[top]
000
FXUS63 KUNR 212148
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
248 PM MST SAT NOV 21 2009
.DISCUSSION...21Z SFC ANALYSIS SHOWS LOW PRESSURE CENTERED OVER THE
SASKATCHEWAN/MANITOBA BORDER WITH A LEADING N/S ORIENTED TROUGH
ACROSS THE CENTRAL DAKOTAS...AND A TRAILING COLD FRONT CURRENTLY
CROSSING WESTERN SOUTH DAKOTA.
FOR TONIGHT...WINDS WILL DIMINISH EARLY THIS EVENING AS A WEAK SFC
HIGH SLIDES INTO THE AREA. TEMPERATURES WILL FALL TO NEAR NORMAL.
ON SUNDAY...A WEAK SHORTWAVE RIDGE WILL QUICKLY CROSS THE AREA IN
ADVANCE OF A FAST MOVING SHORTWAVE ON SUNDAY NIGHT. THE SURFACE HIGH
WILL QUICKLY SHIFT SOUTH WITH SOUTHERLY RETURN FLOW DEVELOPING OVER
WESTERN PORTIONS OF THE CWA. THERE WILL BE ENOUGH FORCING/MOISTURE
PRESENT TO INCLUDE LOW POPS ON SUNDAY NIGHT. TEMPERATURES WILL
CONTINUE NEAR GUIDANCE.
ON MONDAY...SOME DIFFERENCES REMAIN IN MODEL HANDLING OF SHORTWAVE
TROUGH. 00Z NAM/ECMWF/GEM CONTINUE TO TREND SOUTH AND EAST...WITH
THE GFS CONTINUING TO INDICATE A MORE NORTHERLY TRACK. WILL GO WITH
MODEL TRENDS AT THIS POINT...WHICH WILL KEEP BEST PRECIPITATION AWAY
FROM THE CWA...BUT WILL STILL INCLUDE A CHANCE OF SNOW OR RAIN WITH
THE BEST CHANCE OF PRECIPITATION OVER OUR SOUTH CENTRAL SOUTH DAKOTA
ZONES.
EXTENDED...UPPER LOW IS EXPECTED TO BE LOCATED OVER EASTERN NEBRASKA
INTO WESTERN IOWA ON TUESDAY...BRINGING A CHANCE OF RAN AND SNOW TO
PORTIONS OF SOUTH CENTRAL SOUTH DAKOTA. SEVERAL GFS ENSEMBLE MEMBERS
INDICATING AN UPPER LOW DEVELOPING ACROSS THIS AREA. GEM AND ECMWF
ALSO LEANING TOWARD THIS SOLUTION. SYSTEM WILL EXIT THE AREA
TUESDAY AFTERNOON. SHORTWAVE WILL SWEEP ACROSS THE CWA EARLY
WEDNESDAY MORNING. ATTM IT APPEARS CWA WILL REMAIN DRY THROUGH
MIDWEEK. EXPECT RIDGE TO BUILD ACROSS THE WESTERN CONUS LATE NEXT
WEEK. RMOP INDICATES HIGH PREDICTABILITY WITH THIS SCENARIO...SO
WILL KEEP FORECAST DRY THROUGH LATE NEXT WEEK.
&&
.AVIATION...VFR CONDITIONS CAN BE EXPECTED THROUGH THE FORECAST
PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
[top]
000
FXUS63 KABR 212042
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
242 PM CST SAT NOV 21 2009
.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT
FORECAST CHALLENGES INCLUDE TEMPERATURES THROUGHOUT THE PERIOD AND
PRECIPITATION CHANCES MAINLY LATE SUNDAY NIGHT THROUGH MONDAY NIGHT.
CURRENTLY...A COLD FRONT IS WORKING SLOWLY INTO THE FAR WESTERN
FORECAST ZONES. OUT AHEAD OF THE FRONT...BREEZY TO WINDY SOUTH
WINDS HAVE BEEN COMBINING WITH THE NOVEMBER SUNSHINE TO PUMP UP
TEMPERATURES INTO THE 50S AND 60S THROUGHOUT THE REGION.
THIS COLD FRONT MAKES ITS WAY ACROSS THE FORECAST AREA
TONIGHT...RELAXING SURFACE WINDS...WHILE TURNING THEM AROUND TO A
NORTHWEST DIRECTION. HOWEVER...THE MAIN UPPER LOW OF INTEREST IN
THE SHORT RANGE OF THE FORECAST IS APPROACHING THE REGION FROM THE
PAC NW ON SUNDAY. SO...THOSE NW WINDS WILL QUICKLY SWITCH BACK
AROUND TO THE SOUTHEAST...WHERE THEY WILL RESIDE UNTIL LATE SUNDAY
NIGHT AND MONDAY WHEN THE LOW PRESSURE SYSTEM BEGINS TO LIFT OUT
OF THE ROCKIES AND HEAD SOUTHEAST ACROSS THE WESTERN PORTIONS OF
SOUTH DAKOTA AND NEBRASKA. DURING THIS TRANSITION FROM THE ROCKIES
TO THE PLAINS STATES...THE LOW PRESSURE SYSTEM WILL BEGIN TO
DEEPEN. WHILE DOING SO...THE ATMOSPHERE TRIES TO SATURATE ENOUGH
TO GET SOME PRECIPITATION REACHING THE GROUND OUT ACROSS THE
WESTERN FORECAST ZONES. MAINTAINED THE LOW END POPS ACROSS THE
WESTERN FORECAST ZONES DURING THE FIRST HALF OF THE SUNDAY NIGHT
PERIOD...BUT THEN INCREASED THEM TO 30 TO 40 PERCENT CHANCES OF
MAINLY RAIN ACROSS THE EASTERN FORECAST ZONES LATE SUNDAY NIGHT
WHERE BETTER MOISTURE/LIFT AND FORCING WILL MAKE IT ALOT EASIER TO
PRODUCE FULL SATURATION AND GROUND-REACHING PRECIPITATION. THAT
EMPHASIS ON PRECIPITATION FALLING OVER THE EASTERN THIRD OF
FORECAST ZONES APPEARS TO BE MAINTAINED NOW BY JUST ABOUT ALL THE
MODELS. AGAIN...THE THERMAL PROFILE SEEMS TO SUPPORT A MAINLY RAIN
EVENT...PERHAPS STARTING OUT AS A LITTLE BIT OF FREEZING RAIN OR
SNOW OUT WEST SUNDAY NIGHT AS IT BEGINS TO LIFT OUT OF THE ROCKIES
AND BEFORE IT CAN EFFECTIVELY WORK TO SATURATE THE ATMOSPHERE WITH
CLOUDS/PRECIPITATION. BY MONDAY...THE FOCUS FOR PRECIPITATION
CHANCES IS DEFINITELY SWITCHING OVER TO THE EASTERN THIRD OF THE
FORECAST AREA...WITH RAIN THE PRIMARY P-TYPE. MONDAY NIGHT...AS
DEFORMATION ZONE PRECIPITATION BEGINS TO WORK SOUTH AND EAST OUT
OF THIS AREA...THE BACK EDGE OF THE PRECIPITATION BAND MAY SWITCH
OVER TO LIGHT SNOW...AND POSSIBLY PRODUCE A LIGHT COATING OF SNOW
IN SPOTS. CURRENTLY MAINTAINING UP TO AN INCH OR SO IN THE SNOW
GRIDS ACROSS THE CENTRAL PORTION OF THE FORECAST AREA /APPX THE
JAMES RIVER VALLEY REGION/. TEMPERATURES WILL SWITCH OVER TO
COOLER READINGS FOR SUNDAY AND MONDAY WITH COOLER AIR IN PLACE AND
CLOUDS/PRECIPITATION POSSIBLE.
