[top]
000
FXUS63 KUNR 242351
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
451 PM MST TUE NOV 24 2009
.DISCUSSION...GUSTY NORTHWEST WINDS WILL DEVELOP ACROSS WESTERN SOUTH
DAKOTA THIS EVENING. THE STRONGEST WINDS CAN BE EXPECTED FROM K2WX
TO KRAP. K2WX HAS REPORTED NORTHWEST WINDS AT 30 KTS WITH GUSTS TO
38 KTS THIS PAST HOUR. HAVE INCREASED WINDS ACROSS THESE AREAS.
EXPECT WINDS TO DIMINISH AFTER MIDNIGHT. THE REST OF THE FORECAST
IS ON TRACK.
&&
.PREV DISCUSSION... /ISSUED 237 PM MST TUE NOV 24 2009/
DISCUSSION...21Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE NORTHERN
ROCKIES WITH LOW PRESSURE EXTENDING FROM SASKATCHEWAN/MANITOBA
THROUGH MINNESOTA TO A COMPACT LOW PRESSURE CENTER OVER IOWA. UPPER
ANALYSIS SHOWS A RIDGE OVER THE PACIFIC COAST WITH A TROUGH DIVING
RAPIDLY SOUTHWARD OUT OF THE CANADIAN PRAIRIE PROVINCES.
NAM DEPICTS A 120KT JET STREAK ALONG THE WEST SIDE OF THE UPPER
TROUGH HEADING SWRD ACROSS ERN MONTANA ATTM. A COLD FRONT WILL RACE
ACROSS THE CWA THIS EVENING WITH BREEZY SPOTS AHEAD OF AND BEHIND
THE FRONT. MOISTURE WILL BE LIMITED...BUT THERE WILL BE ENOUGH
FORCING FOR SOME SNOW SHOWERS ACROSS THE AREA. THE BEST CHANCE OF
ANY ACCUMULATING SNOW WILL BE LOCATED FROM THE BIGHORNS ACROSS NERN
WYOMING TO FAR SWRN SOUTH DAKOTA...INCLUDING THE BLACK HILLS. THIS
IS THE AREA WHERE THE STRONGEST UPPER DIVERGENCE ASSOCIATED WITH THE
JET STEAK...WILL BE OVERRUNNING THE AREA OF STRONGEST MID LEVEL
FRONTOGENESIS. DUE TO THE LIMITED AVAILABLE MOISTURE HAVE ADDED
RELATIVELY HIGH POPS AND LOW QPF TO THOSE AREAS TONIGHT...WITH ANY
SNOW ACCUMULATIONS EXPECTED TO BE LESS THAN AN INCH.
WEDNESDAY WILL FEATURE BREEZY AREAS WITH LOW LEVEL COLD AIR
ADVECTION IN THE MORNING...BUT THIS WILL BE REPLACED BY WARM AIR
ADVECTION LATER IN THE DAY AS UPPER RIDGE BUILDS OVER THE ROCKIES.
COOLER TEMPERATURES EXPECTED.
ON THURSDAY...AN UPPER RIDGE BUILDS OVER THE PLAINS AS ANOTHER UPPER
LEVEL TROUGH CRASHES INTO THE PACIFIC NORTHWEST. SEASONABLY PLEASANT
WEATHER IS EXPECTED FOR THANKSGIVING DAY.
EXTENDED...UPPER RIDGE WILL KEEP WARM AND DRY CONDITIONS OVER THE
AREA THROUGH FRIDAY. STRONG UPPER LEVEL TROF WILL SLIDE ACROSS THE
ROCKIES AND INTO THE PLAINS FRIDAY NIGHT INTO SATURDAY. THIS WILL
BRING A SLIGHT CHANCE FOR PRECIPITATION ALONG WITH COOLER
TEMPERATURES AND BREEZY NORTHWEST WINDS FOR THE WEEKEND. WEAK
RIDGING IS EXPECTED ON MONDAY WITH DRY CONDITIONS AND NEAR NORMAL
TEMPERATURES.
&&
.AVIATION...MVFR TO LOCAL IFR CIGS AND VISIBILITIES ARE EXPECTED
TO DEVELOP LATE TONIGHT OVER NORTHEASTERN WYOMING INTO THE BLACK
HILLS WITH LIGHT SNOW. CONDITIONS SHOULD IMPROVE AFTER 12Z
WEDNESDAY MORNING. MOST REMAINING LOCATIONS ACROSS THE SOUTH
DAKOTA PLAINS ARE EXPECTED TO REMAIN VFR.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
WETENKAMP
000
FXUS63 KUNR 242137
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
237 PM MST TUE NOV 24 2009
.DISCUSSION...21Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE NORTHERN
ROCKIES WITH LOW PRESSURE EXTENDING FROM SASKATCHEWAN/MANITOBA
THROUGH MINNESOTA TO A COMPACT LOW PRESSURE CENTER OVER IOWA. UPPER
ANALYSIS SHOWS A RIDGE OVER THE PACIFIC COAST WITH A TROUGH DIVING
RAPIDLY SOUTHWARD OUT OF THE CANADIAN PRAIRIE PROVINCES.
NAM DEPICTS A 120KT JET STREAK ALONG THE WEST SIDE OF THE UPPER
TROUGH HEADING SWRD ACROSS ERN MONTANA ATTM. A COLD FRONT WILL RACE
ACROSS THE CWA THIS EVENING WITH BREEZY SPOTS AHEAD OF AND BEHIND
THE FRONT. MOISTURE WILL BE LIMITED...BUT THERE WILL BE ENOUGH
FORCING FOR SOME SNOW SHOWERS ACROSS THE AREA. THE BEST CHANCE OF
ANY ACCUMULATING SNOW WILL BE LOCATED FROM THE BIGHORNS ACROSS NERN
WYOMING TO FAR SWRN SOUTH DAKOTA...INCLUDING THE BLACK HILLS. THIS
IS THE AREA WHERE THE STRONGEST UPPER DIVERGENCE ASSOCIATED WITH THE
JET STEAK...WILL BE OVERRUNNING THE AREA OF STRONGEST MID LEVEL
FRONTOGENESIS. DUE TO THE LIMITED AVAILABLE MOISTURE HAVE ADDED
RELATIVELY HIGH POPS AND LOW QPF TO THOSE AREAS TONIGHT...WITH ANY
SNOW ACCUMULATIONS EXPECTED TO BE LESS THAN AN INCH.
WEDNESDAY WILL FEATURE BREEZY AREAS WITH LOW LEVEL COLD AIR
ADVECTION IN THE MORNING...BUT THIS WILL BE REPLACED BY WARM AIR
ADVECTION LATER IN THE DAY AS UPPER RIDGE BUILDS OVER THE ROCKIES.
COOLER TEMPERATURES EXPECTED.
ON THURSDAY...AN UPPER RIDGE BUILDS OVER THE PLAINS AS ANOTHER UPPER
LEVEL TROUGH CRASHES INTO THE PACIFIC NORTHWEST. SEASONABLY PLEASANT
WEATHER IS EXPECTED FOR THANKSGIVING DAY.
EXTENDED...UPPER RIDGE WILL KEEP WARM AND DRY CONDITIONS OVER THE
AREA THROUGH FRIDAY. STRONG UPPER LEVEL TROF WILL SLIDE ACROSS THE
ROCKIES AND INTO THE PLAINS FRIDAY NIGHT INTO SATURDAY. THIS WILL
BRING A SLIGHT CHANCE FOR PRECIPITATION ALONG WITH COOLER
TEMPERATURES AND BREEZY NORTHWEST WINDS FOR THE WEEKEND. WEAK
RIDGING IS EXPECTED ON MONDAY WITH DRY CONDITIONS AND NEAR NORMAL
TEMPERATURES.
&&
.AVIATION...MVFR TO LOCAL IFR CIGS AND VISIBILITIES ARE EXPECTED TO
DEVELOP LATE TONIGHT OVER NORTHEASTERN WYOMING INTO THE BLACK HILLS
WITH LIGHT SNOW. CONDITIONS SHOULD IMPROVE AFTER 12Z WEDNESDAY
MORNING. MOST REMAINING LOCATIONS ACROSS THE SOUTH DAKOTA PLAINS ARE
EXPECTED TO REMAIN VFR.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
[top]
000
FXUS65 KRIW 242126
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
226 PM MST TUE NOV 24 2009
.SHORT TERM...TONIGHT THROUGH FRIDAY
COLD FRONT IS PUSHING SOUTH THROUGH NRN MT ATTM AND SHOULD PUSH
INTO NRN JOHNSON COUNTY BETWEEN 01Z AND 02Z. SHOULD SEE SOME LIGHT
SNOW AND GUSTY WINDS DEVELOP BEHIND IT AS MODERATE COMBINATION OF
SURFACE FRONT AND MID LEVEL QG FRONTOGENESIS COMBINE TO PRODUCE
MODERATE OMEGA AND A PERIOD OF LIGHT SNOW. COULD SEE A QUICK 1 TO
3 INCHES IN THE BIG HORNS AND UP TO AN INCH ACROSS THE PLAINS.
CHANCES OF SNOW DIMINISH AS YOU HEAD FURTHER SOUTH INTO NATRONA
COUNTY LATER TONIGHT BUT LOW CLOUDS ARE MORE CERTAIN. INVERSIONS
HOLDING STRONG ACROSS THE WEST WITH TEMPERATURES STRUGGLING INTO
THE MID AND UPPER 20S ACROSS THE STAR AND JACKSON VALLEYS AND
LOWER SPOTS OF YNP. RIDGE BUILDS OVER THE AREA WEDNESDAY INTO
THANKSGIVING DAY WITH STEEPENING LOW LEVEL INVERSIONS AND WARMING
MID LEVEL TEMPS. LOW CLOUDS WILL LIKELY STICK AROUND IN THE WRN
VALLEYS...ESPECIALLY LATE AT NIGHT AND IN THE MORNING. CHILLY
TEMPS WILL ALSO HOLD ON IN JACKSON AND STAR VALLEYS AND LOWER
ELEVATIONS OF YNP WITH MUCH MILDER READINGS IN THE FOOTHILLS AND
MTNS. HIGHS WILL BE 10 TO 20 DEGREES WARMER IN THE FOOTHILLS
MOUNTAINS UP TO AT LEAST 9K FEET THAN THEY WILL BE ON THE VALLEY
FLOOR. SIMILAR CONDITIONS ARE EXPECTED IN THE WIND RIVER BASIN. THE
WIND CORRIDOR WILL BE WINDY TO VERY WINDY MUCH OF THIS PERIOD
AFTER THEY KICK BACK IN AGAIN LATER WEDNESDAY AFT AND EVENING.
WINDS LOOK STRONGER WITH TIME THURSDAY INTO FRIDAY. SERPED IN
QUITE A BIT OF WIND POINTS AND HOPEFULLY THOSE WILL BE GOOD
STARTING POINTS TO WORK FROM THE NEXT FEW SHIFTS. COLD FRONT
APPROACHES LATE FRIDAY AFTERNOON OR JUST BEYOND IN THE FAR WEST
WITH POSSIBLE INVERSION EROSION IF GRADIENT IS STRONG ENOUGH.
FRIDAY COULD BE THE WARMEST DAY...ESPECIALLY FOR THE BIG HORN AND
WIND RIVER BASINS IF THE WINDS MIX DOWN. ADJUSTED SOME VALLEYS AND
BASINS DOWNWARD AND A FEW WINDY AREAS AND JOHNSON COUNTY UPWARD
THE NEXT COUPLE DAYS.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
A TROUGH WILL PUSH ACROSS THE WEST INTO THE ROCKIES FRIDAY/FRIDAY
NIGHT...REMAINING OVER THE AREA THROUGH THE HOLIDAY WEEKEND.
MEDIUM RANGE MODELS ARE SHOWING THE BULK OF THE ENERGY WITH THE
INITIAL PUSH OF THE LONGWAVE TROUGH...REMAINING WEST/NORTHWEST OF
THE AREA. MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT IN SOME DECENT
ENERGY ON THE BACKSIDE OF THIS TROUGH DIGGING FRIDAY NIGHT THROUGH
SATURDAY NIGHT INTO THE FOUR CORNERS REGION/DESERT SOUTHWEST. THE
00Z ECMWF DIGS IT FARTHER WEST/SOUTHWEST THAN THE GFS. BY SATURDAY
NIGHT...THE LONGWAVE TROUGH IS PROJECTED BY THE MEDIUM RANGE
MODELS TO BE EFFECTIVELY SPLIT...WITH A CIRCULATION OVER THE
SOUTHERN ROCKIES...AND ANOTHER ONE OVER THE NORTHERN HIGH PLAINS.
THIS LONGWAVE TROUGH IS THEN PROJECTED TO SLOWLY EJECT EAST SUNDAY
AND MONDAY...WITH THE SOUTHERN PART BECOMING CUT OFF OVER THE
SOUTHERN PLAINS. BEST CHANCES FOR SNOW WITH THIS TROUGH SHOULD BE
FRIDAY NIGHT AND SATURDAY OVER THE WEST...AS THE ENERGY ON THE
BACKSIDE OF THE TROUGH BEGINS TO DIG. DEPENDING UPON THE EXACT
TRACK WITH THE DIGGING ENERGY...IT COULD ALLOW FOR SOME UPSLOPE
CONDITIONS TO DEVELOP EAST OF THE DIVIDE SATURDAY/SATURDAY NIGHT.
CURRENTLY...IT DOES NOT APPEAR ANY SIGNIFICANT SNOWFALL IS
EXPECTED WITH THIS SYSTEM...BUT WILL OF COURSE NEED TO BE WATCHED.
ALTHOUGH PRECIPITATION REMAINS UNCERTAIN WITH THIS SYSTEM...THE
COLD FRONT PUSHING ACROSS THE AREA LATE FRIDAY AND FRIDAY NIGHT IS
NOT. DRY CONDITIONS ARE EXPECTED MONDAY...WITH A RIDGE OVER THE
AREA. HOWEVER THIS WILL BE SHORTLIVED...AS MEDIUM RANGE MODELS
SHOW A TROUGH PUSHING SOUTHEAST OUT OF BRITISH COLUMBIA MONDAY
NIGHT/TUESDAY...WITH THE GFS SLOWER THAN THE ECMWF.
THE WARMEST TEMPERATURES IN THE EXTENDED WILL BE FRIDAY...AHEAD OF
THE COLD FRONT PUSHING ACROSS THE AREA LATE FRIDAY/FRIDAY NIGHT.
TEMPERATURES SATURDAY AND SUNDAY SHOULD BE SLIGHTLY BELOW
AVERAGE...WITH A WARMING TREND MONDAY AND TUESDAY. WENT WITH THE
SLOWER SOLUTION OF THE ECMWF WITH NEXT WEEKS TROUGH...AND THUS
WITH WARMER TEMPS THAN MEX MOS.
&&
.AVIATION...
UPPER LEVEL LOW PRESSURE WILL MOVE RAPIDLY SOUTHEASTWARD TONIGHT
ACROSS EASTERN MONTANA AND THE NORTHERN PLAINS STATES. THIS LOW
PRESSURE SYSTEM WILL PUSH A COLD FRONT SOUTHWARD THROUGH EASTERN
WYOMING AND SOUTH DAKOTA THIS EVENING THROUGH THE EARLY MORNING
HOURS. WINDS ACROSS EASTERN CENTRAL WYOMING WILL SHIFT TO THE
WEST NORTHWEST AND NORTHWEST AFTER MIDNIGHT FOR A FEW HOURS BEFORE
SUNRISE. A WIND SHIFT TO THE WEST NORTHWEST CAN BE EXPECTED AT KCPR
AROUND 07Z. AN AREA OF MID LEVEL CLOUDS WILL CROSS WESTERN AND
CENTRAL WYOMING TONIGHT WITH CEILINGS FALLING TO AROUND 10 K FEET IN
MOST AREAS...EXCEPT TO BETWEEN 5 K FEET AND 8 K FEET IN THE BIGHORN
BASIN...JOHNSON COUNTY AND NATRONA COUNTY. KJAC IN THE WEST WILL
HAVE BROKEN CEILINGS AT AROUND 3500 FEET TONIGHT...AS LOWER LEVEL
MOISTURE BECOMES TRAPPED BENEATH THE RIDGE ALOFT. LIGHT SNOW
ASSOCIATED WITH THE UPPER LOW WILL CAUSE MOUNTAIN OBSCURATIONS IN
THE BIGHORNS AND BRIEF MVFR CONDITIONS IN JOHNSON COUNTY TONIGHT.
HIGH PRESSURE AT THE SURFACE AND ALOFT WILL MOVE ACROSS WESTERN
WYOMING AND INTO CENTRAL WYOMING WEDNESDAY WITH GENERALLY LIGHT
WINDS AND VFR CONDITIONS. MAINLY SCATTERED HIGH CLOUDS TO CLEAR
CONDITIONS ARE EXPECTED WEDNESDAY. WITH DEEP LOW PRESSURE MOVING
FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST
WEDNESDAY...SOUTHWEST WINDS AT KCPR COULD GUST UP TO AROUND 20 KT
IN THE AFTERNOON.
&&
.FIRE WEATHER...
