO PREVAIL OVER THE PLAINS. EXPECT INCREASING
CLOUDINESS OVER THE MOUNTAINS AND FOOTHILL REGION...WITH CEILINGS
DROPPING TO MVFR LEVELS AFTER MIDNIGHT. MOUNTAIN OBSCURATIONS AND
LOWER CEILINGS WILL CONTINUE THROUGH TOMORROW AFTERNOON. GILSTAD
&&
.PRELIMINARY POINT TEMP/POPS...
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 034/046 024/041 026/041 025/044 026/050 031/052 031/053
03/W 02/O 22/S 11/N 10/B 00/B 01/N
LVM 031/041 022/037 018/037 024/041 025/048 030/051 029/047
24/J 04/S 31/B 12/S 10/B 00/N 02/R
HDN 028/051 024/043 024/045 023/048 023/051 023/052 024/053
02/W 02/O 22/S 12/S 20/B 00/B 01/B
MLS 026/050 024/046 024/044 021/045 022/048 025/052 027/052
02/W 02/O 21/B 12/S 20/B 00/B 01/B
4BQ 027/051 023/042 021/041 021/046 021/044 025/049 025/050
02/W 22/O 22/S 12/S 21/B 00/B 01/B
BHK 026/054 024/044 021/040 018/041 020/042 023/051 024/051
02/W 20/B 22/S 12/S 21/B 00/B 01/B
SHR 029/047 019/043 020/040 018/047 019/047 022/050 021/049
03/W 22/O 22/S 12/S 20/B 00/B 01/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KMSO 210309
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
809 PM MST FRI NOV 20 2009
.UPDATE...UPDATED EARLIER TONIGHT TO LOWER THE POPS ACROSS
NORTHWEST MONTANA FROM 00Z TO 03Z. ALSO LOWERED SOME MIN
TEMPERATURES TONIGHT.
&&
.DISCUSSION...MODELS ARE SLOWER AT BRINGING THE SYSTEM INTO
WESTERN MONTANA AND NORTH CENTRAL IDAHO TONIGHT. IN
ADDITION...SATELLITE IMAGERY AND RADARS TO OUR WEST HAS SHOWN THAT
THE SYSTEM IS MOVING SLOWER THEN EARLIER EXPECTED. SO UPDATED THE
POPS AND WEATHER FOR TONIGHT TO SHOW THE SLOWER TREND. SOME
LOCATIONS WERE AT THE FORECASTED LOW TEMPERATURE FOR TONIGHT AND
OTHERS WERE WITHIN A COUPLE OF DEGREES. MOST LOCATIONS FROM
MISSOULA NORTH NEVER WARMER UP TODAY...WITH OBSERVED HIGHS ABOUT
6 DEGREES BELOW NUMERIC GUIDANCE. SO LOWERED A NUMBER OF LOCATIONS
MAINLY ACROSS NORTHWEST MONTANA. REST OF THE FORECAST LOOKS TO BE
ON TRACK. WILL CONTINUE THE WINTER WEATHER ADVISORY FOR IDZ005-006
&&
.AVIATION...AN APPROACHING PACIFIC SYSTEM WILL CONTINUE TO
LOWER CLOUDS DECKS AND INCREASE PRECIPITATION CHANCES ACROSS THE
NORTHERN ROCKIES OVERNIGHT. AHEAD OF THE ADVANCING SURFACE COLD
FRONT...SHOWERS WILL BE A MIX OF RAIN AND SNOW BEFORE TURNING TO
ALL SNOW AFTER 21/0600Z. EXPECT THE MOST INTENSE PERIODS OF
PRECIPITATION ALONG AND JUST BEHIND THE FRONTAL PASSAGE BETWEEN
21/0600Z-21/1200Z. CEILINGS ARE EXPECTED TO LOWER OVERNIGHT
CAUSING MOUNTAINS AND PASSES TO BE OBSCURED.
&&
.PREV DISCUSSION... /ISSUED 301 PM MST FRI NOV 20 2009/
DISCUSSION...COMPLEX WEATHER PATTERN SETTING UP OVER THE
INTERMOUNTAIN REGION FOR THIS WEEKEND. BEEN AN INTERESTING DAY AS
CLOUDS AHEAD OF APPROACHING SYSTEM WERE QUITE MORE INTENSE THAN
THE MODELS HAD ADVERTISED. AS A RESULT...THE WARMING EXPECTED
TODAY WAS LIMITED TO THE SOUTHERN MOST VALLEYS (HIGHER VALLEYS)
THAT MIXED OUT EARLIER THIS MORNING AND ACHIEVED FULL MIXING
DESPITE THE CLOUDS. CENTRAL AND NORTHERN MONTANA VALLEYS WERE
INHIBITED BY THESE CLOUDS AND KEPT THE MUCH COOLER TEMPERATURES
TRAPPED IN THEIR VALLEYS. EXAMPLE...MISSOULA 37 DEGREES...HAMILTON
54 AT 230 PM MST.
THE AFOREMENTIONED WEATHER SYSTEM WILL MOVE OVER THE PACIFIC
NORTHWEST THIS EVENING SPREADING PRECIPITATION FROM WEST TO EAST
THIS EVENING AND OVERNIGHT. WARM AIR AHEAD OF THE COLD FRONT WILL
KEEP SNOW LEVELS RATHER HIGH...THEN DROPPING TO MOST VALLEY FLOORS
AFTER THE COLD FRONTAL PASSAGE AFTER MIDNIGHT. THE HIGHER VALLEYS
OF THE NORTHERN CLEARWATER MOUNTAINS LOOK TO BE THE MOST IMPACTED
BY ENOUGH ACCUMULATING SNOW TO WARRANT A WINTER HEADLINE.