.LONG TERM...TUESDAY THROUGH SATURDAY
THE EXTENDED PERIOD STARTS OFF WITH AN UPPER LEVEL TROUGH OVER THE
PLAINS. THE SYSTEM SHIFTS EAST DURING THE DAY...THEN A SECONDARY
LOW DROPS OUT OF CANADA AND OVER THE NORTHERN PLAINS TUESDAY
NIGHT. THE GFS HOLDS ENERGY MORE OVER THE EASTERN PLAINS AND MOVES
THE WAVE OUT ABOUT 6 TO 12 HOURS FASTER THAN THE ECMWF. STRONG
RIDGING THAT WILL BE OVER THE ROCKIES SLIDES OVER THE WESTERN
PLAINS THURSDAY NIGHT...AND OVER THE PLAINS FRIDAY. MODELS DIVERGE
QUITE A BIT AT THIS POINT AS THE GFS DROPS AN UPPER LOW ACROSS
SOUTHERN CANADA TOWARD THE GREAT LAKES...WHILE THE ECMWF INDICATES
A FAIRLY DEEP TROUGH TRACKING ACROSS THE ROCKIES TO THE PLAINS BY
THE END OF THE PERIOD.
AT THE SURFACE...A LOW PRESSURE SYSTEM WILL BE OVER MINNESOTA/IOWA
TUESDAY MORNING...WITH ONGOING PRECIPITATION ACROSS MAINLY THE
EASTERN HALF OF THE CWA. THE LOW TRACKS NORTHEAST TOWARD THE GREAT
LAKES TUESDAY AND TUESDAY NIGHT...WITH BROAD HIGH PRESSURE OVER
THE WESTERN HALF OF THE COUNTRY. MODEL TIME SECTIONS DIFFER ON
TEMPERATURES IN THE LOWER LEVELS...WITH THE NAM KEEPING
TEMPERATURES ABOVE ZERO AS HIGH AS 800 MB...AND THE GFS SHOWING
TEMPERATURES AT THE SURFACE FALLING BELOW FREEZING ON TUESDAY. FOR
THAT REASON...WILL KEEP THE PRECIPITATION ON TUESDAY AS A MENTION
OF RAIN OR SNOW. WILL KEEP A SCHC POP FOR SNOW TUESDAY NIGHT
ACROSS THE EASTERN CWA AS THE SECONDARY UPPER WAVE MOVES OVERHEAD.
THE SURFACE HIGH TO THE WEST BEGINS TO BROADEN EASTWARD
WEDNESDAY...WITH THE HIGH REMAINING DOMINANT THROUGH THE DAY
FRIDAY. AT THAT TIME...A TROUGH BEGINS TO DIG DOWN THE LEE OF THE
ROCKIES...AND TRACKS ACROSS THE PLAINS AS A COLD FRONT FRIDAY
NIGHT. LITTLE IN THE WAY OF MOISTURE AROUND...SO WILL NOT MENTION
PRECIPITATION WITH THE FRONTAL PASSAGE. HIGH PRESSURE STARTS TO
NOSE BACK OVER THE REGION BEHIND THE EXITING FRONT ON SATURDAY.
H85 TEMPS REMAIN BELOW ZERO THROUGH MUCH OF THE PERIOD...WITH THE
EXCEPTION OF FRIDAY WHEN WAA DEVELOPS AHEAD OF THE APPROACHING
COLD FRONT. GENERALLY LOOKING AT NEAR TO SLIGHTLY ABOVE NORMAL
TEMPERATURES THROUGH THE PERIOD...WITH FRIDAY BEING THE WARMEST
DAY.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL TONIGHT WITH SCT-BKN HIGH CLOUDS AOA 15K
FEET. MAY SEE SOME HIGH LEVEL IFR TO MVFR CLOUDS STREAM OVER THE
FAR EASTERN CWA LATE TONIGHT AND EARLY SUNDAY MORNING...MAINLY
AFFECTING KATY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
SHORT TERM...DORN
LONG TERM...PARKIN
AVIATION...PARKIN
WEATHER.GOV/ABERDEEN
000
FXUS63 KUNR 211746
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1046 AM MST SAT NOV 21 2009
.DISCUSSION...17Z SFC ANALYSIS SHOWS LOW PRESSURE OVER CENTRAL
SASKATCHEWAN WITH A LEADING TROUGH EXTENDING ACROSS WESTERN NORTH
DAKOTA AND CENTRAL SOUTH DAKOTA...WITH A COOL FRONT EXTENDING FROM
WESTERN NORTH DAKOTA TO NEAR KGCC IN NORTHEASTERN WYOMING. A BAND
OF CIRRUS WAS LOCATED OVER WESTERN SOUTH DAKOTA MOVING SLOWLY
EAST. THE TIGHT PRESSURE GRADIENT ASSOCIATED WITH THE TROUGH AND
FRONT HAS CREATED WINDY CONDITIONS ACROSS MUCH OF THE FORECAST
AREA THIS MORNING. HAVE UPDATED FORECAST TO RAISE WINDS AND HIGH
TEMPERATURES AND TO ADJUST THE CLOUD COVER.
&&
.AVIATION...GUSTY SOUTHWEST WINDS WILL BECOME NORTHWEST TODAY. VFR
CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD.
&&
.PREV DISCUSSION... /ISSUED 243 AM MST SAT NOV 21 2009/
DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK LOW OVER NORTHEASTERN
WY. FAIRLY TIGHT GRADIENT NEAR LOW WITH GUSTY WINDS IN WY AND
PORTIONS OF THE BLACK HILLS ABOVE THE INVERSION. WILL LEAVE
ADVISORY IN PLACE UNTIL 600 AM. FOR TODAY...UPPER TROUGH OVER THE
ROCKIES MOVES EAST DRAGGING COLD FRONT THROUGH THE CWA...WASHING
OUT LATE. MOST HIGHS WILL OCCUR THIS MORNING WITH WEAK COLD AIR
ADVECTION IN THE AFTERNOON. FOR TONIGHT...WEAK HIGH SLIPS THROUGH.
HAVE DROPPED POPS GIVEN DRY NATURE OF LOWER TROPOSPHERE.