A COLD FRONT WILL SLIDE SOUTH THROUGH THE EASTERN PART
OF THE DISTRICT WITH GUSTY NORTH WIND...LOW CLOUDS AND
SOME LIGHT SNOW IN JOHNSON COUNTY. OTHERWISE...A RIDGE
OF HIGH PRESSURE WILL MOVE OVER THE AREA WEDNESDAY INTO
THANKSGIVING DAY PRODUCING STEEP VALLEY AND BASIN INVERSIONS
AND DRY CONDITIONS. THE MOUNTAINS AND FOOTHILLS WILL BE
WARMER THAN MOST OF THESE TRAPPED BASINS AND VALLEYS. STRONG
SOUTHWEST WINDS WILL BLOW ACROSS THE WIND CORRIDOR FROM
EASTERN SWEETWATER COUNTY TO NATRONA COUNTY AND IN AT TIMES
IN THE HIGH COUNTRY THE NEXT SEVERAL DAYS.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...SKRBAC
LONG TERM...WM
AVIATION...SMITH
FIRE WEATHER...SKRBAC
[top]
000
FXUS65 KCYS 242039
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
139 PM MST TUE NOV 24 2009
.SHORT TERM...TONIGHT THROUGH THANKSGIVING DAY...
MID AND HIGH CLOUDS WILL SPREAD SE ACROSS MUCH OF THE CWA THIS
EVENING AS CLIPPER TYPE SYSTEM DROPS QUICKLY OUT OF SOUTHERN CANADA
ACROSS THE NORTHERN PLAINS TONIGHT. THIS SYSTEM WILL PUSH A COOL
FRONT ACROSS THE EASTERN PLAINS OF WY AND THE NEB PANHANDLE TONIGHT
BEFORE THE FRONT RETREATS BACK EAST WEDS AFTERNOON. SHALLOW LOW
LEVEL MOISTURE EXPECTED BEHIND THIS FRONT ALONG WITH SOME WEAK LIFT
WILL GENERATE LOW CLOUDINESS. SOME SNOW SHOWERS AND FLURRIES ALSO
EXPECTED FOR A SHORT TIME LATER TONIGHT FROM EAST CENTRAL WY INTO THE
NORTHEAST HALF OF THE PANHANDLE. CLEARING CONDITIONS EXPECTED WEDS
AFTERNOON AS UPPER SYSTEM MOVES AWAY AND DRIER AIR SPREADS BACK OVER
THE CWA. WARMER AND DRY WEATHER THEN SET UP FOR THANKSGIVING DAY AS
UPPER RIDGE MOVES OVER THE REGION.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY NIGHT...MAINTAINED
CONTINUITY WITH PREVIOUS FORECAST AND TRENDED THE LONG TERM FORECAST
TOWARD THE 12Z ECMWF SOLUTION. 12Z GFS AND GEM ARE NOT TOO FAR
OFF THOUGH. UPPER LEVEL RIDGE WILL BE OVERHEAD THURSDAY NIGHT AND
WILL SHIFT EAST DURING THE DAY FRIDAY AS AN UPPER TROUGH MOVES
INTO THE WESTERN US. AT THE SFC...A LEE TROUGH WILL DEEPEN IN
RESPONSE TO THE APPROACHING UPPER TROUGH THUS WILL SEE THE SFC
PRESSURE GRADIENT STRENGTHEN AND WESTERLY WINDS INCREASE IN THE
TYPICAL WINDY LOCALES. ATMOSPHERE LOOKS QUITE DRY SO WILL KEEP DRY
CONDITIONS IN THE FORECAST. EXPECT FRIDAY TO BE A FEW DEGREES
WARMER THAN THURSDAY WITH UPPER 30S AND 40S OVER THE WEST...WITH
LOW 50S TO LOW 60S IN THE EAST. BROAD SURFACE CYCLOGENESIS WILL
OCCUR ACROSS THE NORTHERN PLAINS LATE FRIDAY INTO SATURDAY AS THE
TROUGH MOVES ACROSS THE ROCKIES. A COLD FRONT ASSOCIATED WITH THE
LOW WILL MOVE THROUGH THE EASTERN ZONES BY EARLY SATURDAY MORNING.
SFC HIGH PRESSURE WILL QUICKLY BUILD OVER THE AREA BRINGING COOLER
TEMPS AND GUSTY NORTHWEST WINDS ACROSS MUCH OF THE CWA FOR
SATURDAY. MODELS DURING THIS TIME ARE BEGINNING TO SHOW SIGNS OF
AGREEMENT WITH THE TIMING AND INTENSITY OF THE TROUGH ALTHOUGH NOT
COMPLETELY. ECMWF STILL MAINTAINS A CLOSED CIRCULATION AT 500 MB
OVER THE SOUTHWEST CONNECTED TO ANOTHER CLOSED LOW OVER SOUTHERN
CANADA ALTHOUGH IS WEAKER THAN ITS PREVIOUS RUN. GFS SHOWS A DEEP
TROUGH EXTENDING ACROSS THE CENTRAL US AND IS MORE PROGRESSIVE
THAN THE ECMWF...WITH THE CANADIAN A COMBINATION OF THE TWO. SO
WITH THESE TIMING DIFFERENCES IN MIND...WILL SEE THE POTENTIAL FOR
LIGHT PRECIPITATION SATURDAY AND SATURDAY NIGHT BEHIND THE FRONT
IN UPSLOPE FLOW. WITH THE SLOWER MOVEMENT OF THE ECMWF...COULD SEE
SHOWERS LINGER THROUGH THE EARLY PART OF SUNDAY. IN
GENERAL...PRECIP TYPE WILL BE SNOW EXCEPT FOR AREAS BELOW 5000 FT
WHICH WILL BEGIN AS RAIN OR A MIX OF RAIN AND SNOW ON SATURDAY
BEFORE TURNING TO SNOW. THE UPPER TROUGH WILL MOVE OFF TO THE EAST
SUNDAY NIGHT AND HIGH PRESSURE WILL BUILD ALOFT. FAST NORTHWEST
FLOW WILL MOVE OVERHEAD MONDAY SO WILL BE A RETURN TO DRY AND
WINDY WEATHER FOR THE BEGINNING OF NEXT WEEK.
&&
.AVIATION...VFR CONDITIONS EXPECTED THROUGH THIS EVENING. SFC COLD
FRONT WILL PASS OVER EARN WY AND THE NEB PANHANDLE TONIGHT WITH
MVFR/LOCAL IFR CONDITIONS DEVELOPING OVER THAT AREA MAINLY DUE TO
LOW CIGS. SCTD SNOW SHOWERS EXPECTED MAINLY OVER THE EAST CENTRAL
WYOMING AND THE NORTHERN PANHANDLE LATER TONIGHT INTO EARLY
WEDNESDAY MORNING. CONDITIONS IMPVG WEDS LATE MORNING AND AFTERNOON
WITH VFR BY WEDS EVENING.
&&
.FIRE WEATHER...NO CONCERNS EXPECTED THROUGH THURSDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/AVIATION...RE
LONG TERM...RJM
000
FXUS63 KUNR 241605
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
905 AM MST TUE NOV 24 2009
.DISCUSSION...16Z SFC ANALYSIS SHOWS LOW PRESSURE CENTERED OVER
SWRN IA WITH HIGH PRESSURE OVER THE NORTHERN ROCKIES. SFC PRESSURE
GRADIENT WILL TIGHTEN THIS AFTERNOON AS TROUGH NOW ENTERING NERN
MT APPROACHES THE FCST AREA. HAVE RAISED WIND SPEEDS FOR THIS
AFTERNOON AND ADJUSTED CLOUD COVER DOWNWARD THIS MORNING AND
UPWARD THIS AFTERNOON.
&&
.AVIATION...MVFR CIGS ARE EXPECTED TO DEVELOP LATE TONIGHT OVER
NERN WY INTO THE BLKHLS WITH ISOLD TO SCT SHSN...WHICH MAY ALSO
BRING LCL IFR VIS IN HEAVIER PRECIP. MOST REMAINING LOCATIONS ARE
EXPECTED TO REMAIN VFR.
&&
.PREV DISCUSSION... /ISSUED 240 AM MST TUE NOV 24 2009/
DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK PATTERN OVER THE CWA
WITH NEXT LOW IN SOUTHERN AB. 110KT JET STREAK OVER BC WILL RACE
SOUTHEAST TODAY/TONIGHT...PUSHING LOW ALONG THE US/CANADIAN
BORDER. COLD FRONT WILL DEVELOP BEHIND LOW...RACING THROUGH CWA
THIS EVENING. BREEZY SPOTS AHEAD OF AND BEHIND THE FRONT. MOISTURE
WILL BE LIMITED...BUT FORCING SNAPPY GIVEN COMPACT/VIGOROUS
NATURE OF SHORTWAVE ENERGY CLOSING INTO UPPER LOW OVER SD/ND/MN
BORDER BY 12Z WEDNESDAY. WILL HAVE LOW POPS FOR -SHSN TONIGHT.
TEMPERATURES NEAR GUIDANCE.
WEDNESDAY...BREEZY SPOTS GIVEN LOW LEVEL COLD AIR ADVECTION IN THE
MORNING...BUT THIS WILL BE REPLACED BY WARM AIR ADVECTION LATER IN
THE DAY AS UPPER RIDGE BUILDS OVER THE ROCKIES. COOLER
TEMPERATURES EXPECTED.
THURSDAY...UPPER RIDGE MOVES INTO THE PLAINS AS UPPER LEVEL TROUGH
CRASHES INTO THE PACIFIC NORTHWEST. A VERY PLEASANT THANKSGIVING
DAY IS FORESEEN.
EXTENDED...UPPER RIDGE WILL KEEP WARM AND DRY CONDITIONS OVER THE
AREA THROUGH FRIDAY AFTERNOON. UPPER LEVEL TROF WILL PUSH OVER THE
ROCKIES AND INTO THE PLAINS LATE FRIDAY INTO SATURDAY. THIS WILL
BRING CHANCE FOR PRECIPITATION ALONG WITH COOLER TEMPERATURES.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
000
FXUS65 KCYS 241312
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
612 AM MST TUE NOV 24 2009
.DISCUSSION...WINDS HAVE DIMINISHED AT KARL A FEW HOURS FASTER THAN
EXPECTED. SO HAVE CANCELLED THE PREVIOUSLY ISSUED HIGH WIND
WARNING. STILL WINDS WILL GUST TO 50 MPH AT THAT SITE THROUGH THE
REST OF THE MORNING.
&&
.PREVIOUS DISCUSSION.../ISSUED AT 329 AM MST TUE NOV 24 2009/...
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
MAIN ISSUE THROUGH MID MORNING WILL BE THE STRONG WINDS OVER AND
NEAR THE LARAMIE RANGE AND IN THE ARLINGTON AREA. WINDS GUSTED
OVER 60 MPH EARLIER THIS MORNING AT KARL AND SO WENT AHEAD AND
ISSUED A HIGH WIND WARNING FOR THAT PART OF THE CWA UNTIL 16Z.
WINDS AT THE LOWEST GATE OF THE MEDICINE BOW PROFILER HAVE BEEN 40
KNOTS EARLY THIS MORNING. EXPECT WINDS TO DIMINISH LATER THIS
MORNING OVER THAT AREA AS HEIGHTS ALOFT SLOWLY RISE AND THE LOW
LEVEL HEIGHT DIFFERENCE ACROSS THE REGION DECREASES. OTHERWISE
TODAY WILL BE SEVERAL DEGREES WARMER THAN ON MONDAY DUE TO THE
RISING HEIGHTS ALOFT AND WESTERLY SURFACE WINDS. MID AND HIGH
LEVEL CLOUDS WILL INCREASE TODAY FROM THE NORTH IN ADVANCE OF THE
ALBERTA CLIPPER. THE CLIPPER IS HANDLED SIMILARLY BY MODELS AS
IT MOVES INTO THE NORTHERN PLAINS TONIGHT AND THEN CONTINUES TO
THE SOUTHEAST ON WEDNESDAY. THE GFS IS FURTHER TO THE WEST WITH
ASSOCIATED VORTICITY AND AFFECTS THE EAST HALF OF THE CWA. A
SHALLOW COLD FRONT WILL MOVE THROUGH THE EAST PART OF THE CWA
QUICKLY BETWEEN 05Z AND 12Z WEDNESDAY. AT THIS TIME WILL KEEP THE
FRONT ALONG A KPBF TO KDGW LINE BY 12Z WEDNESDAY. MODELS ALL
INCREASE MOISTURE AND MID LEVEL FRONTOGENESIS OVER THE NORTHEAST
HALF OF THE CWA TONIGHT AND THEN DECREASES WEDNESDAY MORNING.
THE RESULT IS MODEL QPF IN THE NORTHEAST HALF OF THE CWA MAINLY
BETWEEN 06Z AND 12Z. HAVE INCREASED POPS OVER THAT PART OF THE
CWA WITH SNOW AMOUNTS LESS THAN ONE HALF INCH. FLURRIES MAY IN
FACT BE A BETTER DESCRIPTION OF THE EVENT...BUT SATURATED LAYER
IN MODEL FORECAST RAOBS WAS FAIRLY DEEP FOR A SHORT TIME RESULTING
IN A PERIOD OF LIGHT ACCUMULATING SNOW. HEIGHTS ALOFT THEN
REBOUND WEDNESDAY AFTERNOON AND NIGHT AND WILL HELP TO PUSH THE
SURFACE BOUNDARY SLOWLY EAST. BY 12Z THURSDAY THE BOUNDARY LOOKS
TO BE OVER THE FAR EAST PART OF THE PANHANDLE. TEMPERATURES WILL
BE A BIT TRICKY IN THE EAST PART OF THE CWA WILL THE SHALLOW COLD
AIR MASS MOVING INTO THE AREA AND THEN ERODING EASTWARD TONIGHT
THROUGH WEDNESDAY NIGHT. AHEAD OF THE FRONT EXPECT THE GUSTY
WESTERLY WINDS TO CONTINUE. POSSIBLE MIXING BEHIND THE FRONT FOR
WEDNESDAY SHOULD ALSO PRODUCE BRISK WINDS.
LONG TERM...THURSDAY THROUGH MONDAY
PREFER THE ECMWF FOR THE LONG TERM FORECAST AS IT HAS BEEN THE MOST
CONSISTENT WITH THE HANDLING OF THE UPPER TROUGH THAT MOVES ACROSS
THE WESTERN U.S. ALSO...THE ECMWF SHOWS A SPLIT FLOW WHICH IS
COMMON DURING EL NINO WINTERS. AN UPPER RIDGE WILL BE OVER THE CWA
ON THANKSGIVING DAY WITH A THERMAL RIDGE ALSO OVER THE AREA. THIS
WILL RESULT IN VERY MILD TEMPERATURES UNDER SUNNY SKIES. THE FLOW
ALOFT WILL BECOME SW ON FRI AS THE UPPER TROUGH MOVES INLAND FROM
THE WEST COAST. THE VERY MILD AND DRY CONDITIONS WILL CONTINUE
ACROSS THE FORECAST AREA ON BLACK FRIDAY. A COLD FRONT WILL MOVE
ACROSS THE AREA FRI NIGHT...AND THIS OF COURSE LEADS TO COOLER TEMPS
ON SAT. FOR SAT...THE UPPER FLOW SPLITS WITH AN UPPER LOW FORMING
OVER AZ BY SAT NIGHT...AND ANOTHER UPPER LOW MOVING OVER THE
NORTHERN PLAINS. A WEAK DEFORMATION ZONE IS THE RESULT OVER THE
CWA. LIGHT SNOW WILL DEVELOP ACROSS THE WY PORTION OF THE CWA SAT
MORNING...WITH THE HIGHEST POPS OVER THE SOUTH CENTRAL ZONES.
BOOSTED POPS IN THESE AREAS. THE SNOW WILL SPREAD ACROSS THE
FORECAST AREA SAT NIGHT...WITH ONLY LIGHT AMOUNTS EXPECTED IN MOST
AREAS. HIGHER AMOUNTS WILL BE POSSIBLE IN THE MOUNTAINS. SUN AND
MON WILL BE RATHER COLD. FOR SUN AND SUN NIGHT...THE NRN UPPER
TROUGH AXIS WILL MOVE SOUTH...ACROSS THE EASTERN HALF OF THE
CWA...WHILE THE SOUTHERN UPPER LOW MOVES ACROSS THE SOUTHERN
ROCKIES. WILL KEEP A SLIGHT CHANCE OF SNOW IN THE FORECAST FOR MUCH
OF THE AREA. FINALLY FOR MON...AN INTERESTING THING HAPPENS. THE 2
UPPER LOWS MERGE AND FORM A SINGLE UPPER LOW OVER THE CENTRAL PLAINS
AND THE UPPER TROUGHS COME BACK INTO PHASE. HIGH TEMPERATURES WILL
BE FROM 10 TO 15 DEGREES ABOVE NORMAL ON THANKSGIVING AND
FRIDAY...AROUND NORMAL SATURDAY...AND 5 TO 10 DEGREES BELOW NORMAL
FOR SUNDAY AND MONDAY.
&&
.AVIATION...VFR CONDITIONS WILL BE OVER THE ENTIRE CWA THROUGH EARLY
TONIGHT AND THEN AGAIN WEDNESDAY AFTERNOON AND NIGHT. A COLD FRONT
WILL MOVE ACROSS THE EAST PART OF THE CWA LATER TONIGHT WITH MVFR
CEILINGS AND VISIBILITIES IN LIGHT SNOW FROM MAINLY BRIDGEPORT TO
KLSK. THOSE CONDITIONS WILL PERSIST UNTIL 15Z BEFORE IMPROVING.