THEREFORE THE WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW
ABOVE 3000 FEET WILL REMAIN IN PLACE. OTHER VALLEYS OF NORTH
CENTRAL IDAHO AND WESTERN MONTANA CAN ALSO EXPECT TO SEE SOME
LIGHT SNOW ACCUMULATIONS COME SATURDAY MORNING. AT THIS
TIME...LOOKS LIKE THE BEST TIME FRAME FOR CENTRAL AND SOUTHERN
VALLEYS OF WESTERN MONTANA TO SEE SNOW ACCUMULATIONS WILL BE 2 AM
THROUGH 9 AM...BUT NOT ENOUGH ACCUMULATIONS TO WARRANT HEADLINES.
HOWEVER...THIS SNOW WILL IMPACT ANY TRAVELERS HEADED OVER THE
CONTINENTAL DIVIDE PASSES. IN ADDITION...WINDS BEHIND THE FRONT
WILL BLOW THE SNOW AROUND AND REDUCE VISIBILITIES AT
TIMES...ESPECIALLY OVER THE PASSES.
A SECOND WEATHER SYSTEM AND ASSOCIATED SURFACE LOW WILL IMPACT THE
INTERMOUNTAIN REGION SUNDAY. THIS SYSTEM IS LOOKING MORE IMPRESSIVE
WITH EACH RUN...AND MAY BRING ANOTHER ROUND OF ACCUMULATING SNOW
TO THE CLEARWATER MOUNTAINS AND PORTIONS OF THE CAMAS
PRAIRIE...MAINLY GRANGEVILLE...GREER AND WHITEBIRD GRADES. WITH
CURRENT WINTER HEADLINES OUT...HAVE OPTED TO HOLD OFF ON A WATCH
BUT IF THE MODELS CONTINUE TO ADVERTISE THE STRENGTH AND POSITION
OF THIS SECOND SYSTEM THE WAY THEY ARE NOW...WINTER WEATHER
WATCHES MAY BE NECESSARY ONCE AGAIN. IN ADDITION...THE PLACEMENT
OF THIS SECOND WAVE LOOKS GOOD FOR PORTIONS OF WESTERN AND
SOUTHWEST MONTANA VALLEYS TO SEE ACCUMULATING SNOW TO THE VALLEY
FLOORS. AGAIN...AMOUNTS DO NOT APPEAR TO BE HEADLINE WORTHY...BUT
MAY IMPACT TRAVELERS. ANOTHER ROUND OF WIND IS EXPECTED WITH THIS
SECOND SYSTEM...SO MORE VISIBILITY ISSUES FROM BLOWING AND
DRIFTING SNOW ARE POSSIBLE.
A RIDGE OF HIGH PRESSURE WILL BEGIN TO BUILD OVER THE REGION
MONDAY WITH THE RIDGE AXIS SETTLING OVER THE REGION BY WEDNESDAY.
INITIALLY...THE RIDGE WILL BE WEAK ENOUGH TO ALLOW A FEW WEAK
DISTURBANCES TO MOVE THROUGH THE REGION BOTH MONDAY AND TUESDAY.
THE MAIN FOCUS OF PRECIPITATION IS EXPECTED TO BE ACROSS NORTHWEST
MONTANA BUT SHOULD REMAIN FAIRLY LIGHT WITH LITTLE IN THE WAY OF
ACCUMULATING SNOW. AS THE RIDGE AXIS MOVES OVERHEAD TUESDAY
NIGHT...SHOWER ACTIVITY WILL DWINDLE. WITH STRENGTHENING
INVERSIONS UNDER THIS STRONG UPPER LEVEL RIDGE...VALLEY FOG COULD
BECOME AN ISSUE WEDNESDAY AND THURSDAY. HAVE GONE AHEAD AND ADDED PATCHY
FOG TO THE FORECAST FOR THE TIME BEING BUT THE POTENTIAL FOR DENSE
FOG...POTENTIALLY IMPACTING HOLIDAY TRAVEL IS NOT OUT OF THE
QUESTION.
FORECAST MODELS INDICATE ANOTHER LOW PRESSURE TROUGH IMPACTING THE
NORTHERN ROCKIES FRIDAY IN TO NEXT WEEKEND. THE DETAILS AND TIMING OF
THIS SYSTEM REMAIN LOW FOR THE TIME BEING.
AVIATION...AN APPROACHING PACIFIC SYSTEM WILL CONTINUE TO
LOWER CLOUDS DECKS AND INCREASE PRECIPITATION CHANCES ACROSS THE
NORTHERN ROCKIES THIS EVENING AND OVERNIGHT. AHEAD OF THE ADVANCING
SURFACE COLD FRONT...SHOWERS WILL BE A MIX OF RAIN AND SNOW BEFORE
TURNING TO ALL SNOW AFTER 21/0600Z. PARTS OF NORTHWEST MONTANA AND
NORTH CENTRAL IDAHO WILL SEE SHOWER ACTIVITY START EARLIER FRIDAY
EVENING BEFORE CHANCES SPREAD ACROSS THE REMAINDER OF WESTERN
MONTANA BY 21/0600Z. EXPECT THE MOST INTENSE PERIODS OF
PRECIPITATION ALONG AND JUST BEHIND THE FRONTAL PASSAGE BETWEEN
21/0600Z-21/1200Z. CEILINGS ARE EXPECTED TO LOWER OVERNIGHT
CAUSING MOUNTAINS AND PASSES TO BE OBSCURED.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY FOR NORTHERN
CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS.
&&
$$
SHORT TERM...KOLATA
LONG TERM....MEAD/PALLISTER
AVIATION...KOLATA
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