SUNDAY...VERY TRANSIENT SHORTWAVE RIDGE OVER THE CWA WILL GIVE WAY
TO FAST MOVING SHORTWAVE SUNDAY NIGHT. SURFACE HIGH QUICKLY SHIFTS
SOUTH WITH RETURN FLOW OVER WESTERN PORTIONS OF THE CWA. DRY
DURING THE DAY...BUT ENOUGH FORCING/MOISTURE PRESENT FOR LOW POPS
SUNDAY NIGHT. TEMPERATURES NEAR GUIDANCE.
MONDAY...SOME DIFFERENCES IN MODEL HANDLING OF SHORTWAVE TROUGH.
00Z NAM/ECMWF/GEM TRENDING SOUTH AND EAST. 00Z GFS MORE NORTHERLY
TRACK. WILL GO WITH MODEL TRENDS AT THIS POINT...WHICH WILL KEEP
BEST PRECIPITATION AWAY FROM THE CWA.
EXTENDED...AFOREMENTIONED SYSTEM WILL CONTINUE ITS DEPARTURE ON
TUESDAY...WITH SOME PRECIP POSSIBLY LINGERING OVER SOUTH CENTRAL
SOUTH DAKOTA. GFS BRINGS NEXT WAVE THROUGH THE REGION TUESDAY
NIGHT...THOUGH HAS HAD SOME TROUBLE WITH THE PLACEMENT OF THIS
SYSTEM OVER THE PAST FEW RUNS. THEREFORE...HAVE LIMITED LOW POPS
TO THE EASTERN/NRN CWFA. RIDGE STARTS BUILDING IN FOR MID-WEEK
BRINGING A RETURN TO DRY CONDITIONS.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
[top]
000
FXUS63 KFSD 211603
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1002 AM CST SAT NOV 21 2009
.DISCUSSION...
GOING FORECAST IN PRETTY GOOD SHAPE. VALLEY AREAS IN THE SOUTHEAST
CWA SLOWER TO SEE TEMPERATURE RECOVERY THIS MORNING...BUT THIS
HANDLED WELL IN THE GRIDS. LOWEST VISIBILITY FOG JUST SKIRTED BY THE
SOUTHEAST CORNER OF THE CWA. ANOTHER AREA OF FOG IN WESTERN IOWA
TRYING TO WORK NORTH INTO OUR SOUTHEAST CORNER...THOUGH NOW FIGHTING
WARMING TEMPERATURES WITH FULL SUNSHINE SO THINK IT WILL HAVE
DIFFICULTY MAKING ANY NORTHWARD PROGRESS. STRATUS FARTHER WEST WILL
BE STREAMING NORTHWARD THROUGH THE DAY AND WILL HAVE TO WATCH FOR
FASTER PROGRESS OF THIS INTO SOUTHERN CWA. SIMILAR TO THE FOG
THOUGH...NORTHERN END SEEMS TO BE ERODING A BIT SO WIDESPREAD
STRATUS SHOULD HOLD OFF UNTIL AFTER DARK. HOWEVER...IF STRATUS DOES
WORK INTO SOUTHERN AREAS...COULD HAVE DIFFICULTY REACHING HIGHS IN
THE UPPER 50S. WILL MONITOR TO SEE IF INCREASED MIXING HELPS
OVERCOME...BUT NO UPDATES TO GOING ZFP PLANNED FOR NOW.
&&
.AVIATION...
GENERALLY...CONDS WL BE VFR THRU TODAY AND EARLY THIS EVENING.
INCREASING SOUTH WINDS WILL BRING DEEPER LOW LEVEL MOISTURE INTO THE
AREA AFTER SUNSET...WITH MVFR-LOCALLY IFR CIGS/VSBYS IN BR EXPECTED
INTO KSUX AREA AFTER 02Z/03Z...SPREADING NORTH ALONG AND EAST OF
INTERSTATE 29 THROUGH 09Z. MVFR CIGS LIKELY TO PERSIST OVER EASTERN
PORTIONS OF THE FORECAST AREA...GENERALLY EAST OF KMML-KFSD-KYKN
LINE THROUGH 00Z MONDAY.
&&
.PREV DISCUSSION...
MORE ACTIVE PATTERN SETTING UP ACROSS THE AREA WITH SPLIT JET ACROSS
THE US. AREA OF LOW PRESSURE SHIFTING EAST INTO WESTERN
SASKATCHEWAN. AS THIS SYSTEM SHIFTS EAST...PRESSURE GRADIENT IS
EXPECTED TO INCREASE RESULTING IN FAIRLY STRONG SOUTHERLY FLOW
ACROSS THE NORTHERN PLAINS. FAIRLY MOIST AIR MASS POISED JUST SOUTH
OF FORECAST AREA...WITH WIDESPREAD FOG ACROSS EASTERN KANSAS AND
IOWA. AS SOUTHERLY WINDS INCREASE...EXPECT MOISTURE TO SURGE
NORTHWARD ESPECIALLY EAST OF INTERSTATE 29. WITH 925 HPA TEMP
WARMING INTO THE UPPER SINGLE DIGITS...HIGH TEMPERATURES TODAY
SHOULD BE NEARLY 20 DEGREES ABOVE NORMAL WITH HIGHS IN THE UPPER
50S. COULD SEE A FEW CLOUDS AND POTENTIAL FOR HAZE THIS AFTERNOON
TRICKLE INTO NORTHWEST IOWA WITH INCREASE IN MOISTURE...BUT DO NOT
THINK THIS WILL HAMPER WARMING TOO MUCH. WITH MILD
TEMPERATURES...STRONG SOUTHERLY WINDS AND DRY FUELS...WILL ISSUE
RANGE LAND FIRE STATEMENT FOR ELEVATED FIRE DANGER TODAY.
LOW LEVEL AIR MASS BECOMES SATURATED FAIRLY QUICKLY THIS EVENING
ACROSS IOWA EXPANDING BACK TO THE NORTH AND WEST OVERNIGHT.
SATURATION ONLY EXTENDS TO AROUND 900 MB OR SO...BUT WOULD NOT BE
SURPRISED TO SEE FOG ACROSS NORTHWEST IOWA EXPAND NORTH AND WEST
INTO SOUTHWEST MINNESOTA AND FAR SOUTHEASTERN SOUTH DAKOTA
OVERNIGHT. THERE IS ALSO A CHANCE OF DRIZZLE...BUT WITH LACK OF
STRONG LIFT AND STRONG DIRECTIONAL SHEAR ABOVE THE SATURATED
LAYER....KEPT POPS BELOW 15 PERCENT THROUGH 12Z SUNDAY.