OTHERWISE GUSTY SURFACE WINDS WILL BE THE MAIN CONCERN THROUGH
WEDNESDAY NIGHT. WESTERLY SURFACE WINDS WILL GUST AS HIGH AS 45
KNOTS OVER AND NEAR THE LARAMIE RANGE AND THE ARLINGTON AREA THIS
MORNING. WIND DIRECTION ALOFT IS MORE NORTHWEST...CREATING A WEAK
MOUNTAIN WAVE EVENT. BY MIDDAY...THE WINDS ALONG AND WEST OF THE
LARAMIE RANGE WILL HAVE DECREASED SOME WITH GUSTS TO 30 KNOTS.
THOSE CONDITIONS WILL GENERALLY CONTINUE NEAR THE MOUNTAINS THROUGH
12Z THURSDAY. NORTHWEST SURFACE WINDS WILL GUST AS HIGH AS 30
KNOTS OVER THE PANHANDLE ON WEDNESDAY.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH WEDNESDAY WITH COOL
TEMPERATURES AND FAIRLY HIGH RELATIVE HUMIDITIES EXPECTED. WEST
WINDS WILL GUST AS HIGH AS 60 MPH IN THE ARLINGTON AREA THROUGH MID
MORNING WITH GUSTS TO 45 MPH EXPECTED OVER AND NEAR THE MOUNTAINS
AFTER THAT TIME. THOSE GUSTY WINDS WILL CONTINUE OVER AND NEAR THE
LARAMIE AND SNOWY RANGES THROUGH WEDNESDAY NIGHT. WARMER AND DRY
WEATHER WILL BE OVER THE AREA THURSDAY AND FRIDAY WITH WINDS
INCREASING LATE THURSDAY NIGHT AND FRIDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
WEILAND/KMD
000
FXUS65 KCYS 241028
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
328 AM MST TUE NOV 24 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...
MAIN ISSUE THROUGH MID MORNING WILL BE THE STRONG WINDS OVER AND
NEAR THE LARAMIE RANGE AND IN THE ARLINGTON AREA. WINDS GUSTED
OVER 60 MPH EARLIER THIS MORNING AT KARL AND SO WENT AHEAD AND
ISSUED A HIGH WIND WARNING FOR THAT PART OF THE CWA UNTIL 16Z.
WINDS AT THE LOWEST GATE OF THE MEDICINE BOW PROFILER HAVE BEEN 40
KNOTS EARLY THIS MORNING. EXPECT WINDS TO DIMINISH LATER THIS
MORNING OVER THAT AREA AS HEIGHTS ALOFT SLOWLY RISE AND THE LOW
LEVEL HEIGHT DIFFERENCE ACROSS THE REGION DECREASES. OTHERWISE
TODAY WILL BE SEVERAL DEGREES WARMER THAN ON MONDAY DUE TO THE
RISING HEIGHTS ALOFT AND WESTERLY SURFACE WINDS. MID AND HIGH
LEVEL CLOUDS WILL INCREASE TODAY FROM THE NORTH IN ADVANCE OF THE
ALBERTA CLIPPER. THE CLIPPER IS HANDLED SIMILARLY BY MODELS AS
IT MOVES INTO THE NORTHERN PLAINS TONIGHT AND THEN CONTINUES TO
THE SOUTHEAST ON WEDNESDAY. THE GFS IS FURTHER TO THE WEST WITH
ASSOCIATED VORTICITY AND AFFECTS THE EAST HALF OF THE CWA. A
SHALLOW COLD FRONT WILL MOVE THROUGH THE EAST PART OF THE CWA
QUICKLY BETWEEN 05Z AND 12Z WEDNESDAY. AT THIS TIME WILL KEEP THE
FRONT ALONG A KPBF TO KDGW LINE BY 12Z WEDNESDAY. MODELS ALL
INCREASE MOISTURE AND MID LEVEL FRONTOGENESIS OVER THE NORTHEAST
HALF OF THE CWA TONIGHT AND THEN DECREASES WEDNESDAY MORNING.
THE RESULT IS MODEL QPF IN THE NORTHEAST HALF OF THE CWA MAINLY
BETWEEN 06Z AND 12Z. HAVE INCREASED POPS OVER THAT PART OF THE
CWA WITH SNOW AMOUNTS LESS THAN ONE HALF INCH. FLURRIES MAY IN
FACT BE A BETTER DESCRIPTION OF THE EVENT...BUT SATURATED LAYER
IN MODEL FORECAST RAOBS WAS FAIRLY DEEP FOR A SHORT TIME RESULTING
IN A PERIOD OF LIGHT ACCUMULATING SNOW. HEIGHTS ALOFT THEN
REBOUND WEDNESDAY AFTERNOON AND NIGHT AND WILL HELP TO PUSH THE
SURFACE BOUNDARY SLOWLY EAST. BY 12Z THURSDAY THE BOUNDARY LOOKS
TO BE OVER THE FAR EAST PART OF THE PANHANDLE. TEMPERATURES WILL
BE A BIT TRICKY IN THE EAST PART OF THE CWA WILL THE SHALLOW COLD
AIR MASS MOVING INTO THE AREA AND THEN ERODING EASTWARD TONIGHT
THROUGH WEDNESDAY NIGHT. AHEAD OF THE FRONT EXPECT THE GUSTY
WESTERLY WINDS TO CONTINUE. POSSIBLE MIXING BEHIND THE FRONT FOR
WEDNESDAY SHOULD ALSO PRODUCE BRISK WINDS.
.LONG TERM...THURSDAY THROUGH MONDAY
PREFER THE ECMWF FOR THE LONG TERM FORECAST AS IT HAS BEEN THE MOST
CONSISTENT WITH THE HANDLING OF THE UPPER TROUGH THAT MOVES ACROSS
THE WESTERN U.S. ALSO...THE ECMWF SHOWS A SPLIT FLOW WHICH IS
COMMON DURING EL NINO WINTERS. AN UPPER RIDGE WILL BE OVER THE CWA
ON THANKSGIVING DAY WITH A THERMAL RIDGE ALSO OVER THE AREA. THIS
WILL RESULT IN VERY MILD TEMPERATURES UNDER SUNNY SKIES. THE FLOW
ALOFT WILL BECOME SW ON FRI AS THE UPPER TROUGH MOVES INLAND FROM
THE WEST COAST. THE VERY MILD AND DRY CONDITIONS WILL CONTINUE
ACROSS THE FORECAST AREA ON BLACK FRIDAY. A COLD FRONT WILL MOVE
ACROSS THE AREA FRI NIGHT...AND THIS OF COURSE LEADS TO COOLER TEMPS
ON SAT. FOR SAT...THE UPPER FLOW SPLITS WITH AN UPPER LOW FORMING
OVER AZ BY SAT NIGHT...AND ANOTHER UPPER LOW MOVING OVER THE
NORTHERN PLAINS. A WEAK DEFORMATION ZONE IS THE RESULT OVER THE
CWA. LIGHT SNOW WILL DEVELOP ACROSS THE WY PORTION OF THE CWA SAT
MORNING...WITH THE HIGHEST POPS OVER THE SOUTH CENTRAL ZONES.
BOOSTED POPS IN THESE AREAS. THE SNOW WILL SPREAD ACROSS THE
FORECAST AREA SAT NIGHT...WITH ONLY LIGHT AMOUNTS EXPECTED IN MOST
AREAS. HIGHER AMOUNTS WILL BE POSSIBLE IN THE MOUNTAINS. SUN AND
MON WILL BE RATHER COLD. FOR SUN AND SUN NIGHT...THE NRN UPPER
TROUGH AXIS WILL MOVE SOUTH...ACROSS THE EASTERN HALF OF THE
CWA...WHILE THE SOUTHERN UPPER LOW MOVES ACROSS THE SOUTHERN
ROCKIES. WILL KEEP A SLIGHT CHANCE OF SNOW IN THE FORECAST FOR MUCH
OF THE AREA. FINALLY FOR MON...AN INTERESTING THING HAPPENS. THE 2
UPPER LOWS MERGE AND FORM A SINGLE UPPER LOW OVER THE CENTRAL PLAINS
AND THE UPPER TROUGHS COME BACK INTO PHASE. HIGH TEMPERATURES WILL
BE FROM 10 TO 15 DEGREES ABOVE NORMAL ON THANKSGIVING AND
FRIDAY...AROUND NORMAL SATURDAY...AND 5 TO 10 DEGREES BELOW NORMAL
FOR SUNDAY AND MONDAY.
&&
.AVIATION...VFR CONDITIONS WILL BE OVER THE ENTIRE CWA THROUGH EARLY
TONIGHT AND THEN AGAIN WEDNESDAY AFTERNOON AND NIGHT. A COLD FRONT
WILL MOVE ACROSS THE EAST PART OF THE CWA LATER TONIGHT WITH MVFR
CEILINGS AND VISIBILITIES IN LIGHT SNOW FROM MAINLY BRIDGEPORT TO
KLSK. THOSE CONDITIONS WILL PERSIST UNTIL 15Z BEFORE IMPROVING.
OTHERWISE GUSTY SURFACE WINDS WILL BE THE MAIN CONCERN THROUGH
WEDNESDAY NIGHT. WESTERLY SURFACE WINDS WILL GUST AS HIGH AS 45
KNOTS OVER AND NEAR THE LARAMIE RANGE AND THE ARLINGTON AREA THIS
MORNING. WIND DIRECTION ALOFT IS MORE NORTHWEST...CREATING A WEAK
MOUNTAIN WAVE EVENT. BY MIDDAY...THE WINDS ALONG AND WEST OF THE
LARAMIE RANGE WILL HAVE DECREASED SOME WITH GUSTS TO 30 KNOTS.
THOSE CONDITIONS WILL GENERALLY CONTINUE NEAR THE MOUNTAINS THROUGH
12Z THURSDAY. NORTHWEST SURFACE WINDS WILL GUST AS HIGH AS 30
KNOTS OVER THE PANHANDLE ON WEDNESDAY.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH WEDNESDAY WITH COOL
TEMPERATURES AND FAIRLY HIGH RELATIVE HUMIDITIES EXPECTED. WEST
WINDS WILL GUST AS HIGH AS 60 MPH IN THE ARLINGTON AREA THROUGH MID
MORNING WITH GUSTS TO 45 MPH EXPECTED OVER AND NEAR THE MOUNTAINS
AFTER THAT TIME. THOSE GUSTY WINDS WILL CONTINUE OVER AND NEAR THE
LARAMIE AND SNOWY RANGES THROUGH WEDNESDAY NIGHT. WARMER AND DRY
WEATHER WILL BE OVER THE AREA THURSDAY AND FRIDAY WITH WINDS
INCREASING LATE THURSDAY NIGHT AND FRIDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 9 AM FOR ZONE 110.
NE...NONE.
&&
$$
WEILAND/KMD
000
FXUS65 KRIW 241004
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
304 AM MST TUE NOV 24 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
NORTHWEST WINDS ARE STILL BLOWING ACROSS THE WIND RIVER BASIN ALONG
THE WIND RIVER CORRIDOR. THESE WINDS SHOULD RETREAT NORTHWEST TOWARD
CROWHEART AND DUBOIS AS THE NOCTURNAL INVERSION DEEPENS THIS
MORNING. WEST WINDS IN THE CODY FOOTHILLS WILL LIKELY PERSIST TODAY
AS THE BUILDING 1038MB SURFACE HIGH BUILDS INTO SOUTHWEST WY KEEPING
THE SURFACE GRADIENT IN PLACE FOR AREAS EAST OF THE DIVIDE. WILL
KEEP PATCHY FOG IN THE WESTERN VALLEYS AND BASINS FOR THIS
MORNING...NOT FORMING UNTIL AFTER 12Z SINCE THE STUBBORN TRAPPED SC
DECK IN NW WY STILL HAS TO DISSIPATE AND LOWEST TEMP/DEW POINT
DEPRESSIONS WILL NOT BE REALIZED UNTIL SUFFICIENT RADIATIONAL
COOLING TAKES PLACE AFTER THE DISSIPATION OF THE STRATEGY DECK. EVEN
IF THE LOW CLOUDS DO NOT COMPLETELY CLEAR OUT OVER THE WESTERN
VALLEYS...SOME FOG COULD STILL FORM. DJ WAS ALTERNATING BETWEEN FOG
AND LOW CLOUDS EARLIER THIS EVENING. ANY FOG THAT FORMS WILL NOT BE
WIDESPREAD SINCE THERE IS NOT A SUFFICIENT DRY LAYER ABOVE THE
INVERSION. SHOULD SEE SOME BELOW ZERO TEMP READINGS EARLY THIS
MORNING IN THE WESTERN VALLEYS AND BASINS WITH FRESH SNOW COVER IN
PLACE.
THE TROUGH CURRENTLY RIDING UP AND OVER THE RIDGE...THAT WILL BE IN
PLACE TODAY...IS NOW OVER ALBERTA AND WILL APPROACH OUR NORTHEAST
ZONES AS AN ALBERTA CLIPPER. THE CLIPPER WILL SPREAD MOST OF ITS Q
VECTOR FORCING ACROSS THE NORTHERN PLAINS WHICH THE MODELS HAVE BEEN
CONSISTENTLY ADVERTISING DURING THE LAST COUPLE OF DAYS SO WILL
TREAT THIS SYSTEM AS ONE THAT GIVES OUR NORTHEAST ZONES A GLANCING
BLOW IN THE FORM OF INCREASING NNW WIND AND SPOTTY LIGHT SNOW ACROSS
JOHNSON COUNTY AND THE BIG HORN MTNS FROM ABOUT 06Z WEDNESDAY THROUGH
18Z WED. SOME MOISTURE IS INDICATED FROM 700 TO 500MB AS WELL AS AT
THE BOUNDARY LEVEL WITH THIS FEATURE BUT DYNAMICS ARE LACKING.
CONSIDERABLE LOW CLOUDS ARE A SURE BET. THE WIND RIVER/BIG HORN
BASINS WILL EXPERIENCE A TEMPORARY WEAKENING OF THE INVERSION AS
COLDER AIR ALOFT PASSES BY OVERHEAD AND TO THE NORTHEAST. WESTERN
BASINS AND VALLEYS WILL KEEP AN INVERSION DAY AND NIGHT THROUGH AT
LEAST THURSDAY NIGHT WITH CENTRAL BASINS EXPERIENCING A REINFORCING
INVERSION BY WEDNESDAY NIGHT. ONCE THE ALBERTA CLIPPER EXITS TO THE
EAST...THE FOOTHILLS/MOUNTAINS AND THE SOUTHERN WIND CORRIDOR WILL
WARM UP NICELY FOR THANKSGIVING DAY AS SUFFICIENT MIXING FROM
SOUTHWEST WINDS COINCIDENT WITH LEE SIDE SURFACE TROUGH WILL WARM
AREAS UP LIKE CPR WITH HIGHS IN THE 50S. THE GFS INDICATES H7 TEMPS
TO WARM TO AROUND 5C BY THURSDAY EVE. BASINS AND VALLEYS ON THU WILL
REMAIN TRAPPED.
.LONG TERM...FRIDAY THROUGH TUESDAY
A TROUGH WILL PUSH ACROSS THE WEST INTO THE ROCKIES FRIDAY/FRIDAY
NIGHT...REMAINING OVER THE AREA THROUGH THE HOLIDAY WEEKEND. MEDIUM
RANGE MODELS ARE SHOWING THE BULK OF THE ENERGY WITH THE INITIAL
PUSH OF THE LONGWAVE TROUGH...REMAINING WEST/NORTHWEST OF THE
AREA. MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT IN SOME DECENT
ENERGY ON THE BACKSIDE OF THIS TROUGH DIGGING FRIDAY NIGHT THROUGH
SATURDAY NIGHT INTO THE FOUR CORNERS REGION/DESERT SOUTHWEST. THE
00Z ECMWF DIGS IT FARTHER WEST/SOUTHWEST THAN THE GFS. BY SATURDAY
NIGHT...THE LONGWAVE TROUGH IS PROJECTED BY THE MEDIUM RANGE
MODELS TO BE EFFECTIVELY SPLIT...WITH A CIRCULATION OVER THE
SOUTHERN ROCKIES...AND ANOTHER ONE OVER THE NORTHERN HIGH PLAINS.
THIS LONGWAVE TROUGH IS THEN PROJECTED TO SLOWLY EJECT EAST SUNDAY
AND MONDAY...WITH THE SOUTHERN PART BECOMING CUT OFF OVER THE
SOUTHERN PLAINS. BEST CHANCES FOR SNOW WITH THIS TROUGH SHOULD BE
FRIDAY NIGHT AND SATURDAY OVER THE WEST...AS THE ENERGY ON THE
BACKSIDE OF THE TROUGH BEGINS TO DIG. DEPENDING UPON THE EXACT
TRACK WITH THE DIGGING ENERGY...IT COULD ALLOW FOR SOME UPSLOPE
CONDITIONS TO DEVELOP EAST OF THE DIVIDE SATURDAY/SATURDAY NIGHT.
CURRENTLY...IT DOES NOT APPEAR ANY SIGNIFICANT SNOWFALL IS
EXPECTED OVER THE FORECAST AREA WITH THIS SYSTEM...BUT WILL OF
COURSE NEED TO BE WATCHED. ALTHOUGH PRECIPITATION REMAINS
UNCERTAIN WITH THIS SYSTEM...THE COLD FRONT PUSHING ACROSS THE
AREA LATE FRIDAY AND FRIDAY NIGHT IS NOT. DRY CONDITIONS ARE
EXPECTED MONDAY...WITH A RIDGE OVER THE AREA. HOWEVER THIS WILL BE
SHORTLIVED...AS MEDIUM RANGE MODELS SHOW A TROUGH PUSHING
SOUTHEAST OUT OF BRITISH COLUMBIA MONDAY NIGHT/TUESDAY...WITH THE
GFS SLOWER THAN THE ECMWF.