THEREAFTER...DURING THE DAYTIME HOURS ON SUNDAY...EASTERN HALF OF
FORECAST AREA BECOMES POSITIONED IN RIGHT REAR OF UPPER LEVEL JET
STREAK. WHILE THE JET STREAK IS NOT OVERLY STRONG...MAY BE ENOUGH
TO INDUCE SOME LIGHT DRIZZLE AHEAD OF COLD FRONT ASSOCIATED WITH
AFOREMENTIONED LOW PRESSURE SYSTEM ACROSS CENTRAL CANADA. FLOW
REALLY BECOMES PARALLEL TO THE FRONT DURING THE EARLY MORNING HOURS
ON SUNDAY...AND FRONT IS EXPECTED TO HANG UP IN THE VICINITY OF THE
JAMES RIVER VALLEY. WITH RELATIVELY WEAK FLOW DURING THE DAY ON
SUNDAY...MAY BE A STRUGGLE TO SHAKE LOW LEVEL CLOUD COVER THROUGH
MUCH OF THE DAY...ESPECIALLY AHEAD OF THE FRONT. AS A RESULT...ONLY
WENT SLIGHTLY ABOVE ISOTHERMAL FROM 925 MB IN THE EAST...WHILE
EXPECT DEEPER MIXING TO THE WEST.
AS UPPER LEVEL TROUGH DIGS INTO THE PACIFIC NORTHWEST ON
SUNDAY...EXPECT INVERTED TROUGH TO SET UP AND AFFECT THE REGION
THROUGH WEDNESDAY MORNING. MODELS HAVE BEEN ALL OVER THE MAP IN
TERMS OF A TRACK WITH THIS SYSTEM...HOWEVER...00Z NAM...00Z ECMWF
AND 00Z CANADIAN IN FAIRLY GOOD AGREEMENT WITH DIGGING THIS SYSTEM
WEST OF UPPER MIDWEST TAKING THE CRUX OF THE WAVE SOUTH OF FORECAST
AREA. GFS IS NOT AS QUICK TO DIG THE SYSTEM...AND AS A RESULT BRINGS
THE SYSTEM FURTHER TO THE NORTH. FOR NOW..SIDED CLOSER TO THE
ECMWF/NAM/CANADIAN. MODELS PORTEND MOISTURE TRANSPORT SUNDAY NIGHT
INTO MONDAY EAST OF THE JAMES RIVER VALLEY. NOT REALLY A GREAT
FOCUSING MECHANISM...SO FOR NOW...JUST LEFT POPS IN THE LOW CHANCE
RANGE.
AS THE FRONT WORKS THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...EXPECT A WIDE VARIETY OF TEMPERATURES AND AS A RESULT IN
PRECIP TYPES. APPEARS AS THOUGH BEST DYNAMICS MAY BE FOCUSED ALONG
AND BEHIND OF INVERTED TROUGH...AND HAVE FOCUSED HIGHEST POPS THERE.
TRIED TO USE TEMPERATURES ALOFT FROM THE NAM IN A TOP DOWN
FORECASTING METHOD OF PRECIP TYPE...HOWEVER...THAT RESULTED IN A
FAIR AMOUNT OF FREEZING RAIN MONDAY NIGHT INTO TUESDAY. WHILE ONE
CAN NOT RULE OUT FREEZING RAIN WITH THIS SET UP...BELIEVE IT WOULD
BE MORE OF A TRANSITIONARY PRECIP TYPE AS OPPOSED TO A PREDOMINANT
TYPE AND THEREFORE LEFT OUT OF THE FORECAST FOR NOW. AGREE WITH
PREVIOUS FORECASTERS ASSESSMENT THAT BEST CHANCES FOR SNOW APPEAR TO
BE ACROSS CENTRAL SOUTH DAKOTA...SHIFTING EASTWARD TUESDAY NIGHT AS
THE SYSTEM SHIFTS EAST. /BT
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
JH
000
FXUS63 KABR 211554 AAA
AFDABR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
954 AM CST SAT NOV 21 2009
.UPDATE...
JUST SOME HIGH CIRRUS ASSOCIATED WITH A 250HPA JET-STREAK STREAMING
INTO THE REGION FROM THE SOUTHWEST. THE ONLY CHANGES MADE TO THE
TODAY PERIOD FORECAST WERE TO INCREASE CLOUD COVER A BIT FOR SOME
OF THIS THICKER CIRRUS EXPECTED TO BE AROUND TODAY...AND TO
INCREASE THE SOUTHERLY SURFACE WINDS TO ENSURE 20 TO 30 MPH WITH
GUST TO 40 MPH WORDING SHOWED UP...SINCE THE RUC SHOWS 35 TO 40
KNOT WINDS AT APPX 1000FT OFF THE SURFACE. WOULD THINK THAT
DAYTIME MIXING AND THE FORMIDABLE PRESSURE GRADIENT ACROSS THE
AREA WOULD BEGIN TAPPING INTO SOME OF THOSE STRONG WINDS BY EARLY
THIS AFTERNOON.
&&
.PREV DISCUSSION...
.SHORT TERM...TODAY THROUGH MONDAY
TODAY WILL BE BREEZY/WINDY ACROSS MUCH OF THE CWA AS PRESSURE
GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. 925/850
WINDS ON THE ORDER OF 40-50 KNOTS BUT DO NOT EXPECT WIND GUSTS TO
BE THIS HIGH. THE COLD FRONT TRACKS EAST ACROSS THE CWA
TONIGHT...BRINGING COOLER TEMPERATURES FOR SUNDAY. AFTER MUCH
ABOVE NORMAL TEMPS IN THE 50S TODAY...HIGHS WILL DROP BACK DOWN
INTO THE 40S FOR SUNDAY. WEAK SHORTWAVE MOVES THROUGH THE AREA ON
SUNDAY BUT BEST MOISTURE AVAILABILITY REMAINS EAST OF THE REGION
IN MN SO WILL KEEP FORECAST DRY. ATTENTION THEN TURNS TO THE
APPROACHING STORM SYSTEM WHICH BEGINS TO AFFECT THE REGION LATE
SUNDAY NIGHT AND MONDAY. GFS REMAINS THE FURTHEST NORTH OF ALL
MODELS AND IS QUICKER...BUT HAS SHOWN A NOTICEABLE TREND TO THE
SOUTH...TRYING TO COME IN LINE MORE WITH THE MORE CONSISTENT EC
AND CANADIAN SOLUTIONS...WHICH HAVE ALWAYS BEEN FURTHER SOUTH. THE
NEW 00Z EC IS EVEN A TAD FURTHER SOUTH THAN ITS PREVIOUS RUN BUT
WHATS INTERESTING IS THAT IT HAS DEVELOPED A MORE PRONOUNCED
INVERTED TROUGH WHICH NOSES NORTHWARD ALONG THE SD/MN BORDER. THIS
COULD SPELL OUT DECENT PRECIP CHANCES THIS FAR NORTH...EVEN THOUGH
MAIN SFC LOW IS WELL SOUTH OF THE AREA. WILL HAVE TO KEEP AN EYE
ON THIS DEVELOPMENT. THERMAL PROFILES STILL SUGGEST MOSTLY RAIN TO
START OFF...THEN CHANGING OVER TO SNOW FROM WEST TO EAST TOWARDS
THE END OF THE EVENT. HAVE NOT MADE REAL SIGNIFICANT CHANGES TO
WX/POPS DURING THE SHORT TERM PERIOD.
.LONG TERM...MONDAY NIGHT THROUGH FRIDAY
A SOMEWHAT ACTIVE PATTERN STILL APPEARS ON TAP FOR THE FIRST PART
OF THE LONG TERM. ALL MODELS STILL PRODUCE A DECENT LOOKING YET
PROGRESSIVE UPPER LOW OVER THE CENTRAL/NORTHERN PLAINS THROUGH MID
WEEK. THE ECMWF REMAINS THE SLOWEST AND FURTHEST SOUTH OF ALL
DETERMINISTIC 00Z RUNS. MEANWHILE THE GEM HAS TRENDED TOWARD THE
GFS. WITH SOME UNCERTAINTY IN THE FORECAST...FELT THAT THE BEST
POLICY WAS TO STAY SOMEWHAT CLOSE TO THE INHERITED SOLUTION. RAIN
AND SNOW WILL BE POSSIBLE INTO TUESDAY BEFORE BECOMING MOSTLY SNOW
BY TUESDAY NIGHT. IT APPEARS THE HIGHEST PCPN PROBABILITIES WILL
EXIST OVER THE BIG SIOUX VALLEY/SISSETON HILLS WHERE AN INVERTED
TROF MAY HANG OUT FOR 24 HOURS OR MORE. TEMPERATURES WERE ONLY
MODIFIED SLIGHTLY AFTER LOOKING AT THE LATEST LONG RANGE TEMP PROGS.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL TODAY WITH SCT-BKN HIGH CLOUDS AOA 15K
FEET STREAMING ACROSS THE REGION. SOUTHERLY WINDS OF 15 TO 30 MPH
WILL BE COMMON DURING THE DAYLIGHT HOURS...THEN WILL DIMINISH TO
LESS THAN 10 MPH AFTER SUNSET.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...DORN
SHORT TERM...TMT
LONG TERM...TDK
AVIATION...PARKIN
WEATHER.GOV/ABERDEEN
000
FXUS63 KFSD 211015
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
410 AM CST SAT NOV 21 2009
.DISCUSSION...
MORE ACTIVE PATTERN SETTING UP ACROSS THE AREA WITH SPLIT JET ACROSS
THE US. AREA OF LOW PRESSURE SHIFTING EAST INTO WESTERN
SASKATCHEWAN. AS THIS SYSTEM SHIFTS EAST...PRESSURE GRADIENT IS
EXPECTED TO INCREASE RESULTING IN FAIRLY STRONG SOUTHERLY FLOW
ACROSS THE NORTHERN PLAINS. FAIRLY MOIST AIR MASS POISED JUST SOUTH
OF FORECAST AREA...WITH WIDESPREAD FOG ACROSS EASTERN KANSAS AND
IOWA. AS SOUTHERLY WINDS INCREASE...EXPECT MOISTURE TO SURGE
NORTHWARD ESPECIALLY EAST OF INTERSTATE 29. WITH 925 HPA TEMP
WARMING INTO THE UPPER SINGLE DIGITS...HIGH TEMPERATURES TODAY
SHOULD BE NEARLY 20 DEGREES ABOVE NORMAL WITH HIGHS IN THE UPPER
50S. COULD SEE A FEW CLOUDS AND POTENTIAL FOR HAZE THIS AFTERNOON
TRICKLE INTO NORTHWEST IOWA WITH INCREASE IN MOISTURE...BUT DO NOT
THINK THIS WILL HAMPER WARMING TOO MUCH. WITH MILD
TEMPERATURES...STRONG SOUTHERLY WINDS AND DRY FUELS...WILL ISSUE
RANGE LAND FIRE STATEMENT FOR ELEVATED FIRE DANGER TODAY.
LOW LEVEL AIR MASS BECOMES SATURATED FAIRLY QUICKLY THIS EVENING
ACROSS IOWA EXPANDING BACK TO THE NORTH AND WEST OVERNIGHT.
SATURATION ONLY EXTENDS TO AROUND 900 MB OR SO...BUT WOULD NOT BE
SURPRISED TO SEE FOG ACROSS NORTHWEST IOWA EXPAND NORTH AND WEST
INTO SOUTHWEST MINNESOTA AND FAR SOUTHEASTERN SOUTH DAKOTA
OVERNIGHT. THERE IS ALSO A CHANCE OF DRIZZLE...BUT WITH LACK OF
STRONG LIFT AND STRONG DIRECTIONAL SHEAR ABOVE THE SATURATED
LAYER....KEPT POPS BELOW 15 PERCENT THROUGH 12Z SUNDAY.
THEREAFTER...DURING THE DAYTIME HOURS ON SUNDAY...EASTERN HALF OF
FORECAST AREA BECOMES POSITIONED IN RIGHT REAR OF UPPER LEVEL JET
STREAK. WHILE THE JET STREAK IS NOT OVERLY STRONG...MAY BE ENOUGH
TO INDUCE SOME LIGHT DRIZZLE AHEAD OF COLD FRONT ASSOCIATED WITH
AFOREMENTIONED LOW PRESSURE SYSTEM ACROSS CENTRAL CANADA. FLOW
REALLY BECOMES PARALLEL TO THE FRONT DURING THE EARLY MORNING HOURS
ON SUNDAY...AND FRONT IS EXPECTED TO HANG UP IN THE VICINITY OF THE
JAMES RIVER VALLEY. WITH RELATIVELY WEAK FLOW DURING THE DAY ON
SUNDAY...MAY BE A STRUGGLE TO SHAKE LOW LEVEL CLOUD COVER THROUGH
MUCH OF THE DAY...ESPECIALLY AHEAD OF THE FRONT. AS A RESULT...ONLY
WENT SLIGHTLY ABOVE ISOTHERMAL FROM 925 MB IN THE EAST...WHILE
EXPECT DEEPER MIXING TO THE WEST.
AS UPPER LEVEL TROUGH DIGS INTO THE PACIFIC NORTHWEST ON
SUNDAY...EXPECT INVERTED TROUGH TO SET UP AND AFFECT THE REGION
THROUGH WEDNESDAY MORNING. MODELS HAVE BEEN ALL OVER THE MAP IN
TERMS OF A TRACK WITH THIS SYSTEM...HOWEVER...00Z NAM...00Z ECMWF
AND 00Z CANADIAN IN FAIRLY GOOD AGREEMENT WITH DIGGING THIS SYSTEM
WEST OF UPPER MIDWEST TAKING THE CRUX OF THE WAVE SOUTH OF FORECAST
AREA. GFS IS NOT AS QUICK TO DIG THE SYSTEM...AND AS A RESULT BRINGS
THE SYSTEM FURTHER TO THE NORTH. FOR NOW..SIDED CLOSER TO THE
ECMWF/NAM/CANADIAN. MODELS PORTEND MOISTURE TRANSPORT SUNDAY NIGHT
INTO MONDAY EAST OF THE JAMES RIVER VALLEY. NOT REALLY A GREAT
FOCUSING MECHANISM...SO FOR NOW...JUST LEFT POPS IN THE LOW CHANCE
RANGE.