THE WARMEST TEMPERATURES IN THE EXTENDED WILL BE FRIDAY...AHEAD OF
THE COLD FRONT PUSHING ACROSS THE AREA LATE FRIDAY/FRIDAY NIGHT.
TEMPERATURES SATURDAY AND SUNDAY SHOULD BE SLIGHTLY BELOW
AVERAGE...WITH A WARMING TREND MONDAY AND TUESDAY. WENT WITH THE
SLOWER SOLUTION OF THE ECMWF WITH NEXT WEEKS TROUGH...AND THUS
WITH WARMER TEMPS THAN MEX MOS.
&&
.AVIATION...
VFR CONDITIONS TO PREVAIL AT ALL TERMINALS THROUGH
TUESDAY WITH THE EXCEPTION OF OCCASIONAL MVFR CEILINGS AT KJAC.
BOUNDARY LAYER MOISTURE PREVALENT ENOUGH TO GENERATE LOW CLOUDS IN
THE FAR WEST VALLEYS. SHOULD SEE KJAC CEILING IMPROVE TO VFR BETWEEN
14Z AND 17Z TUESDAY. ALSO EXPECT FREQUENT MOUNTAIN TOP OBSCURATIONS
THROUGH THE FORECAST PERIOD ACROSS NORTHWEST WYOMING IN PESKY
NORTHWEST FLOW. GUSTY WIND AT KCOD...KRKS...AND KRIW WILL DECREASE
EARLY TUESDAY MORNING. MEANWHILE...SURFACE GRADIENT WILL BECOME MORE
FAVORABLE FOR GUSTY SOUTHWEST WIND AT KCPR. INTRUSION OF SURFACE
HIGH PRESSURE BY MIDDAY TUESDAY WILL BEGIN TO RELAX THIS GRADIENT BY
00Z/WEDNESDAY. THIS SHOULD BRING DECREASING WIND TO KCPR BY SUNSET
TUESDAY. NEXT UPPER LEVEL SYSTEM WILL QUICKLY SKIRT AREAS EAST OF
THE DIVIDE TUESDAY EVENING. FOR TERMINAL SITES...EXPECT ONLY
INCREASING MID-LEVEL CLOUDS WITH NO PRECIPITATION IN ASSOCIATION
WITH THIS CLIPPER SYSTEM.
&&
.FIRE WEATHER...
STRONG VALLEY AND BASIN INVERSIONS WILL BE IN PLACE
THROUGH THURSDAY NIGHT. THE ONE MAIN INTERRUPTION TO THIS PATTERN
WILL BE AN ALBERTA CLIPPER THAT WILL AFFECT MAINLY THE BIG HORN
MOUNTAINS AND THE LOWER ELEVATIONS OF JOHNSON COUNTY TUESDAY NIGHT
AND WEDNESDAY MORNING IN THE FORM OF SPOTTY LIGHT
SNOW...CONSIDERABLE LOW CLOUDS AND INCREASED NORTH NORTHWEST WINDS
WITH THE ADJACENT WIND RIVER AND BIG HORN BASINS EXPERIENCING A
PARTIAL WEAKENING OF THE INVERSION. THE HIGHER ELEVATIONS AND
AREAS FROM THE GREEN MOUNTAINS TO CASPER WILL WARM UP INTO THE 50S
ON THANKSGIVING DAY.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...LIPSON
LONG TERM...WM
AVIATION...CNJ
FIRE WEATHER...LIPSON
000
FXUS65 KCYS 240945
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
245 AM MST TUE NOV 24 2009
.DISCUSSION...WINDS ARE GUSTING UP TO 61 MPH AT KARL. HAVE WENT
AHEAD AND ISSUED A HIGH WIND WARNING FOR THAT PART OF THE CWA UNTIL
16Z.
&&
.PREVIOUS DISCUSSION... /ISSUED AT 152 PM MST MON NOV 23 2009/...
SHORT TERM...TONIGHT THROUGH WEDNESDAY...CURRENT KCYS RADAR LOOP
SHOWS ISOLD SNOW SHOWERS/FLURRIES OVER THE MOUNTAINS OF SRN
WYOMING AND ALONG I25 NORTH OF CHEYENNE WITH DOUGLAS REPORTING A
HALF MILE VISIBILITY AND MODERATE SNOW IN THE LAST HALF HOUR.
EXPECT HIS ACTIVITY TO REMAIN ISOLATED INTO LATE THIS AFTERNOON
BEFORE DISSIPATING AROUND SUNSET AS THE COLD FRONT AND INTENSIFYING
SURFACE LOW OVER KANSAS CONTINUE TO PUSH EAST OF THE REGION TONIGHT.
EXPECT TEMPS TO REMAIN BELOW NORMAL TONIGHT WITH CLEARING SKIES
AND GOOD RADIATIONAL COOLING. WINDS WILL SLOWLY DISSIPATE BY
MIDNIGHT AS THE PRESSURE GRADIENT DECREASES ACROSS THE REGION.
THE UPPER LEVEL TROUGH CURRENTLY OVER THE AREA IS EXPECTED TO PUSH
EAST OF THE AREA INTO THE GREAT PLAINS AND GREAT LAKES REGION BY
TUESDAY RESULTING IN COOL NORTHWEST FLOW OVER SOUTHEAST WYOMING
AND THE NEBRASKA PANHANDLE...WITH HIGHS IN THE UPPER 30S TO
UPPER 40S EAST OF THE LARAMIE RANGE...AND UPPER 20S TO MID 30S
ACROSS CARBON AND ALBANY COUNTIES. MODELS IN GOOD AGREEMENT FOR
WEDNESDAY...SHOWING THE NEXT COLD FRONT MOVING INTO THE HIGH
PLAINS. THIS FRONT WILL BE DRIER...SINCE ITS EXPECTED TO MOVE INTO
THE AREA FROM THE NORTH AND HAS VERY LITTLE MOISTURE WITH IT.
HOWEVER...MODELS SHOW A STRONG 120 KT JET PUSHING ACROSS ERN
WYOMING EARLY WEDNESDAY AND SOME LLVL LIFT...SO CAN NOT RULE OUT A
BAND OF LIGHT SNOW OR FLURRIES ALONG THE FRONT OVER THE NRN
NEBRASKA PANHANDLE AND ERN WYOMING TUESDAY NIGHT INTO EARLY
WEDNESDAY MORNING. AFTER THE FRONT PUSHES ACROSS THE AREA...EXPECT
WINDS TO INCREASE FROM THE NORTH BETWEEN 25 TO 35 MPH WITH GUSTS
POSSIBLY AROUND 50 MPH WEDNESDAY ALONG AND EAST OF THE LARAMIE
RANGE WITH WIND ADVISORY CONDITIONS POSSIBLE OVER THE PANHANDLE.
OTHERWISE...COOLER THAN NORMAL TEMPS WILL CONTINUE INTO WEDNESDAY
WITH HIGHS 3 TO 7 DEGS COOLER COMPARED TO TUESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...DRY AND MILD
CONDITIONS EXPECTED FOR THANKSGIVING DAY THROUGH FRIDAY AS AN
UPPER RIDGE SHIFTS ACROSS THE REGION. SOME BREEZINESS OVER AN
CLOSE TO THE MOUNTAINS AS SOME SFC TROFFING CREATES SOME DECENT
PRESSURE GRADIENT BUT NO HIGH WINDS FORESEEN. OVER THE WEEKEND
INTO EARLY NEXT WEEK NEXT UPPER SYSTEM SHOULD AFFECT THE AREA.
MODELS DIFFER ON HANDLING OF THIS SYSTEM...MAINLY WITH HOW MUCH
ENERGY GOES WHERE...WHICH WOULD AFFECT DETAILS OVER THE CWA.
CURRENT EXTENDED FCST LOOKS TO BE IN DECENT SHAPE AND CANNOT SEE
GOOD REASON TO ALTER AT THIS TIME. WILL MAINTAIN COOLING TREND
OVER THE WEEKEND AS NEXT FRONT DUE FRIDAY NIGHT WITH SOME LIGHT
PCPN POSSIBLE MAINLY OVERT THE MTNS AND FAR NORTH SECTIONS OF THE
CWA. OTHERWISE NO BIG SURGES OF VERY COLD AIR SEEN HEADED THIS WAY
WITH GENERALLY PROGRESSIVE PATTERN KEEPING ARCTIC AIR BOTTLED WELL
NORTH.
&&
AVIATION...CURRENT OBSERVATIONS SHOW IMPROVING CONDITIONS THIS
AFTERNOON AS THE COLD FRONT...WHICH PUSHED ACROSS THE AREA
YESTERDAY EVENING AND LAST NIGHT...CONTINUES TO MOVE SOUTHEAST INTO
KANSAS AND CNTRL NEBRASKA. SNOW HAS DIMINISHED TO ISOLD SNOW
SHOWERS...MAINLY IN THE MOUNTAINS AND ALONG I25.
HOWEVER...NORTHWEST WINDS WILL REMAIN GUSTY INTO THIS EVENING WITH
SUSTAINED WINDS BETWEEN 15 TO 25 KTS AND GUSTS AROUND 35
KTS...BECOMING WEST AND DIMINISHING TO 10 TO 20 KTS LATE IN THE
EVENING. EXPECT BRIEF PERIODS OF IFR CONDITIONS IN MODERATE SNOW
SHOWERS LATE THIS AFTERNOON...WITH ACTIVITY DISSIPATING AROUND
SUNSET.
&&
FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH THURSDAY WITH COOL
TEMPERATURES AND HIGH HUMIDITIES EXPECTED.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...HIGH WIND WARNING UNTIL 9 AM FOR ZONE 110.
NE...NONE.
&&
$$
SHORT TERM/AVIATION...TJT
LONG TERM...RE
UPDATE...WEILAND
000
FXUS63 KUNR 240940
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
240 AM MST TUE NOV 24 2009
.DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK PATTERN OVER THE CWA
WITH NEXT LOW IN SOUTHERN AB. 110KT JET STREAK OVER BC WILL RACE
SOUTHEAST TODAY/TONIGHT...PUSHING LOW ALONG THE US/CANADIAN
BORDER. COLD FRONT WILL DEVELOP BEHIND LOW...RACING THROUGH CWA
THIS EVENING. BREEZY SPOTS AHEAD OF AND BEHIND THE FRONT. MOISTURE
WILL BE LIMITED...BUT FORCING SNAPPY GIVEN COMPACT/VIGOROUS
NATURE OF SHORTWAVE ENERGY CLOSING INTO UPPER LOW OVER SD/ND/MN
BORDER BY 12Z WEDNESDAY. WILL HAVE LOW POPS FOR -SHSN TONIGHT.
TEMPERATURES NEAR GUIDANCE.
WEDNESDAY...BREEZY SPOTS GIVEN LOW LEVEL COLD AIR ADVECTION IN THE
MORNING...BUT THIS WILL BE REPLACED BY WARM AIR ADVECTION LATER IN
THE DAY AS UPPER RIDGE BUILDS OVER THE ROCKIES. COOLER
TEMPERATURES EXPECTED.
THURSDAY...UPPER RIDGE MOVES INTO THE PLAINS AS UPPER LEVEL TROUGH
CRASHES INTO THE PACIFIC NORTHWEST. A VERY PLEASANT THANKSGIVING
DAY IS FORESEEN.
EXTENDED...UPPER RIDGE WILL KEEP WARM AND DRY CONDITIONS OVER THE
AREA THROUGH FRIDAY AFTERNOON. UPPER LEVEL TROF WILL PUSH OVER THE
ROCKIES AND INTO THE PLAINS LATE FRIDAY INTO SATURDAY. THIS WILL
BRING CHANCE FOR PRECIPITATION ALONG WITH COOLER TEMPERATURES.
&&
.AVIATION...MVFR CIGS ARE EXPECTED TO DEVELOP LATE TONIGHT OVER NERN
WY INTO THE BLKHLS WITH ISOLD TO SCT SHSN...WHICH MAY ALSO BRING LCL
IFR VIS IN HEAVIER PRECIP. MOST REMAINING LOCATIONS ARE EXPECTED TO
REMAIN VFR.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
HELGESON/SCHILD
000
FXUS65 KCYS 240344
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
844 PM MST MON NOV 23 2009
.UPDATE...
A DRYING AND STABILIZING AIR MASS HAS DISSIPATED ANY HINT OF
WRAP-AROUND MOISTURE ACROSS SE ZONES THIS EVENING. SATELLITE PIX
DEPICT ONLY A FEW CLOUD FRAGMENTS REMAINING ACROSS SOUTHEAST
WYOMING AND THE WESTERNMOST ROW OF COUNTIES IN NEBRASKA. SO...HAVE
REDUCED CLOUD-COVER ACROSS ALL AREAS OF THE CWA OVERNIGHT. REMOVED
PRECIP CHANCES ACROSS THE SOUTHEAST...BUT DID KEEP SMALL CHANCES
GOING ACROSS JUST THE HIGHER PEAKS OF THE SNOWY RANGE THROUGH
MIDNIGHT. OTHERWISE...CONDITIONS WILL REMAIN DRY THROUGH THE
REMAINDER OF THE OVERNIGHT. HAHN
&&
.PREV DISCUSSION... /ISSUED 152 PM MST MON NOV 23 2009/
SHORT TERM...TONIGHT THROUGH WEDNESDAY...CURRENT KCYS RADAR LOOP
SHOWS ISOLD SNOW SHOWERS/FLURRIES OVER THE MOUNTAINS OF SRN
WYOMING AND ALONG I25 NORTH OF CHEYENNE WITH DOUGLAS REPORTING A
HALF MILE VISIBILITY AND MODERATE SNOW IN THE LAST HALF HOUR.
EXPECT HIS ACTIVITY TO REMAIN ISOLATED INTO LATE THIS AFTERNOON
BEFORE DISSIPATING AROUND SUNSET AS THE COLD FRONT AND INTENSIFYING
SURFACE LOW OVER KANSAS CONTINUE TO PUSH EAST OF THE REGION TONIGHT.
EXPECT TEMPS TO REMAIN BELOW NORMAL TONIGHT WITH CLEARING SKIES
AND GOOD RADIATIONAL COOLING. WINDS WILL SLOWLY DISSIPATE BY
MIDNIGHT AS THE PRESSURE GRADIENT DECREASES ACROSS THE REGION.
THE UPPER LEVEL TROUGH CURRENTLY OVER THE AREA IS EXPECTED TO PUSH
EAST OF THE AREA INTO THE GREAT PLAINS AND GREAT LAKES REGION BY
TUESDAY RESULTING IN COOL NORTHWEST FLOW OVER SOUTHEAST WYOMING
AND THE NEBRASKA PANHANDLE...WITH HIGHS IN THE UPPER 30S TO
UPPER 40S EAST OF THE LARAMIE RANGE...AND UPPER 20S TO MID 30S
ACROSS CARBON AND ALBANY COUNTIES. MODELS IN GOOD AGREEMENT FOR
WEDNESDAY...SHOWING THE NEXT COLD FRONT MOVING INTO THE HIGH
PLAINS. THIS FRONT WILL BE DRIER...SINCE ITS EXPECTED TO MOVE INTO
THE AREA FROM THE NORTH AND HAS VERY LITTLE MOISTURE WITH IT.
HOWEVER...MODELS SHOW A STRONG 120 KT JET PUSHING ACROSS ERN
WYOMING EARLY WEDNESDAY AND SOME LLVL LIFT...SO CAN NOT RULE OUT A
BAND OF LIGHT SNOW OR FLURRIES ALONG THE FRONT OVER THE NRN
NEBRASKA PANHANDLE AND ERN WYOMING TUESDAY NIGHT INTO EARLY
WEDNESDAY MORNING. AFTER THE FRONT PUSHES ACROSS THE AREA...EXPECT
WINDS TO INCREASE FROM THE NORTH BETWEEN 25 TO 35 MPH WITH GUSTS
POSSIBLY AROUND 50 MPH WEDNESDAY ALONG AND EAST OF THE LARAMIE
RANGE WITH WIND ADVISORY CONDITIONS POSSIBLE OVER THE PANHANDLE.
OTHERWISE...COOLER THAN NORMAL TEMPS WILL CONTINUE INTO WEDNESDAY
WITH HIGHS 3 TO 7 DEGS COOLER COMPARED TO TUESDAY.
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...DRY AND MILD
CONDITIONS EXPECTED FOR THANKSGIVING DAY THROUGH FRIDAY AS AN
UPPER RIDGE SHIFTS ACROSS THE REGION. SOME BREEZINESS OVER AN
CLOSE TO THE MOUNTAINS AS SOME SFC TROFFING CREATES SOME DECENT
PRESSURE GRADIENT BUT NO HIGH WINDS FORESEEN. OVER THE WEEKEND
INTO EARLY NEXT WEEK NEXT UPPER SYSTEM SHOULD AFFECT THE AREA.
MODELS DIFFER ON HANDLING OF THIS SYSTEM...MAINLY WITH HOW MUCH
ENERGY GOES WHERE...WHICH WOULD AFFECT DETAILS OVER THE CWA.