AS THE FRONT WORKS THROUGH THE AREA MONDAY NIGHT INTO
TUESDAY...EXPECT A WIDE VARIETY OF TEMPERATURES AND AS A RESULT IN
PRECIP TYPES. APPEARS AS THOUGH BEST DYNAMICS MAY BE FOCUSED ALONG
AND BEHIND OF INVERTED TROUGH...AND HAVE FOCUSED HIGHEST POPS THERE.
TRIED TO USE TEMPERATURES ALOFT FROM THE NAM IN A TOP DOWN
FORECASTING METHOD OF PRECIP TYPE...HOWEVER...THAT RESULTED IN A
FAIR AMOUNT OF FREEZING RAIN MONDAY NIGHT INTO TUESDAY. WHILE ONE
CAN NOT RULE OUT FREEZING RAIN WITH THIS SET UP...BELIEVE IT WOULD
BE MORE OF A TRANSITIONARY PRECIP TYPE AS OPPOSED TO A PREDOMINANT
TYPE AND THEREFORE LEFT OUT OF THE FORECAST FOR NOW. AGREE WITH
PREVIOUS FORECASTERS ASSESSMENT THAT BEST CHANCES FOR SNOW APPEAR TO
BE ACROSS CENTRAL SOUTH DAKOTA...SHIFTING EASTWARD TUESDAY NIGHT AS
THE SYSTEM SHIFTS EAST. /BT
&&
.AVIATION...
GENERALLY...CONDS WL BE VFR THRU TODAY AND THIS EVENING. THE
EXCEPTION WL BE THIS MORNING...WHERE AREAS OF MVFR VIS WL OCCUR THRU
15Z MOSTLY EAST OF I 29. WATCHING THE MORE DENSE FOG LIFT NORTH TO
NORTHEASTWARD EARLY THIS MORNING FM SW IA...IT IS POSSIBLE THAT
AREAS AROUND STORM LAKE IA MAY GET CLIPPED WITH CONDS OF LIFR EARLY
TODAY. BUT AGAIN...IF THOSE CONDS OCCUR...THEY SHOULD BE CONFINED
ONLY TO THE SE CORNER OF THE FSD FORECAST AREA. /MJF
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KABR 210950
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
350 AM CST SAT NOV 21 2009
.SHORT TERM...TODAY THROUGH MONDAY
TODAY WILL BE BREEZY/WINDY ACROSS MUCH OF THE CWA AS PRESSURE
GRADIENT TIGHTENS AHEAD OF AN APPROACHING COLD FRONT. 925/850
WINDS ON THE ORDER OF 40-50 KNOTS BUT DO NOT EXPECT WIND GUSTS TO
BE THIS HIGH. THE COLD FRONT TRACKS EAST ACROSS THE CWA
TONIGHT...BRINGING COOLER TEMPERATURES FOR SUNDAY. AFTER MUCH
ABOVE NORMAL TEMPS IN THE 50S TODAY...HIGHS WILL DROP BACK DOWN
INTO THE 40S FOR SUNDAY. WEAK SHORTWAVE MOVES THROUGH THE AREA ON
SUNDAY BUT BEST MOISTURE AVAILABILITY REMAINS EAST OF THE REGION
IN MN SO WILL KEEP FORECAST DRY. ATTENTION THEN TURNS TO THE
APPROACHING STORM SYSTEM WHICH BEGINS TO AFFECT THE REGION LATE
SUNDAY NIGHT AND MONDAY. GFS REMAINS THE FURTHEST NORTH OF ALL
MODELS AND IS QUICKER...BUT HAS SHOWN A NOTICEABLE TREND TO THE
SOUTH...TRYING TO COME IN LINE MORE WITH THE MORE CONSISTENT EC
AND CANADIAN SOLUTIONS...WHICH HAVE ALWAYS BEEN FURTHER SOUTH. THE
NEW 00Z EC IS EVEN A TAD FURTHER SOUTH THAN ITS PREVIOUS RUN BUT
WHATS INTERESTING IS THAT IT HAS DEVELOPED A MORE PRONOUNCED
INVERTED TROUGH WHICH NOSES NORTHWARD ALONG THE SD/MN BORDER. THIS
COULD SPELL OUT DECENT PRECIP CHANCES THIS FAR NORTH...EVEN THOUGH
MAIN SFC LOW IS WELL SOUTH OF THE AREA. WILL HAVE TO KEEP AN EYE
ON THIS DEVELOPMENT. THERMAL PROFILES STILL SUGGEST MOSTLY RAIN TO
START OFF...THEN CHANGING OVER TO SNOW FROM WEST TO EAST TOWARDS
THE END OF THE EVENT. HAVE NOT MADE REAL SIGNIFICANT CHANGES TO
WX/POPS DURING THE SHORT TERM PERIOD.
.LONG TERM...MONDAY NIGHT THROUGH FRIDAY
A SOMEWHAT ACTIVE PATTERN STILL APPEARS ON TAP FOR THE FIRST PART
OF THE LONG TERM. ALL MODELS STILL PRODUCE A DECENT LOOKING YET
PROGRESSIVE UPPER LOW OVER THE CENTRAL/NORTHERN PLAINS THROUGH MID
WEEK. THE ECMWF REMAINS THE SLOWEST AND FURTHEST SOUTH OF ALL
DETERMINISTIC 00Z RUNS. MEANWHILE THE GEM HAS TRENDED TOWARD THE
GFS. WITH SOME UNCERTAINTY IN THE FORECAST...FELT THAT THE BEST
POLICY WAS TO STAY SOMEWHAT CLOSE TO THE INHERITED SOLUTION. RAIN
AND SNOW WILL BE POSSIBLE INTO TUESDAY BEFORE BECOMING MOSTLY SNOW
BY TUESDAY NIGHT. IT APPEARS THE HIGHEST PCPN PROBABILITIES WILL
EXIST OVER THE BIG SIOUX VALLEY/SISSETON HILLS WHERE AN INVERTED
TROF MAY HANG OUT FOR 24 HOURS OR MORE. TEMPERATURES WERE ONLY
MODIFIED SLIGHTLY AFTER LOOKING AT THE LATEST LONG RANGE TEMP PROGS.
&&
.AVIATION...
THROUGH TODAY VFR CONDITIONS WILL PREVAIL ALTHOUGH BLUSTERY WINDS
WILL ARRIVE SHORTLY AFTER DAYBREAK.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
SHORT TERM...TMT
LONG TERM...TDK
AVIATION...TDK
WEATHER.GOV/ABERDEEN
000
FXUS63 KUNR 210943
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
243 AM MST SAT NOV 21 2009
.DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK LOW OVER NORTHEASTERN
WY. FAIRLY TIGHT GRADIENT NEAR LOW WITH GUSTY WINDS IN WY AND
PORTIONS OF THE BLACK HILLS ABOVE THE INVERSION. WILL LEAVE
ADVISORY IN PLACE UNTIL 600 AM. FOR TODAY...UPPER TROUGH OVER THE
ROCKIES MOVES EAST DRAGGING COLD FRONT THROUGH THE CWA...WASHING
OUT LATE. MOST HIGHS WILL OCCUR THIS MORNING WITH WEAK COLD AIR
ADVECTION IN THE AFTERNOON. FOR TONIGHT...WEAK HIGH SLIPS THROUGH.