CURRENT EXTENDED FCST LOOKS TO BE IN DECENT SHAPE AND CANNOT SEE
GOOD REASON TO ALTER AT THIS TIME. WILL MAINTAIN COOLING TREND
OVER THE WEEKEND AS NEXT FRONT DUE FRIDAY NIGHT WITH SOME LIGHT
PCPN POSSIBLE MAINLY OVERT THE MTNS AND FAR NORTH SECTIONS OF THE
CWA. OTHERWISE NO BIG SURGES OF VERY COLD AIR SEEN HEADED THIS WAY
WITH GENERALLY PROGRESSIVE PATTERN KEEPING ARCTIC AIR BOTTLED WELL
NORTH.
&&
AVIATION...CURRENT OBSERVATIONS SHOW IMPROVING CONDITIONS THIS
AFTERNOON AS THE COLD FRONT...WHICH PUSHED ACROSS THE AREA
YESTERDAY EVENING AND LAST NIGHT...CONTINUES TO MOVE SOUTHEAST INTO
KANSAS AND CNTRL NEBRASKA. SNOW HAS DIMINISHED TO ISOLD SNOW
SHOWERS...MAINLY IN THE MOUNTAINS AND ALONG I25.
HOWEVER...NORTHWEST WINDS WILL REMAIN GUSTY INTO THIS EVENING WITH
SUSTAINED WINDS BETWEEN 15 TO 25 KTS AND GUSTS AROUND 35
KTS...BECOMING WEST AND DIMINISHING TO 10 TO 20 KTS LATE IN THE
EVENING. EXPECT BRIEF PERIODS OF IFR CONDITIONS IN MODERATE SNOW
SHOWERS LATE THIS AFTERNOON...WITH ACTIVITY DISSIPATING AROUND
SUNSET.
&&
FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH THURSDAY WITH COOL
TEMPERATURES AND HIGH HUMIDITIES EXPECTED.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/AVIATION...TJT
LONG TERM...RE
000
FXUS63 KUNR 240319
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
819 PM MST MON NOV 23 2009
.DISCUSSION...LATEST SATELLITE IMAGERY SHOWS CLOUDS CLEARING FROM
WEST TO EAST ACROSS THE CWA. PRECIPITATION HAS ENDED ACROSS
SOUTH CENTRAL SOUTH DAKOTA THIS EVENING. HAVE REDUCED SKY COVER
ACROSS THE ENTIRE CWA AND REMOVED POPS ACROSS SOUTH CENTRAL SOUTH
DAKOTA.
&&
.PREV DISCUSSION... /ISSUED 241 PM MST MON NOV 23 2009/
DISCUSSION...21Z SFC ANALYSIS SHOWS LOW PRESSURE CENTERED OVER
CENTRAL KANSAS WITH A TROUGH EXTENDING INTO WESTERN MINNESOTA...AND
HIGH PRESSURE OVER THE NORTHERN ROCKIES. UPPER ANALYSIS SHOWS A
TROUGH OVER THE WESTERN DAKOTAS/NEBRASKA WITH THE UPPER HIGH OVER
EASTERN COLORADO.
REGIONAL RADAR MOSAIC SHOWS A BAND OF MOISTURE HAS ROTATED AROUND
THE SURFACE LOW AND INTO SOUTH CENTRAL SOUTH DAKOTA. THE BAND
CONTINUES TO SINK SOUTH AND EAST AND WILL BE OUT OF OUR CWA BY MID
EVENING. SKIES WILL BECOME PARTLY CLOUDY AS THE UPPER TROUGH AXIS
SHIFTS EAST TONIGHT.
TUESDAY WILL BE PARTLY CLOUDY AND WARMER AS A SHORTWAVE RIDGE
CROSSES THE NORTHERN PLAINS...BUT THE NEXT FAST MOVING UPPER LEVEL
LOW WILL ALREADY BE IMPACTING ND/MT BY EVENING. THE UPPER LOW WILL
DIVE QUICKLY INTO THE UPPER MIDWEST ON TUESDAY NIGHT. MOISTURE AND
FORCING AROUND THE UPPER TROUGH WILL BE SUFFICIENT FOR A CHANCE OF
-SHSN OVER NORTHEASTERN WYOMING...THE BLACK HILLS...AND FAR
SOUTHWESTERN SOUTH DAKOTA ON TUESDAY NIGHT. TUESDAY NIGHT WILL ALSO
BE BREEZY/WINDY AS A COLD FRONT CROSSES THE FORECAST AREA.
ON WEDNESDAY...THE UPPER LOW WILL DROP INTO IOWA AS AN UPPER RIDGE
BUILDS OVER THE NORTHERN ROCKIES. TEMPERATURES WILL BE NEAR GUIDANCE.
EXTENDED...AN UPPER LEVEL RIDGE WILL KEEP CONDITIONS WARM AND DRY
FOR THANKSGIVING DAY AND FRIDAY. HIGH TEMPERATURES ARE EXPECTED TO
BE IN THE 40S AND 50S. NEXT UPPER TROF MOVES ACROSS THE NORTHERN
PLAINS ON SATURDAY AND SUNDAY. THIS WILL BRING COOLER TEMPERATURES
AND A SLIGHT CHANCE OF PRECIPITATION TO MUCH OF THE AREA.
&&
AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST
PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
JW
000
FXUS63 KUNR 232140
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
241 PM MST MON NOV 23 2009
.DISCUSSION...21Z SFC ANALYSIS SHOWS LOW PRESSURE CENTERED OVER
CENTRAL KANSAS WITH A TROUGH EXTENDING INTO WESTERN MINNESOTA...AND
HIGH PRESSURE OVER THE NORTHERN ROCKIES. UPPER ANALYSIS SHOWS A
TROUGH OVER THE WESTERN DAKOTAS/NEBRASKA WITH THE UPPER HIGH OVER
EASTERN COLORADO.
REGIONAL RADAR MOSAIC SHOWS A BAND OF MOISTURE HAS ROTATED AROUND
THE SURFACE LOW AND INTO SOUTH CENTRAL SOUTH DAKOTA. THE BAND
CONTINUES TO SINK SOUTH AND EAST AND WILL BE OUT OF OUR CWA BY MID
EVENING. SKIES WILL BECOME PARTLY CLOUDY AS THE UPPER TROUGH AXIS
SHIFTS EAST TONIGHT.
TUESDAY WILL BE PARTLY CLOUDY AND WARMER AS A SHORTWAVE RIDGE
CROSSES THE NORTHERN PLAINS...BUT THE NEXT FAST MOVING UPPER LEVEL
LOW WILL ALREADY BE IMPACTING ND/MT BY EVENING. THE UPPER LOW WILL
DIVE QUICKLY INTO THE UPPER MIDWEST ON TUESDAY NIGHT. MOISTURE AND
FORCING AROUND THE UPPER TROUGH WILL BE SUFFICIENT FOR A CHANCE OF
-SHSN OVER NORTHEASTERN WYOMING...THE BLACK HILLS...AND FAR
SOUTHWESTERN SOUTH DAKOTA ON TUESDAY NIGHT. TUESDAY NIGHT WILL ALSO
BE BREEZY/WINDY AS A COLD FRONT CROSSES THE FORECAST AREA.
ON WEDNESDAY...THE UPPER LOW WILL DROP INTO IOWA AS AN UPPER RIDGE
BUILDS OVER THE NORTHERN ROCKIES. TEMPERATURES WILL BE NEAR GUIDANCE.
EXTENDED...AN UPPER LEVEL RIDGE WILL KEEP CONDITIONS WARM AND DRY
FOR THANKSGIVING DAY AND FRIDAY. HIGH TEMPERATURES ARE EXPECTED TO
BE IN THE 40S AND 50S. NEXT UPPER TROF MOVES ACROSS THE NORTHERN
PLAINS ON SATURDAY AND SUNDAY. THIS WILL BRING COOLER TEMPERATURES
AND A SLIGHT CHANCE OF PRECIPITATION TO MUCH OF THE AREA.
&&
.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH TUESDAY AFTERNOON.
BRISK NORTHWEST WINDS THIS AFTERNOON WILL DIMINISH OVERNIGHT.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
GR/SR
000
FXUS65 KRIW 232137
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
237 PM MST MON NOV 23 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY
BEST SNOW REPORTS CAME FROM THE TETONS AND THE STAR VALLEY FROM
OUR LAST SYSTEM WITH 10 INCHES AT THREE SITES IN THE TETONS AND 3
TO 6 INCHES IN THE STAR VALLEY. STILL SOME LINGERING LIGHT SNOW
OUT WEST WITH WEAK OROGRAPHICS AND ISENTROPIC UPGLIDE. FEW SNOW
SHOWERS DEVELOPED THIS AFTERNOON IN NATRONA COUNTY WITH SOME LOWER
WARM ADVECTION CLOUDS IN THE FAR NRN PART OF THE BIG HORN BASIN.
TRANSITORY SHORT WAVE RIDGE MOVES OVER TONIGHT IN ADVANCE OF OUR
CLIPPER SYSTEM EXPECTED TO BRUSH OUR NERN ZONES TUESDAY NIGHT.
GFS DEPICTING A LITTLE STRONGER QG FRONTOGENESIS AND SOME MODERATE
OMEGA FROM THE FAR ERN END OF THE BIG HORN BASIN TO THE BIG HORNS
AND JOHNSON COUNTY AND EVEN NRN NATRONA. KEPT GOING FORECAST WHICH
ALREADY HAD CHANCE POPS IN NATRONA COUNTY BUT DID EXTEND IT JUST A
TAD FURTHER SOUTH. SOME LOW CLOUDS MAY LINGER BEHIND THIS SYSTEM
INTO WEDNESDAY MORNING. IN THE WEST...LOW CLOUDS WILL LIKELY
LINGER OVERNIGHT WITH PATCHY FOG POSSIBLE IN THE WRN VALLEYS AND
BASINS BY MORNING...ESPECIALLY WITH ANY LOW CLOUD BREAKS.
INVERSION MAY BE DISRUPTED SLIGHTLY TUESDAY NIGHT BUT WILL RETURN
EVEN STRONGER WEDNESDAY NIGHT AS H7 TEMPS WARM ABOUT 0C. JACKSON
VALLEY AND PARTS OF YNP WILL LIKELY STRUGGLE NOT ONLY WITH HIGH
TEMPS BUT ALSO PERSISTENT LOW CLOUDS UNDER THIS PATTERN AND
POSSIBLE FOG. TRENDED TEMPS DOWN CLOSER TO MUCH COLDER GFS
GUIDANCE WITH THESE STEEPENING INVERSIONS. TEMPS COULD BE A LITTLE
TRICKIER IN THE WIND RIVER BASIN WITH NO SNOW COVER BUT WILL LEAN
TOWARDS INVERSION WINNING. THE FOOTHILLS AND MTNS WILL BE QUITE
BALMY BY THANKSGIVING DAY WITH HIGHS IN THE 40S AND 50S EVEN UP TO
9000 FEET. ONE OTHER NOTE IS POTENTIAL FOR STRONG WINDS IN THE
CODY FOOTHILLS TONIGHT AND TUESDAY MORNING. PATTERN IS SIMILAR TO
THE OCTOBER 26TH EVENT...EXCEPT MORE NWLY...WHEN THE CODY AIRPORT
BLEW 20 TO 30 MPH BUT THE WIND SIDE OF TOWN GUSTED UP NEAR 50 MPH
AND THE CLARK AREA GUSTED OVER 60 MPH. BUMPED UP WINDS CLOSER TO
THE 06Z WRF RUN WITH 30KTS PLUS OF GAP FLOW AND 20KT SUSTAINED OR
SO AROUND CODY.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
THE EXTENDED WILL BEGIN WITH A RIDGE OVER THE FORECAST AREA THURSDAY
AND THURSDAY NIGHT. THIS WILL RESULT IN DRY CONDITIONS AND ABOVE
AVERAGE TEMPERATURES THURSDAY. MEDIUM RANGE MODELS ARE IN GOOD
AGREEMENT IN A LONGWAVE TROUGH PUSHING INTO THE WEST COAST THURSDAY
NIGHT...AND THEN EAST INTO THE INTERMOUNTAIN WEST/GREAT BASIN
FRIDAY. A MAJOR COLD FRONT IS ALSO EXPECTED TO PUSH THROUGH THE
FORECAST AREA LATE FRIDAY/FRIDAY NIGHT. HOWEVER...MEDIUM RANGE
MODELS ARE HAVING MUCH DIFFICULTY IN DETERMINING WHERE THE BEST
ENERGY/SHORTWAVES WILL MOVE ACROSS THE ROCKIES...AND THUS WHERE THE
BULK OF THE PRECIP WILL OCCUR. 00Z GFS IS MUCH MORE BULLISH ON
DEVELOPING UPSLOPE CONDITIONS SATURDAY/SATURDAY NIGHT WHILE GEM AND
ECMWF KEEP THE FLOW MORE NORTHWEST...WITH MUCH LESS PRECIPITATION.
HAVING SAID THAT...HAVE INCREASED POPS SLIGHTLY FOR THIS
SYSTEM...ESPECIALLY FOR FRIDAY NIGHT WEST...AND THEN EVERYWHERE ON
SATURDAY. WILL CONTINUE WITH SLIGHT POPS MOST EVERYWHERE ON
SUNDAY...DUE TO THE UNCERTAINTY OF THIS SYSTEM. HAVE COOLED
TEMPERATURES DOWN FOR THE WEEKEND...AS ECMWF AND GFS HAVE BEEN
CONSISTENT IN BRINGING IN AT LEAST -10 DEG CELSIUS 700MB TEMPS FOR
SATURDAY AND SUNDAY...WHICH ROUGHLY TRANSLATES TO AROUND 40 DEGREES
FAHRENHEIT AT 5000 FEET IF ATMOSPHERE IS FULLY MIXED. THUS...IF
CLOUD COVER AND/OR PRECIPITATION BECOMES MORE APPARENT...THE CURRENT
FORECAST MAX TEMPS FOR THIS WEEKEND WILL NEED TO BE LOWERED.
&&
.AVIATION...
&&
.FIRE WEATHER...
A COLD NORTHERLY FLOW ALOFT WILL CONTINUE OVERNIGHT. WINDY CONDITIONS
ARE EXPECTED IN THE CODY FOOTHILLS TONIGHT WITH SOME BREEZY CONDITIONS
IN THE WIND CORRIDOR FROM NORTHEAST SWEETWATER COUNTY OVER TO CASPER.
INVERSIONS WILL BE PREVALENT IN THE WESTERN AND CENTRAL BASINS AND
VALLEYS TONIGHT. ANOTHER DISTURBANCE WILL BRUSH THE NORTHEAST PART
OF THE DISTRICT TUESDAY NIGHT WITH A CHANCE OF SNOW AND GUSTY
NORTH WIND. INVERSIONS WILL STEEPEN FURTHER WEDNESDAY INTO
THURSDAY AS A RIDGE OF HIGH PRESSURE BUILDS FOR THANKSGIVING DAY.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...SKRBAC
LONG TERM...WM
AVIATION...SMITH
FIRE WEATHER...SKRBAC
000
FXUS65 KRIW 232113
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
213 PM MST MON NOV 23 2009
.SHORT TERM...TONIGHT THROUGH THURSDAY
BEST SNOW REPORTS CAME FROM THE TETONS AND THE STAR VALLEY FROM
OUR LAST SYSTEM WITH 10 INCHES AT THREE SITES IN THE TETONS AND 3
TO 6 INCHES IN THE STAR VALLEY. STILL SOME LINGERING LIGHT SNOW
OUT WEST WITH WEAK OROGRAPHICS AND ISENTROPIC UPGLIDE. FEW SNOW
SHOWERS DEVELOPED THIS AFTERNOON IN NATRONA COUNTY WITH SOME LOWER
WARM ADVECTION CLOUDS IN THE FAR NRN PART OF THE BIG HORN BASIN.
TRANSITORY SHORT WAVE RIDGE MOVES OVER TONIGHT IN ADVANCE OF OUR
CLIPPER SYSTEM EXPECTED TO BRUSH OUR NERN ZONES TUESDAY NIGHT.
GFS DEPICTING A LITTLE STRONGER QG FRONTOGENESIS AND SOME MODERATE
OMEGA FROM THE FAR ERN END OF THE BIG HORN BASIN TO THE BIG HORNS
AND JOHNSON COUNTY AND EVEN NRN NATRONA. KEPT GOING FORECAST WHICH
ALREADY HAD CHANCE POPS IN NATRONA COUNTY BUT DID EXTEND IT JUST A
TAD FURTHER SOUTH. SOME LOW CLOUDS MAY LINGER BEHIND THIS SYSTEM
INTO WEDNESDAY MORNING. IN THE WEST...LOW CLOUDS WILL LIKELY
LINGER OVERNIGHT WITH PATCHY FOG POSSIBLE IN THE WRN VALLEYS AND
BASINS BY MORNING...ESPECIALLY WITH ANY LOW CLOUD BREAKS.
INVERSION MAY BE DISRUPTED SLIGHTLY TUESDAY NIGHT BUT WILL RETURN
EVEN STRONGER WEDNESDAY NIGHT AS H7 TEMPS WARM ABOUT 0C. JACKSON VALLEY
AND PARTS OF YNP WILL LIKELY STRUGGLE NOT ONLY WITH HIGH TEMPS BUT
ALSO PERSISTENT LOW CLOUDS UNDER THIS PATTERN AND POSSIBLE FOG.