HAVE DROPPED POPS GIVEN DRY NATURE OF LOWER TROPOSPHERE.
SUNDAY...VERY TRANSIENT SHORTWAVE RIDGE OVER THE CWA WILL GIVE WAY
TO FAST MOVING SHORTWAVE SUNDAY NIGHT. SURFACE HIGH QUICKLY SHIFTS
SOUTH WITH RETURN FLOW OVER WESTERN PORTIONS OF THE CWA. DRY
DURING THE DAY...BUT ENOUGH FORCING/MOISTURE PRESENT FOR LOW POPS
SUNDAY NIGHT. TEMPERATURES NEAR GUIDANCE.
MONDAY...SOME DIFFERENCES IN MODEL HANDLING OF SHORTWAVE TROUGH.
00Z NAM/ECMWF/GEM TRENDING SOUTH AND EAST. 00Z GFS MORE NORTHERLY
TRACK. WILL GO WITH MODEL TRENDS AT THIS POINT...WHICH WILL KEEP
BEST PRECIPITATION AWAY FROM THE CWA.
EXTENDED...AFOREMENTIONED SYSTEM WILL CONTINUE ITS DEPARTURE ON
TUESDAY...WITH SOME PRECIP POSSIBLY LINGERING OVER SOUTH CENTRAL
SOUTH DAKOTA. GFS BRINGS NEXT WAVE THROUGH THE REGION TUESDAY
NIGHT...THOUGH HAS HAD SOME TROUBLE WITH THE PLACEMENT OF THIS
SYSTEM OVER THE PAST FEW RUNS. THEREFORE...HAVE LIMITED LOW POPS
TO THE EASTERN/NRN CWFA. RIDGE STARTS BUILDING IN FOR MID-WEEK
BRINGING A RETURN TO DRY CONDITIONS.
&&
.AVIATION...GUSTY SOUTHWEST WINDS OVER THE NRN AND NERN FOOTHILLS OF
THE BLKHLS AND OVER NERN WY WILL DIMINISH THIS MORNING. VFR
CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 6 AM MST EARLY THIS MORNING FOR NORTHERN
FOOT HILLS-STURGIS/PIEDMONT FOOT HILLS.
WY...NONE.
&&
$$
HELGESON/SCHILD
000
FXUS63 KUNR 210339
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
839 PM MST FRI NOV 20 2009
.DISCUSSION...SURFACE TROF MOVING THROUGH NORTHEAST WYOMING THIS
EVENING...WITH WINDS STARTING TO INCREASE. OVERALL...FORECAST IN
GOOD SHAPE. WILL UPDATE FORECAST TO INCREASE CLOUD COVER AS CIRRUS
SPREADS ACROSS THE AREA.
&&
.AVIATION...SOUTHWEST WINDS OF 20 TO 30 KTS WITH GUSTS TO 40 KTS
WILL DEVELOP ACROSS NORTHEAST WYOMING...THE NORTHERN BLACK
HILLS...AND NORTHERN FOOTHILLS TONIGHT. INVERSION WILL KEEP THE
WINDS FROM AFFECTING SFC WINDS AT KRAP...THOUGH LOW LEVEL WIND
SHEAR ADDED TO TAF TO ACCOUNT FOR THE 40KT WINDS AT 2000FT AGL. VFR
CONDITIONS CAN BE EXPECTED THROUGH SATURDAY MORNING.
&&
.PREV DISCUSSION... /ISSUED 240 PM MST FRI NOV 20 2009/
DISCUSSION...21Z SFC ANALYSIS SHOWS LEE SIDE TROUGH EXTENDING
FROM A LOW PRESSURE CENTER OVER ALBERTA INTO EASTERN WYOMING AND
EASTERN COLORADO. UPPER ANALYSIS SHOWS RIDGING OVER THE NORTHERN
PLAINS WITH A TROUGH MOVING ONTO THE WEST COAST.
THE PRESSURE GRADIENT WILL TIGHTEN TONIGHT AS THE SFC TROUGH
MOVES SLOWLY EAST INTO WESTERN SOUTH DAKOTA. GUSTY SOUTHWESTERLY
WINDS WILL DEVELOP WEST OF THE TROUGH AXIS OVER NORTHEASTERN
WYOMING THIS EVENING. PRESSURE GRADIENT ANALYSIS ALSO SHOWS THE
POTENTIAL FOR GUSTY SOUTHWESTERLY DOWNSLOPE WINDS TO DEVELOP OVER
THE NORTHERN BLACK HILLS AND THE ADJACENT FOOTHILLS TONIGHT.
FORECAST WINDS ALOFT SHOW THAT GUSTS AS HIGH AS 50 MPH WILL BE
POSSIBLE IN THOSE AREAS OVERNIGHT SO HAVE ISSUED A WIND ADVISORY
FOR THE NORTHERN AND NORTHEASTERN FOOTHILLS OF THE BLACK HILLS
TONIGHT.
ON SATURDAY...THE UPPER TROUGH APPROACHES FROM THE WEST...PUSHING
A COLD FRONT INTO NORTHEASTERN WYOMING AND NORTHWESTERN SOUTH
DAKOTA BY MIDDAY...THEN CROSSING THE REST OF THE AREA SATURDAY
AFTERNOON AND EVENING. THE FRONT WILL USHER IN COOLER AIR WITH
LIMITED MOISTURE. WILL CONTINUE LOW POPS IN THE WEST NEAREST BEST
FORCING.
ON SUNDAY...THE SURFACE HIGH SHIFTS EAST WITH RETURN FLOW IN THE
WEST. NEXT SHORTWAVE SWINGS INTO THE REGION FOR LOW POPS SUNDAY
NIGHT. HIGH TEMPERATURES WILL BE NOTICEABLY COLDER SUNDAY...A RETURN
TO MORE SEASONAL CONDITIONS.
EXTENDED...GFS ENSEMBLE MEMBERS SHOWING GOOD AGREEMENT ON SWINGING
TROUGH THROUGH THE CWA ON MONDAY. ECMWF AND GEM OPERATIONAL RUNS
ALSO CONSISTENT WITH THESE SOLUTIONS. THE ECMWF AND GEM RUNS DIVERGE
FROM GFS GOING INTO MONDAY NIGHT...WRAPPING UP AN UPPER LOW ALONG
THE NEBRASKA AND KANSAS BORDER. RMOP INDICATING LOWER PREDICTABILITY
WITH THIS SYSTEM. WILL KEEP CHANCE POPS ACROSS SOUTH CENTRAL
PORTIONS OF THE CWA ATTM MONDAY INTO TUESDAY. HAVE BUMPED TEMPS DOWN
ACROSS THE CWA UNDER COOL NORTHWEST FLOW.