TRENDED TEMPS DOWN CLOSER TO MUCH COLDER GFS GUIDANCE WITH THESE
STEEPENING INVERSIONS. TEMPS COULD BE A LITTLE TRICKIER IN THE
WIND RIVER BASIN WITH NO SNOW COVER BUT WILL LEAN TOWARDS
INVERSION WINNING. THE FOOTHILLS AND MTNS WILL BE QUITE BALMY BY
THANKSGIVING DAY WITH HIGHS IN THE 40S AND 50S EVEN UP TO 9000
FEET.
.LONG TERM...THURSDAY NIGHT THROUGH MONDAY
THE EXTENDED WILL BEGIN WITH A RIDGE OVER THE FORECAST AREA THURSDAY
AND THURSDAY NIGHT. THIS WILL RESULT IN DRY CONDITIONS AND ABOVE
AVERAGE TEMPERATURES THURSDAY. MEDIUM RANGE MODELS ARE IN GOOD
AGREEMENT IN A LONGWAVE TROUGH PUSHING INTO THE WEST COAST THURSDAY
NIGHT...AND THEN EAST INTO THE INTERMOUNTAIN WEST/GREAT BASIN
FRIDAY. A MAJOR COLD FRONT IS ALSO EXPECTED TO PUSH THROUGH THE
FORECAST AREA LATE FRIDAY/FRIDAY NIGHT. HOWEVER...MEDIUM RANGE
MODELS ARE HAVING MUCH DIFFICULTY IN DETERMINING WHERE THE BEST
ENERGY/SHORTWAVES WILL MOVE ACROSS THE ROCKIES...AND THUS WHERE THE
BULK OF THE PRECIP WILL OCCUR. 00Z GFS IS MUCH MORE BULLISH ON
DEVELOPING UPSLOPE CONDITIONS SATURDAY/SATURDAY NIGHT WHILE GEM AND
ECMWF KEEP THE FLOW MORE NORTHWEST...WITH MUCH LESS PRECIPITATION.
HAVING SAID THAT...HAVE INCREASED POPS SLIGHTLY FOR THIS
SYSTEM...ESPECIALLY FOR FRIDAY NIGHT WEST...AND THEN EVERYWHERE ON
SATURDAY. WILL CONTINUE WITH SLIGHT POPS MOST EVERYWHERE ON
SUNDAY...DUE TO THE UNCERTAINTY OF THIS SYSTEM. HAVE COOLED
TEMPERATURES DOWN FOR THE WEEKEND...AS ECMWF AND GFS HAVE BEEN
CONSISTENT IN BRINGING IN AT LEAST -10 DEG CELSIUS 700MB TEMPS FOR
SATURDAY AND SUNDAY...WHICH ROUGHLY TRANSLATES TO AROUND 40 DEGREES
FAHRENHEIT AT 5000 FEET IF ATMOSPHERE IS FULLY MIXED. THUS...IF
CLOUD COVER AND/OR PRECIPITATION BECOMES MORE APPARENT...THE CURRENT
FORECAST MAX TEMPS FOR THIS WEEKEND WILL NEED TO BE LOWERED.
&&
.AVIATION...
SURFACE HIGH PRESSURE IN THE NORTHERN GREAT BASIN AND THE INTERIOR
NORTHWEST U.S. WILL MOVE SLOWLY EASTWARD TONIGHT AND TUESDAY. AS THE
HIGH BUILDS IN THIS EVENING...MID LEVEL BROKEN DECKS WILL SCATTER
OUT BY 03Z AT JACKSON. ADEQUATE MID LEVEL MOISTURE AND NORTHWEST
FLOW ALOFT WILL PRODUCE ISOLATED SNOW SHOWERS IN THE HIGHER TERRAIN
OF WESTERN WYOMING WITH BRIEF MOUNTAIN OBSCURATIONS. VFR CONDITIONS
ARE EXPECTED TONIGHT ACROSS THE REMAINDER OF THE STATE. SOUTHWEST
WINDS AT KCOD WILL RANGE FROM 10 TO 15 KT THIS EVENING...AND THEN
BECOME LIGHT AFTER MIDNIGHT AS HIGH PRESSURE BUILDS INTO THE REGION
FROM THE WEST. WINDS ACROSS THE REMAINDER OF THE REGION TONIGHT WILL
DECOUPLE WITHIN A FEW HOURS OF SUNSET AND BECOME LIGHT...MAINLY LESS
THAN 8 KT. A FAST-MOVING LOW PRESSURE SYSTEM WILL DIVE FROM EASTERN
MONTANA INTO THE NORTHERN PLAINS STATES TUESDAY. A STRONG PRESSURE
GRADIENT ACROSS EASTERN WYOMING TUESDAY WILL CAUSE SOUTHWEST WIND
GUSTS OF UP TO 30 KT AT KCPR. WINDS ACROSS THE REMAINDER OF CENTRAL
AND WESTERN WYOMING WILL BE LESS THAN 10 KT UNDER THE INFLUENCE OF
HIGH PRESSURE. VFR CONDITIONS WILL PREVAIL TUESDAY WITH FEW TO
SCATTERED HIGH CLOUDS ACROSS THE REGION.
&&
.FIRE WEATHER...
A COLD NORTHERLY FLOW ALOFT WILL CONTINUE OVERNIGHT. WINDY CONDITIONS
ARE EXPECTED IN THE CODY FOOTHILLS TONIGHT WITH SOME BREEZY CONDITIONS
IN THE WIND CORRIDOR FROM NORTHEAST SWEETWATER COUNTY OVER TO CASPER.
INVERSIONS WILL BE PREVALENT IN THE WESTERN AND CENTRAL BASINS AND
VALLEYS TONIGHT. ANOTHER DISTURBANCE WILL BRUSH THE NORTHEAST PART
OF THE DISTRICT TUESDAY NIGHT WITH A CHANCE OF SNOW AND GUSTY
NORTH WIND. INVERSIONS WILL STEEPEN FURTHER WEDNESDAY INTO
THURSDAY AS A RIDGE OF HIGH PRESSURE BUILDS FOR THANKSGIVING DAY.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...SKRBAC
LONG TERM...WM
AVIATION...SMITH
FIRE WEATHER...SKRBAC
000
FXUS65 KCYS 232052
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
152 PM MST MON NOV 23 2009
.SHORT TERM...TONIGHT THROUGH WEDNESDAY...CURRENT KCYS RADAR LOOP
SHOWS ISOLD SNOW SHOWERS/FLURRIES OVER THE MOUNTAINS OF SRN
WYOMING AND ALONG I25 NORTH OF CHEYENNE WITH DOUGLAS REPORTING A
HALF MILE VISIBILITY AND MODERATE SNOW IN THE LAST HALF HOUR.
EXPECT HIS ACTIVITY TO REMAIN ISOLATED INTO LATE THIS AFTERNOON
BEFORE DISSIPATING AROUND SUNSET AS THE COLD FRONT AND INTENSIFYING
SURFACE LOW OVER KANSAS CONTINUE TO PUSH EAST OF THE REGION TONIGHT.
EXPECT TEMPS TO REMAIN BELOW NORMAL TONIGHT WITH CLEARING SKIES
AND GOOD RADIATIONAL COOLING. WINDS WILL SLOWLY DISSIPATE BY
MIDNIGHT AS THE PRESSURE GRADIENT DECREASES ACROSS THE REGION.
THE UPPER LEVEL TROUGH CURRENTLY OVER THE AREA IS EXPECTED TO PUSH
EAST OF THE AREA INTO THE GREAT PLAINS AND GREAT LAKES REGION BY
TUESDAY RESULTING IN COOL NORTHWEST FLOW OVER SOUTHEAST WYOMING
AND THE NEBRASKA PANHANDLE...WITH HIGHS IN THE UPPER 30S TO
UPPER 40S EAST OF THE LARAMIE RANGE...AND UPPER 20S TO MID 30S
ACROSS CARBON AND ALBANY COUNTIES. MODELS IN GOOD AGREEMENT FOR
WEDNESDAY...SHOWING THE NEXT COLD FRONT MOVING INTO THE HIGH
PLAINS. THIS FRONT WILL BE DRIER...SINCE ITS EXPECTED TO MOVE INTO
THE AREA FROM THE NORTH AND HAS VERY LITTLE MOISTURE WITH IT.
HOWEVER...MODELS SHOW A STRONG 120 KT JET PUSHING ACROSS ERN
WYOMING EARLY WEDNESDAY AND SOME LLVL LIFT...SO CAN NOT RULE OUT A
BAND OF LIGHT SNOW OR FLURRIES ALONG THE FRONT OVER THE NRN
NEBRASKA PANHANDLE AND ERN WYOMING TUESDAY NIGHT INTO EARLY
WEDNESDAY MORNING. AFTER THE FRONT PUSHES ACROSS THE AREA...EXPECT
WINDS TO INCREASE FROM THE NORTH BETWEEN 25 TO 35 MPH WITH GUSTS
POSSIBLY AROUND 50 MPH WEDNESDAY ALONG AND EAST OF THE LARAMIE
RANGE WITH WIND ADVISORY CONDITIONS POSSIBLE OVER THE PANHANDLE.
OTHERWISE...COOLER THAN NORMAL TEMPS WILL CONTINUE INTO WEDNESDAY
WITH HIGHS 3 TO 7 DEGS COOLER COMPARED TO TUESDAY.
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...DRY AND MILD
CONDITIONS EXPECTED FOR THANKSGIVING DAY THROUGH FRIDAY AS AN
UPPER RIDGE SHIFTS ACROSS THE REGION. SOME BREEZINESS OVER AN
CLOSE TO THE MOUNTAINS AS SOME SFC TROFFING CREATES SOME DECENT
PRESSURE GRADIENT BUT NO HIGH WINDS FORESEEN. OVER THE WEEKEND
INTO EARLY NEXT WEEK NEXT UPPER SYSTEM SHOULD AFFECT THE AREA.
MODELS DIFFER ON HANDLING OF THIS SYSTEM...MAINLY WITH HOW MUCH
ENERGY GOES WHERE...WHICH WOULD AFFECT DETAILS OVER THE CWA.
CURRENT EXTENDED FCST LOOKS TO BE IN DECENT SHAPE AND CANNOT SEE
GOOD REASON TO ALTER AT THIS TIME. WILL MAINTAIN COOLING TREND
OVER THE WEEKEND AS NEXT FRONT DUE FRIDAY NIGHT WITH SOME LIGHT
PCPN POSSIBLE MAINLY OVERT THE MTNS AND FAR NORTH SECTIONS OF THE
CWA. OTHERWISE NO BIG SURGES OF VERY COLD AIR SEEN HEADED THIS WAY
WITH GENERALLY PROGRESSIVE PATTERN KEEPING ARCTIC AIR BOTTLED WELL
NORTH.
&&
.AVIATION...CURRENT OBSERVATIONS SHOW IMPROVING CONDITIONS THIS
AFTERNOON AS THE COLD FRONT...WHICH PUSHED ACROSS THE AREA
YESTERDAY EVENING AND LAST NIGHT...CONTINUES TO MOVE SOUTHEAST INTO
KANSAS AND CNTRL NEBRASKA. SNOW HAS DIMINISHED TO ISOLD SNOW
SHOWERS...MAINLY IN THE MOUNTAINS AND ALONG I25.
HOWEVER...NORTHWEST WINDS WILL REMAIN GUSTY INTO THIS EVENING WITH
SUSTAINED WINDS BETWEEN 15 TO 25 KTS AND GUSTS AROUND 35
KTS...BECOMING WEST AND DIMINISHING TO 10 TO 20 KTS LATE IN THE
EVENING. EXPECT BRIEF PERIODS OF IFR CONDITIONS IN MODERATE SNOW
SHOWERS LATE THIS AFTERNOON...WITH ACTIVITY DISSIPATING AROUND
SUNSET.
&&
.FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH THURSDAY WITH COOL
TEMPERATURES AND HIGH HUMIDITIES EXPECTED.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/AVIATION...TJT
LONG TERM...RE
000
FXUS63 KUNR 231724
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1024 AM MST MON NOV 23 2009
.DISCUSSION...17Z SFC ANALYSIS SHOWS LOW PRESSURE OVER
NORTHEASTERN SOUTH DAKOTA WITH HIGH PRESSURE OVER SRN IDAHO AND
UTAH. TIGHT SFC PRESSURE GRADIENT OVER NORTHEASTERN WYOMING AND
WESTERN SOUTH DAKOTA WILL RESULT IN BREEZY/WINDY CONDITIONS TODAY.
UPPER ANALYSIS SHOWS THE UPPER LOW SPINNING OVER NORTHWESTERN
SOUTH DAKOTA. CLOUD COVER HAD BEEN INCREASING OVER THE FORECAST
AREA DUE TO THE UPPER TROUGH BUT NOW IT APPEARS THAT THE AXIS OF
THE UPPER TROUGH HAS SHIFTED INTO WESTERN SOUTH DAKOTA...WITH
SUBSIDENCE BREAKING UP THE STRATUS TO THE WEST OF THE TROUGH LINE.
ANTICIPATE MORE FORECAST UPDATES TODAY TO ADJUST SKY COVER AND
PRECIPITATION CHANCES AS THE UPPER LOW MOVES EAST OF THE REGION.
&&
.AVIATION...ISOLATED -SHRA OR -SHSN WILL BE FOUND TODAY AS AN UPPER
LEVEL DISTURBANCE MOVES THROUGH. MOST AREAS WILL REMAIN
VFR...THOUGH SOME AREAS OF MVFR CIGS MAY BE POSSIBLE OVER THE
BLKHLS AND PARTS OF CENTRAL SOUTH DAKOTA.
&&
.PREV DISCUSSION... /ISSUED 243 AM MST MON NOV 23 2009/
DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK LOW OVER THE BLACK
HILLS WITH COLD FRONT INTO CO AND TROUGH INTO EASTERN MT. THESE
FEATURES A REFLECTION OF UPPER LEVEL TROUGH FROM MT INTO CO. ONE
WAVE OVER MT...BUT MAIN WAVE STARTING TO TAKE OVER IN SOUTHWEST WY
IN RESPONSE TO 90KT JET DIGGING INTO BASE OF TROUGH. THIS WAVE
WILL CLOSE OFF AS UPPER LOW OVER KS TONIGHT. WITH MAIN FORCING NOW
FURTHER SOUTH...HAVE TEMPERED POPS FOR TODAY/TONIGHT...ESPECIALLY
IN THE SOUTH. WE/LL SEE LOW COVERAGE -SHSN TODAY/TONIGHT...WITH
MIXED -SHRA THIS AFTERNOON. BEST CHANCES WILL BE ALONG THE FAR
SOUTHERN BORDERS OF THE CWA. TEMPERATURES NEAR GUIDANCE.
TUESDAY...TRANSIENT SHORT WAVE RIDGE WILL BRING SOME
SUNSHINE...BUT NEXT FAST MOVING UPPER LEVEL TROUGH WILL ALREADY BE
IMPACTING ND/MT BY EVENING. MOISTURE/FORCING ON TAIL END OF WAVE
SUFFICIENT FOR A CHANCE OF -SHSN TUESDAY EVENING. BREEZY SPOTS
ALSO AS COLD FRONT BRINGS COLD AIR ADVECTION...ESPECIALLY IN THE
EAST. TEMPERATURES NEAR GUIDANCE.
WEDNESDAY...UPPER TROUGH SPINS AS UPPER LOW INTO IL. UPPER RIDGE
BUILDS OVER THE ROCKIES...BEGINNING TO AFFECT THE CWA. TEMPERATURES
NEAR GUIDANCE.
EXTENDED...AN UPPER LEVEL RIDGE WILL KEEP CONDITIONS WARM AND DRY
THROUGH FRIDAY AFTERNOON. NEXT UPPER WAVE MOVES OVER THE WEST
COAST FRIDAY AND STARTS PUSHING EAST THIS WEEKEND. THIS WILL BRING
COOLER TEMPERATURES AND POSSIBLY SOME PRECIPITATION.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
000
FXUS65 KCYS 231602
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
902 AM MST MON NOV 23 2009
.UPDATE...CURRENT RADAR LOOP SHOWS SCATTERED SNOW SHOWERS...MAINLY
ALONG AND SOUTH OF I80 THIS MORNING...STARTING TO DIMINISH TO
ISOLATED SNOW SHOWERS OR FLURRIES AS A COLD FRONT PUSHES SOUTHEAST
OF THE REGION. SNOW ACCUMULATIONS HAVE BEEN UP TO 1 INCH SO FAR THIS
MORNING WITH 4 TO 6 INCHES REPORTED IN THE MOUNTAINS. FORECAST
LOOKS ON TRACK...CONDITIONS EXPECTED TO IMPROVE BY THIS AFTERNOON
WITH COLDER THAN NORMAL TEMPERATURES THROUGH TONIGHT.
&&
.PREV DISCUSSION... /ISSUED 330 AM MST MON NOV 23 2009/
SHORT TERM...TODAY THROUGH TUESDAY NIGHT...
LIGHT SNOW WAS FALLING OVER THE SNOWY RANGE AND AT TIMES OVER
THE REST OF CARBON AND ALBANY COUNTIES. EARLIER THIS MORNING...
KRWL HAD AN INCH OF NEW SNOW AND KSAA ABOUT ONE HALF INCH. THE
RETURNS ON THE KCYS RADAR HAVE BEEN SLOWLY INCREASING SINCE 05Z.
HOWEVER...AS OF 09Z THE INTENSITY AND COVERAGE OF THE LIGHT SNOW
ON AREA RADARS WAS NOT GREAT. BAROCLINIC BAND ON SATELLITE
IMAGERY WAS BECOMING LESS ORGANZIED EARLY THIS MORNING AS WELL.
THE UPPER LOW EARLY THIS MORNING WAS STILL OVER SOUTH CENTRAL
MONTANA WITH MOST OF THE ENERGY ACROSS SOUTHERN WYOMING
ASSOCIATED WITH THE 300 MB JET. THE ASSOCIATED WAS LOCATED FROM
NEAR KLSK TO BETWEEN KLAR AND KCYS AS OF 09Z. STILL A LARGE AREA
OF 2 TO 3 MB THREE HOURLY SURFACE RISES BEHIND THE FRONT AT THAT
TIME. THE FRONT SHOULD MOVE THROUGH THE REST OF THE CWA BY 14Z.
MODELS DEVELOP THE MID AND UPPER LEVEL LOW OVER NORTHWEST KANSAS
BY 00Z WITH THE SURFACE LOW OVER EASTERN KANSAS. WITH THAT
MOVEMENT AND LIFT FROM THE 300 MB JET...MID LEVEL FRONTOGENESIS
AND SURFACE FORCING BELIEVE THAT LIGHT SNOW OR FLURRIES WILL
SPREAD OVER MUCH OF THE CWA BY MID MORNING. BASED ON CURRENT
RADAR AND SATELLITE TRENDS HAVE LOWERED THE AMOUNTS TO LESS THAN
AN ADDITIONAL INCH THROUGH THE MORNING. LARGER AMOUNTS STILL
EXPECTED IN THE SNOWY RANGE WHERE OROGRAPHICS WILL ENHANCE THE
SNOWFALL. THE REST OF TODAY WILL BE WINDY AND COOLER WITH SOME
SNOW SHOWERS. THE LAPSE RATES ARE STILL EXPECTED TO STEEPEN
WITH THE COLD TEMPERATURES ALOFT. MID LEVEL CONVERGENT AREA
THROUGH THE AFTERNOON WOULD FAVOR BANDS OF SNOW SHOWERS BETWEEN
KEAN AND KIBM AND OUTSIDE OF THE MOUNTAINS HAVE THE HIGHEST POPS
IN THAT AREA. HEIGHTS ALOFT RISE OVER THE REGION TONIGHT AND
TUESDAY AS THE STORM SYSTEM MOVES FURTHER EAST ON THE PLAINS.
SURFACE HIGH PRESSURE WILL ALSO BE OVER THE AREA...CENTERED OVER
WESTERN WYOMING. THE RESULT SHOULD BE DRY AND COOL CONDITIONS
THROUGH THAT TIME AS WELL AS A MINIMUM OF CLOUD COVER. MODELS
ARE ALL SIMILAR IN DEPICTING A SHORTWAVE TROUGH MOVING INTO THE
NORTHERN PLAINS TUESDAY NIGHT. THE FEATURE WILL PUSH A SHALLOW
COLD FRONT INTO THE EAST PART OF THE CWA AFTER 06Z WEDNESDAY. AT
THIS TIME HAVE PLACED THE FRONT FROM KPBF TO KDGW BY 12Z WEDNESDAY.
HAVE ADJUSTED THE WINDS TO MORE NORTHERLY BEHIND THE FRONT. THE
GFS AND ECMWF DEVLOP LIGHT SNOW OR FLURRIES BEHIND THE FRON THE IN
THE NORTHEAST THIRD OF THE CWA AFTER 06Z WEDNESDAY. FOR NOW HAVE
BUMPED UP POPS A BIT FOR LATER TUESDAY NIGHT IN THAT PART OF THE
CWA.
LONG TERM...WEDNESDAY THROUGH SUNDAY
PREFERRED THE ECMWF IN THE EXTENDED PERIOD...WHICH SEEMS THE MOST
CONSISTENT MODEL. THE GFS AND ECMWF ARE SIMILAR EARLY ON...BUT THEN
BEGIN TO DIFFER BY FRIDAY EVENING. THE 00Z GFS IS SLOWER AND DEEPER
WITH THE UPPER TROUGH MOVING ACROSS THE ROCKIES AND INTO THE PLAINS
THAN THE ECMWF AND ALSO ITS PREVIOUS RUN. NW CYCLONIC FLOW WILL BE
OVER THE CWA ON WED BETWEEN AN UPPER RIDGE OVER THE WRN U.S. AND AN
UPPER LOW MOVING INTO THE CENTRAL MISSISSIPPI VALLEY. SOME THICKER
CLOUDS WILL OCCUR OVER THE NE PORTION OF THE CWA DURING THE
DAY...BUT WILL DECREASE TOWARDS EVENING. AN UPPER RIDGE WILL BE
OVER THE FORECAST AREA ON THANKSGIVING DAY RESULTING IN DRY AND VERY
MILD CONDITIONS. SW FLOW WILL DEVELOP ALOFT ON BLACK FRIDAY AS THE
UPPER RIDGE AXIS MOVES EAST AND AN UPPER TROUGH MOVES OVER THE
CENTRAL AND SOUTHERN ROCKIES AND DEEPENS. VERY MILD CONDITIONS WILL
CONTINUE ACROSS THE AREA FRIDAY...BUT THEN A COLD FRONT WILL MOVE
ACROSS THE CWA LATE FRI NIGHT/EARLY SAT WHICH WILL COOL TEMPS
SIGNIFICANTLY FOR SAT AND SUN. THE UPPER TROUGH WILL ALSO MOVE
ACROSS THE CWA ON SAT. NOT VERY MUCH MOISTURE IS ASSOCIATED WITH
THIS SYSTEM...SO LEFT VERY LOW POPS IN THE FORECAST. SEEMS EL NINO
MAY BE STARTING TO INFLUENCE THE WEATHER PATTERNS OVER THE FORECAST
AREA. THE FLOW APPEARS TO SPLIT SAT NIGHT PER ECMWF WITH NORTH
UPPER FLOW OVER THE CWA THE RESULT ON SUN. AN UPPER LOW THEN
DEVELOPS IN THE SOUTHERN PORTION OF THE SPLIT...OVER THE DESERT SW.
HIGH TEMPERATURES WILL BE AROUND NORMAL FOR WED...10 TO 15 DEGREES
ABOVE NORMAL FOR THANKSGIVING AND BLACK FRIDAY...AROUND NORMAL
SAT...AND 5 TO 8 DEGREES BELOW NORMAL FOR SUN.
AVIATION...
THE STORM SYSTEM MOVING ACROSS THE CENTRAL ROCKIES TODAY WILL
PRODUCE AT LEAST PERIODS OF MVFR CEILINGS AND VISIBILITIES IN SNOW
OVER MUCH OF THE CWA. THE SNOWY RANGE WILL BE OBSCURED FOR MOST
OF THE DAY. IN ADDITION...NORTHERLY SURFACE WINDS WILL GUST AS
HIGH AS 35 KNOTS OVER THE EAST PART OF THE CWA TODAY. ICING WILL
BE A CONCERN OVER THE CWA TODAY ESPECIALLY BETWEEN 8000 FEET MSL AND
12000 FEET MSL. VFR CONDITIONS WILL RETURN TO THE CWA THIS EVENING
AS THE STORM SYSTEM MOVES ONTO THE PLAINS. WINDS WILL ALSO
GRADUALLY DECREASE EARLY TONIGHT. A SHALLOW SURFACE COLD FRONT
WILL MOVE OVER THE EAST PART OF THE CWA LATER TUESDAY NIGHT AND
MAY PRODUCE MVFR OR IFR CEILINGS BEHIND THE FRONT AS WELL AS SOME
FLURRIES.
FIRE WEATHER...
FIRE WEATHER CONCERNS WILL BE MINIMAL INTO THE MID PART OF THE
WEEK. COOL TEMPERATURES AND HIGHER RELATIVE HUMIDITIES WILL PERSIST
THROUGH THAT TIME ALONG WITH SOME LIGHT SNOW TODAY. NORTHERLY WINDS
WILL GUST AS HIGH AS 40 MPH OVER MUCH OF THE AREA TODAY. THE
WARMEST AND DRIEST DAYS THIS WEEK WILL BE THANKSGIVING DAY AND
FRIDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM/AVIATION...
LONG TERM...
000
FXUS65 KCYS 231021 AAA
AFDCYS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHEYENNE WY
330 AM MST MON NOV 23 2009
.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...
LIGHT SNOW WAS FALLING OVER THE SNOWY RANGE AND AT TIMES OVER
THE REST OF CARBON AND ALBANY COUNTIES. EARLIER THIS MORNING...
KRWL HAD AN INCH OF NEW SNOW AND KSAA ABOUT ONE HALF INCH. THE
RETURNS ON THE KCYS RADAR HAVE BEEN SLOWLY INCREASING SINCE 05Z.
HOWEVER...AS OF 09Z THE INTENSITY AND COVERAGE OF THE LIGHT SNOW
ON AREA RADARS WAS NOT GREAT. BAROCLINIC BAND ON SATELLITE
IMAGERY WAS BECOMING LESS ORGANZIED EARLY THIS MORNING AS WELL.
THE UPPER LOW EARLY THIS MORNING WAS STILL OVER SOUTH CENTRAL
MONTANA WITH MOST OF THE ENERGY ACROSS SOUTHERN WYOMING
ASSOCIATED WITH THE 300 MB JET. THE ASSOCIATED WAS LOCATED FROM
NEAR KLSK TO BETWEEN KLAR AND KCYS AS OF 09Z. STILL A LARGE AREA
OF 2 TO 3 MB THREE HOURLY SURFACE RISES BEHIND THE FRONT AT THAT
TIME. THE FRONT SHOULD MOVE THROUGH THE REST OF THE CWA BY 14Z.
MODELS DEVELOP THE MID AND UPPER LEVEL LOW OVER NORTHWEST KANSAS
BY 00Z WITH THE SURFACE LOW OVER EASTERN KANSAS. WITH THAT
MOVEMENT AND LIFT FROM THE 300 MB JET...MID LEVEL FRONTOGENESIS
AND SURFACE FORCING BELIEVE THAT LIGHT SNOW OR FLURRIES WILL
SPREAD OVER MUCH OF THE CWA BY MID MORNING. BASED ON CURRENT
RADAR AND SATELLITE TRENDS HAVE LOWERED THE AMOUNTS TO LESS THAN
AN ADDITIONAL INCH THROUGH THE MORNING. LARGER AMOUNTS STILL
EXPECTED IN THE SNOWY RANGE WHERE OROGRAPHICS WILL ENHANCE THE
SNOWFALL. THE REST OF TODAY WILL BE WINDY AND COOLER WITH SOME
SNOW SHOWERS. THE LAPSE RATES ARE STILL EXPECTED TO STEEPEN
WITH THE COLD TEMPERATURES ALOFT. MID LEVEL CONVERGENT AREA
THROUGH THE AFTERNOON WOULD FAVOR BANDS OF SNOW SHOWERS BETWEEN
KEAN AND KIBM AND OUTSIDE OF THE MOUNTAINS HAVE THE HIGHEST POPS
IN THAT AREA. HEIGHTS ALOFT RISE OVER THE REGION TONIGHT AND
TUESDAY AS THE STORM SYSTEM MOVES FURTHER EAST ON THE PLAINS.
SURFACE HIGH PRESSURE WILL ALSO BE OVER THE AREA...CENTERED OVER
WESTERN WYOMING. THE RESULT SHOULD BE DRY AND COOL CONDITIONS
THROUGH THAT TIME AS WELL AS A MINIMUM OF CLOUD COVER. MODELS
ARE ALL SIMILAR IN DEPICTING A SHORTWAVE TROUGH MOVING INTO THE
NORTHERN PLAINS TUESDAY NIGHT. THE FEATURE WILL PUSH A SHALLOW
COLD FRONT INTO THE EAST PART OF THE CWA AFTER 06Z WEDNESDAY. AT
THIS TIME HAVE PLACED THE FRONT FROM KPBF TO KDGW BY 12Z WEDNESDAY.
HAVE ADJUSTED THE WINDS TO MORE NORTHERLY BEHIND THE FRONT. THE
GFS AND ECMWF DEVLOP LIGHT SNOW OR FLURRIES BEHIND THE FRON THE IN
THE NORTHEAST THIRD OF THE CWA AFTER 06Z WEDNESDAY. FOR NOW HAVE
BUMPED UP POPS A BIT FOR LATER TUESDAY NIGHT IN THAT PART OF THE
CWA.
.LONG TERM...WEDNESDAY THROUGH SUNDAY
PREFERRED THE ECMWF IN THE EXTENDED PERIOD...WHICH SEEMS THE MOST
CONSISTENT MODEL. THE GFS AND ECMWF ARE SIMILAR EARLY ON...BUT THEN
BEGIN TO DIFFER BY FRIDAY EVENING. THE 00Z GFS IS SLOWER AND DEEPER
WITH THE UPPER TROUGH MOVING ACROSS THE ROCKIES AND INTO THE PLAINS
THAN THE ECMWF AND ALSO ITS PREVIOUS RUN. NW CYCLONIC FLOW WILL BE
OVER THE CWA ON WED BETWEEN AN UPPER RIDGE OVER THE WRN U.S. AND AN
UPPER LOW MOVING INTO THE CENTRAL MISSISSIPPI VALLEY. SOME THICKER
CLOUDS WILL OCCUR OVER THE NE PORTION OF THE CWA DURING THE
DAY...BUT WILL DECREASE TOWARDS EVENING. AN UPPER RIDGE WILL BE
OVER THE FORECAST AREA ON THANKSGIVING DAY RESULTING IN DRY AND VERY
MILD CONDITIONS. SW FLOW WILL DEVELOP ALOFT ON BLACK FRIDAY AS THE
UPPER RIDGE AXIS MOVES EAST AND AN UPPER TROUGH MOVES OVER THE
CENTRAL AND SOUTHERN ROCKIES AND DEEPENS. VERY MILD CONDITIONS WILL
CONTINUE ACROSS THE AREA FRIDAY...BUT THEN A COLD FRONT WILL MOVE
ACROSS THE CWA LATE FRI NIGHT/EARLY SAT WHICH WILL COOL TEMPS
SIGNIFICANTLY FOR SAT AND SUN. THE UPPER TROUGH WILL ALSO MOVE
ACROSS THE CWA ON SAT. NOT VERY MUCH MOISTURE IS ASSOCIATED WITH
THIS SYSTEM...SO LEFT VERY LOW POPS IN THE FORECAST. SEEMS EL NINO
MAY BE STARTING TO INFLUENCE THE WEATHER PATTERNS OVER THE FORECAST
AREA. THE FLOW APPEARS TO SPLIT SAT NIGHT PER ECMWF WITH NORTH
UPPER FLOW OVER THE CWA THE RESULT ON SUN. AN UPPER LOW THEN
DEVELOPS IN THE SOUTHERN PORTION OF THE SPLIT...OVER THE DESERT SW.
HIGH TEMPERATURES WILL BE AROUND NORMAL FOR WED...10 TO 15 DEGREES
ABOVE NORMAL FOR THANKSGIVING AND BLACK FRIDAY...AROUND NORMAL
SAT...AND 5 TO 8 DEGREES BELOW NORMAL FOR SUN.
&&
.AVIATION...
THE STORM SYSTEM MOVING ACROSS THE CENTRAL ROCKIES TODAY WILL
PRODUCE AT LEAST PERIODS OF MVFR CEILINGS AND VISIBILITIES IN SNOW
OVER MUCH OF THE CWA. THE SNOWY RANGE WILL BE OBSCURED FOR MOST
OF THE DAY. IN ADDITION...NORTHERLY SURFACE WINDS WILL GUST AS
HIGH AS 35 KNOTS OVER THE EAST PART OF THE CWA TODAY. ICING WILL
BE A CONCERN OVER THE CWA TODAY ESPECIALLY BETWEEN 8000 FEET MSL AND
12000 FEET MSL. VFR CONDITIONS WILL RETURN TO THE CWA THIS EVENING
AS THE STORM SYSTEM MOVES ONTO THE PLAINS. WINDS WILL ALSO
GRADUALLY DECREASE EARLY TONIGHT. A SHALLOW SURFACE COLD FRONT
WILL MOVE OVER THE EAST PART OF THE CWA LATER TUESDAY NIGHT AND
MAY PRODUCE MVFR OR IFR CEILINGS BEHIND THE FRONT AS WELL AS SOME
FLURRIES.
&&
.FIRE WEATHER...
FIRE WEATHER CONCERNS WILL BE MINIMAL INTO THE MID PART OF THE
WEEK. COOL TEMPERATURES AND HIGHER RELATIVE HUMIDITIES WILL PERSIST
THROUGH THAT TIME ALONG WITH SOME LIGHT SNOW TODAY. NORTHERLY WINDS
WILL GUST AS HIGH AS 40 MPH OVER MUCH OF THE AREA TODAY. THE
WARMEST AND DRIEST DAYS THIS WEEK WILL BE THANKSGIVING DAY AND
FRIDAY.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
WEILAND/KMD
000
FXUS63 KUNR 230943
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
243 AM MST MON NOV 23 2009
.DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK LOW OVER THE BLACK
HILLS WITH COLD FRONT INTO CO AND TROUGH INTO EASTERN MT. THESE
FEATURES A REFLECTION OF UPPER LEVEL TROUGH FROM MT INTO CO. ONE
WAVE OVER MT...BUT MAIN WAVE STARTING TO TAKE OVER IN SOUTHWEST WY
IN RESPONSE TO 90KT JET DIGGING INTO BASE OF TROUGH. THIS WAVE
WILL CLOSE OFF AS UPPER LOW OVER KS TONIGHT. WITH MAIN FORCING NOW
FURTHER SOUTH...HAVE TEMPERED POPS FOR TODAY/TONIGHT...ESPECIALLY
IN THE SOUTH. WE/LL SEE LOW COVERAGE -SHSN TODAY/TONIGHT...WITH
MIXED -SHRA THIS AFTERNOON. BEST CHANCES WILL BE ALONG THE FAR
SOUTHERN BORDERS OF THE CWA. TEMPERATURES NEAR GUIDANCE.
TUESDAY...TRANSIENT SHORT WAVE RIDGE WILL BRING SOME
SUNSHINE...BUT NEXT FAST MOVING UPPER LEVEL TROUGH WILL ALREADY BE
IMPACTING ND/MT BY EVENING. MOISTURE/FORCING ON TAIL END OF WAVE
SUFFICIENT FOR A CHANCE OF -SHSN TUESDAY EVENING. BREEZY SPOTS
ALSO AS COLD FRONT BRINGS COLD AIR ADVECTION...ESPECIALLY IN THE
EAST. TEMPERATURES NEAR GUIDANCE.
WEDNESDAY...UPPER TROUGH SPINS AS UPPER LOW INTO IL. UPPER RIDGE
BUILDS OVER THE ROCKIES...BEGINNING TO AFFECT THE CWA. TEMPERATURES
NEAR GUIDANCE.
EXTENDED...AN UPPER LEVEL RIDGE WILL KEEP CONDITIONS WARM AND DRY
THROUGH FRIDAY AFTERNOON. NEXT UPPER WAVE MOVES OVER THE WEST
COAST FRIDAY AND STARTS PUSHING EAST THIS WEEKEND. THIS WILL BRING
COOLER TEMPERATURES AND POSSIBLY SOME PRECIPITATION.
&&
.AVIATION...A FEW AREAS OF -SHRA OR -SHSN WILL BE POSSIBLE TODAY AS
AN UPPER LEVEL DISTURBANCE MOVES THROUGH. MOST AREAS WILL REMAIN
VFR...THOUGH SOME MVFR CIGS MAY BE POSSIBLE OVER THE BLKHLS.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
HELGESON/SCHILD
000
FXUS65 KRIW 230935
AFDRIW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
235 AM MST MON NOV 23 2009
.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
A STRONG PACIFIC COLD FRONT PLOWED ACROSS THE CWA EARLIER THIS
EVENING LEAVING IN ITS WAKE 2 TO 3 INCHES OF SNOW ACROSS MUCH OF
SWEETWATER COUNTY. THE ASSOCIATED TROUGH AXIS WILL TRACK ACROSS THE
AREA THIS MORNING ALONG WITH THE ASSOCIATED Q VECTOR FORCING. SOME
BOUNDARY LAYER MOISTURE WILL SPILL OVER EAST OF THE DIVIDE BUT MOST
OF THIS MOISTURE SHOULD REMAIN NORTH AND EAST OF THE OWL CREEK MTNS
THIS MORNING. PRESENTLY...A LARGE AREA OF VIRGA IS EVIDENT ON RADAR
EAST OF THE DIVIDE THAT SEEMS TO BE ASSOCIATED WITH THE SOUTHBOUND
CANADIAN COLD FRONT AS THE MORE SOUTHERN REFLECTIVITY ELEMENTS ARE
MOVING EAST AND THE NORTHERN MOST ELEMENTS ARE MOVING SOUTH CAUSING
FRONTAL CONVERGENCE. SOME OF THIS SNOW COULD BE REACHING THE GROUND
OVER EASTERN FREMONT COUNTY WHERE SLIGHTLY STRONGER ECHOES ARE BEING
DETECTED. THE THREAT OF SNOWFALL SHOULD PERSIST THE LONGEST IN THE
CASPER AREA WHERE Q VECTOR FORCING WILL PERSIST THE LONGEST. A
SECONDARY SHORTWAVE TROUGH ON THE BACK SIDE OF THE MAIN LONG WAVE
TROUGH WILL PUSH SOUTH ACROSS WYOMING TODAY. ISENTROPIC LIFT IN
WESTERN WY AHEAD OF THIS NEXT FEATURE SHOULD PROVIDE WESTERN WY WITH
A BRIEF PERIOD OF LIGHT SNOW THIS MORNING. WILL KEEP LOW CHANCES OF
LIGHT SNOW GOING FOR THE REMAINDER OF THE DAY TODAY MAINLY ACROSS
WESTERN WY ALONG WITH LESSER CHANCES IN THE BIG HORN MTNS TO ACCOUNT
FOR THIS SECONDARY TROUGH TO MOVE THROUGH WITH DEEP MOISTURE
LINGERING ACROSS WESTERN WY TODAY. CLOUDS WILL LINGER FOR MOST OF
THE DAY IN THE CASPER AREA TODAY ALONG WITH A POSSIBLE FLURRY AS
DEEP MOISTURE WILL LINGER THERE THROUGH LATE THIS AFTERNOON.
SIGNIFICANT DRYING WILL TAKE PLACE ELSEWHERE.
TONIGHT WILL FEATURE A COLD CLEAR NIGHT WITH SOME BELOW ZERO
READINGS IN THE WEST. SHOULD SEE SOME PATCHY FOG EARLY TUESDAY
MORNING IN THE FAR WEST VALLEYS ONCE WARM AIR BEGINS TO ADVECT INTO
THE AREA ALOFT FROM THE WEST. TUESDAY MORNING WILL FEATURE A
TRANSITORY RIDGE BEFORE THE NEXT UPSTREAM TROUGH NOW LOCATED AT 150W
OFF THE PACIFIC COAST TRAVELS UP AND OVER THE RIDGE NOW...ALONG THE
PACIFIC COAST...AND COMES DIVING SOUTHEAST OUT OF ALBERTA AS AN
ALBERTA CLIPPER AND CLIPPING OUT NORTHEAST ZONES BY TUESDAY NIGHT.
THE MODELS CONTINUE TO OSCILLATE BETWEEN MISSING OUR CWA ALTOGETHER
WITH THIS FEATURE TO AFFECTING NORTHERN WY AND MOST AREAS EAST OF
THE DIVIDE AND THIS WILL PROBABLY CONTINUE UNTIL THE TROUGH RIDES
OVER THE RIDGE. WILL GO WITH THE IDEA OF GIVING THE BIG HORN MTNS
THE HIGHEST CHANCE OF SNOWFALL WITH THIS FEATURE AND WILL UP THE
WINDS IN JOHNSON COUNTY TUESDAY NIGHT THROUGH WEDNESDAY. ANOTHER
CLEAR CALM NIGHT FOR WEDNESDAY NIGHT IS IN STORE WITH MORE AIR
ADVECTING BACK INTO THE AREA ALOFT ONCE AGAIN FOR STRENGTHENING
TEMPERATURE INVERSIONS.
.LONG TERM...THURSDAY THROUGH MONDAY
THE EXTENDED WILL BEGIN WITH A RIDGE OVER THE FORECAST AREA THURSDAY
AND THURSDAY NIGHT. THIS WILL RESULT IN DRY CONDITIONS AND ABOVE
AVERAGE TEMPERATURES THURSDAY. MEDIUM RANGE MODELS ARE IN GOOD
AGREEMENT IN A LONGWAVE TROUGH PUSHING INTO THE WEST COAST THURSDAY
NIGHT...AND THEN EAST INTO THE INTERMOUNTAIN WEST/GREAT BASIN
FRIDAY. A MAJOR COLD FRONT IS ALSO EXPECTED TO PUSH THROUGH THE
FORECAST AREA LATE FRIDAY/FRIDAY NIGHT. HOWEVER...MEDIUM RANGE
MODELS ARE HAVING MUCH DIFFICULTY IN DETERMINING WHERE THE BEST
ENERGY/SHORTWAVES WILL MOVE ACROSS THE ROCKIES...AND THUS WHERE THE
BULK OF THE PRECIP WILL OCCUR. 00Z GFS IS MUCH MORE BULLISH ON
DEVELOPING UPSLOPE CONDITIONS SATURDAY/SATURDAY NIGHT WHILE GEM AND
ECMWF KEEP THE FLOW MORE NORTHWEST...WITH MUCH LESS PRECIPITATION.
HAVING SAID THAT...HAVE INCREASED POPS SLIGHTLY FOR THIS
SYSTEM...ESPECIALLY FOR FRIDAY NIGHT WEST...AND THEN EVERYWHERE ON
SATURDAY. WILL CONTINUE WITH SLIGHT POPS MOST EVERYWHERE ON
SUNDAY...DUE TO THE UNCERTAINTY OF THIS SYSTEM. HAVE COOLED
TEMPERATURES DOWN FOR THE WEEKEND...AS ECMWF AND GFS HAVE BEEN
CONSISTENT IN BRINGING IN AT LEAST -10 DEG CELSIUS 700MB TEMPS FOR
SATURDAY AND SUNDAY...WHICH ROUGHLY TRANSLATES TO AROUND 40 DEGREES
FAHRENHEIT AT 5000 FEET IF ATMOSPHERE IS FULLY MIXED. THUS...IF
CLOUD COVER AND/OR PRECIPITATION BECOMES MORE APPARENT...THE CURRENT
FORECAST MAX TEMPS FOR THIS WEEKEND WILL NEED TO BE LOWERED.
&&
.AVIATION...
A WEATHER SYSTEM WILL CONTINUE MOVE THROUGH THE AREA TODAY. SNOW
SHOWERS WILL OCCUR OVER THE MOUNTAINS WITH MVFR CONDITIONS AT TIMES
ALONG WITH MOUNTAIN OBSCURATION. THE SNOW SHOWERS WILL BE ENDING
AROUND 00Z TUE. THE LOWER ELEVATIONS WILL SEE VFR CONDITIONS TODAY
INTO THIS EVENING. SOME MVFR CONDITIONS WILL OCCUR IN EAST CENTRAL
WY DUE TO SNOW SHOWERS...FROM KBYG TO KCPR...UNTIL 18Z...THEN VFR
CONDITIONS WILL PREVAIL THROUGH 00Z TUE.
&&
.FIRE WEATHER...
SOME SNOW WILL LINGER MAINLY IN THE CASPER AREA THIS
MORNING BEFORE THE PACIFIC WEATHER SYSTEM EXITS TO THE EAST. SOME
LIGHT SNOW WILL PERSIST IN WESTERN WYOMING TODAY AS A SECONDARY COLD
FRONT PUSHES SOUTH ACROSS THE AREA. HIGH PRESSURE WILL BUILD INTO
THE AREA TONIGHT FOR CLEAR AND COLD CONDITIONS ALONG WITH STRONG
BASIN AND VALLEY INVERSIONS. DRY WEATHER WILL BE THE RULE THROUGH MID WEEK
WITH THE EXCEPTION OF AN ALBERTA CLIPPER AFFECTING MAINLY JOHNSON
COUNTY AND THE BIG HORN MTNS WITH A CHANCE OF LIGHT SNOW AND
INCREASING NORTH WINDS TUESDAY NIGHT AND WEDNESDAY. STRONG
INVERSIONS CAN BE EXPECTED THURSDAY MORNING EAST OF THE DIVIDE
AND WEDNESDAY AND THURSDAY MORNINGS WEST OF THE DIVIDE.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...LIPSON
LONG TERM...WM
AVIATION...AR
FIRE WEATHER...LIPSON
000
FXUS65 KCYS 230431 AAA
AFDCYS
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHEYENNE WY
931 PM MST SUN NOV 22 2009
.UPDATE...TONIGHT...
FORECAST CONTINUES TO BE ON TRACK FOR THE OVERNIGHT WITH SNOW
SHOWERS EXPECTED TO INCREASE ACROSS THE WESTERN ZONES AND THE
HIGHER TERRAIN ACROSS THE SOUTHERN PORTION OF THE AREA. UP-VALLEY
FLOW NORTHWEST THROUGH THE NORTH PLATTE RIVER VALLEY THIS EVENING
HAS CAUSING INCREASED RADAR RETURNS WITH SOME SPRINKLES TURNING TO
FLURRIES LIKELY OCCURRING TO THE SOUTHEAST OF GLENDO. FIRST BAND
OF SNOW SHOWERS CREATED IFR CONDITIONS IN RAWLINS...BUT HAS SINCE
GENERALLY WEAKENED AND SHIFTED EAST. ANOTHER BAND OF SNOW SHOWERS
HAS BEEN CREATING SIGNIFICANTLY REDUCED VISIBILITIES IN SWEETWATER
COUNTY AND THIS ACTIVITY WILL MOVE INTO CARBON COUNTY BY 1000 PM
MST...SO HAVE INCREASED PRECIPITATION CHANCES TO 100 PERCENT IN
THE HIGHER TERRAIN OF THE SNOWY AND SIERRA MADRE RANGES...AND ALSO
INCREASED PRECIPITATION CHANCES ACROSS CARBON COUNTY. SNOWFALL
AMOUNTS OF 4 TO 6 INCHES IN THE SNOWY RANGE AND SIERRA MADRE ARE
STILL EXPECTED BY MIDDAY MONDAY. 1 TO 2 INCHES OF SNOW CAN BE
EXPECTED BY MIDDAY MONDAY AT LOWER ELEVATIONS OF CARBON AND ALBANY
COUNTY. AN INCH OR LESS IS EXPECTED ELSEWHERE FROM THIS QUICKLY
PASSING STORM SYSTEM.
THE BEST SUPPORT FOR WIDESPREAD SNOW SHOWERS CONTINUES TO BE AT
THE SOUTHERN EXTENT OF THE UPPER WAVE MOVING INTO THE NORTHERN
PLAINS...AND THIS IS THE AREA OF POSITIVE VORTICITY ADVECTION SET
TO MOVE ACROSS THE FORECAST AREA TONIGHT. THE FORECAST AREA WILL
ALSO BE UNDER THE INFLUENCE OF THE FAVORABLE LEFT EXIT REGION OF
A JET STREAK...HELPING TO AMPLIFY THE UPPER TROUGH...EARLY THIS
MORNING AND CHANCES FOR PRECIPITATION DIMINISH MONDAY AFTERNOON
WITH BREEZY NORTHWEST WINDS EAST OF THE LARAMIE RANGE...AND
GENERALLY WEST WINDS WEST OF THE LARAMIE RANGE...CONTINUING
THROUGH THE DAY.
&&
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
CLIPPER SYSTEM WILL SWEEP SSE THROUGH NORTHERN PLAINS TUE NIGHT
AND INTO THE CENTRAL PLAINS ON WED. THIS WILL CAUSE FLOW ALOFT
OVER THE CWA TO VEER TO NNW. BACKDOOR COLD FRONT WILL PUSH SOUTH
ACROSS MAINLY THE EASTERN HALF OF CWA TUE NIGHT AND UPSLOPE LOW
CLOUDS WILL LIKELY DEVELOP. HOWEVER...ONLY A FEW FLURRIES ARE
EXPECTED MAINLY OVER NORTHERN PARTS OF CWA TUE NIGHT/WED MORNING.
ALTHOUGH CLOUDS WILL DECREASE WED AFTERNOON...TEMPS WILL BE COOL.
STRONG UPPER RIDGE BUILDS IN FROM THE WEST FOR TURKEY DAY AND
FRIDAY FOR DRY AND WARMER CONDITIONS. A COLD FRONT WILL MOVE
ACROSS THE CWA FRIDAY NIGHT THOUGH...ENDING THE BRIEF WARM UP.
PER HPC...THE UPPER AIR DETAILS FOR THE WEEKEND ARE STILL IFFY AT
THIS POINT WITH GFS AND ECMWF SHOWING RESOLUTION DIFFERENCES.
WILL CONTINUE THE IDEA OF COOLER TEMPS BOTH SATURDAY AND SUNDAY WITH
SOME SNOW SHOWERS MAINLY OVER WESTERN AND NORTHERN PARTS OF CWA.
&&
.AVIATION...
PACIFIC COLD FRONT HAS CONTINUED TO MOVE EAST-SOUTHEAST ACROSS THE
CWA THIS EVENING WITH PERIODS OF SNOW SHOWERS NEAR RAWLINS AND IN
THE SNOWY AND SIERRA MADRE RANGES. CLOUDS WILL CONTINUE TO LOWER
BEHIND THE FRONT WITH MVFR CEILINGS AND VSBYS IN LIGHT SNOW OVER
THE SOUTHERN CWA FROM LATE THIS EVENING THROUGH SUNRISE MONDAY.
SNOW SHOWERS AND STRONG NNW WINDS WILL PREVAIL ESPECIALLY OVER THE
EASTERN HALF OF THE CWA ON MONDAY...WITH AREAS OF MVFR CEILINGS
AND VSBYS. WINDS WILL DECREASE AND SNOW SHOWERS END MONDAY NIGHT
WITH VFR CONDITIONS RETURNING.
&&
.FIRE WEATHER...
COOL TEMPERATURES AND HIGH HUMIDITIES WILL CONTINUE THROUGH THE
MIDDLE OF THE WEEK WITH SCATTERED SNOW SHOWERS INTO MONDAY
EVENING. THEREFORE...NO FIRE WEATHER CONCERNS AT THIS TIME.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...NONE.
NE...NONE.
&&
$$
SHORT TERM...SJC
AVIATION...SJC/TJT
LONG TERM...JLH
FIRE WEATHER...TJT
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