THE GFS SHOWS ANOTHER WAVE SWEEPING ACROSS THE CWA TUESDAY NIGHT
INTO WEDNESDAY. NEITHER GEM NOR ECMWF AGREE WITH THIS SCENARIO.
SEVERAL GFS ENSEMBLE MEMBERS POINTING TO THIS SOLUTION...SO WILL
KEEP SLIGHT CHANCE POPS ACROSS THE CWA FOR THIS TIMEFRAME. MODELS
CONSISTENT WITH BUILDING RIDGE ACROSS THE WESTERN CONUS THURSDAY
INTO FRIDAY AHEAD OF NEXT TROUGH. ATTM IT APPEARS THAT THE CWA WILL
BE DRY GOING INTO LATE NEXT WEEK.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY UNTIL 6 AM MST SATURDAY FOR NORTHERN FOOT HILLS-
STURGIS/PIEDMONT FOOT HILLS.
WY...NONE.
&&
$$
000
FXUS63 KFSD 210241
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
830 PM CST FRI NOV 20 2009
.DISCUSSION...
TEMPERATURES DROPPING OFF QUICKLY IN OUR EAST THIS EVENING WITH
WINDS NEARLY CALM...AND HAD TO DROP MINS A COUPLE OF DEGREES IN THE
LOWEST ELEVATIONS. EXPECT TEMPERATURES TO STEADY OUT OR EVEN A RISE
A BIT OVERNIGHT WITH WINDS PICKING UP IN A TIGHTENING GRADIENT...AND
HIGH TO MID CLOUDS ROUNDING THE CENTRAL U.S. RIDGE. MINOR UPDATES
OUT WITH NO CHANGE TO ZFP. /JM
&&
.PREV DISCUSSION...
QUIET NIGHT ACROSS THE AREA AS WINDS GRADUALLY SWING AROUND TO THE
SOUTH AND SOUTHEAST AND INCREASE...ESPECIALLY OVER THE WEST. WENT
WITH NON DIURNAL TEMPERATURES ALONG AND WEST OF THE JAMES RIVER AS
WINDS BEGIN TO INCREASE MORE STEADILY. EVEN HAVE TEMPERATURES RISING
A LITTLE TOWARDS 12Z IN THE FAR EAST. OTHERWISE...DECREASED LOWS A
LITTLE FROM ABOUT INTERSTATE 29 EAST WITH LIGHT FLOW AND CLEAR SKIES
THROUGH MUCH OF THE NIGHT. LOWS SHOULD RANGE FROM THE MID TO UPPER
20S EAST OF INTERSTATE 29 TO THE LOWER 30S WEST OF THE JAMES RIVER.
SATURDAY SHOULD PROVE TO BE A MILD BUT BREEZY DAY AS WINDS INCREASE
TO SOMETHING AROUND 20 TO 30 MPH ON A STRONG SOUTHERLY GRADIENT.
MOISTURE ALSO SET TO INCREASE ALONG INCOMING LLJ SO HAVE PARTLY TO
MOSTLY CLOUDY SKIES IN THE EAST DURING THE AFTERNOON. QUIET A BIT OF
MOISTURE RETURN JUST OFF THE SFC AND THIS LOOKS REASONABLE GIVEN
HIGHER DEW POINT AIR IN EASTERN OKLAHOMA. HIGHS MAINLY IN THE 50S.
SATURDAY NIGHT WILL SEE A WIND SHIFT WORK INTO THE AREA AHEAD OF AN
ENTRANCE REGION TO A RELATIVELY WEAK UPPER LEVEL JET STREAK. MAY BE
JUST ENOUGH LIFT ALOFT AND JUST ENOUGH MOISTURE CONVERGENCE IN THE
LOW TO MID LEVELS TO SUPPORT A LITTLE LIGHT RAIN OVER THE EASTERN
CWA...BUT WILL HOLD OFF ON BETTER CHANCES UNTIL SUNDAY. EXPECT
CLOUDS TO ALSO INCREASE DURING THIS TIME AS THE UPPER WAVE
APPROACHES THE DECENT LOW TO MID LEVEL MOISTURE. LOWS WILL BE
MILD...ESPECIALLY IN THE EAST WHERE THE STRONGER SOUTHERLY FLOW
REMAINS IN PLACE...AND SHOULD RANGE FROM THE LOWER 40S IN NW IA TO
30 TO 35 IN CENTRAL SD.
AS STATED EARLIER...WILL MAINTAIN SOME LOWER END POPS IN THE EAST
FOR A FEW RAIN SHOWERS WITH INCOMING WEAK ENTRANCE REGION AND WEAK
MID TO LOW LEVEL MOISTURE CONVERGENCE. THIS SHOULD KEEP CLOUD COVER
IN PLACE MUCH OF THE DAY...BUT DECREASE SLOWLY FROM WEST TO EAST. A
LITTLE COOLER BUT A LOT LESS WIND SO STILL MILD...WITH HIGHS FROM
THE UPPER 40S TO LOWER 50S. /08
HEADING INTO SUNDAY NIGHT...AFTER SOME HINT OF A DYNAMIC DOWNTIME
AFTER WAVE SHEARS BY TO THE NORTHEAST...THE TRAILING SYSTEM STARTS
TO INCREASE LOW LVL FLOW AGAIN WITH ISENTROPIC TRANSPORT INCREASING
THRU THE CWA FROM S TO N. A LITTLE LOWER TO MID LVL CONVERGENCE
AXIS LOOKS TO SET UP FROM SW TO NE ACRS THE AREA LIFTING SLOWLY
NE...AND ENOUGH TO PERHAPS FOCUS A SMALL POP LATER IN THE NIGHT.
THE INCREASING SELY FLOW...CLOUDS...AND MOISTURE LKLY TO KEEP TMPS
WARM ENOUGH AT TIME OF PCPN THREAT FOR ALL RAIN...BUT ANY QUICKER
APPROACH WOULD PERHAPS BRING SOME LIGHT FREEZING RAIN TO THE MIX.
MONDAY GETS SOME BETTER DIV Q IN THE MIX ADVANCING OUT AHEAD OF THE
TROUGH DIGGING INTO THE CNTRL/SRN PLAINS. MAIN MID LVL
BNDRY/CONVERGENCE STARTS TO LOCK INTO THE NRN/SWRN CWA...AND WOULD
SEEM TO BE A SLIGHTLY BETTER FOCUS FOR MID TO HIGH CHC POPS. START
TO LIMIT DIURNAL RANGE SOMEWHAT MORE WITH HIGH AMT OF CLDS.
FOR THE EXTENDED RANGE /MON NIGHT THRU FRI/ ALMOST FUNNY HOW CHANGES
IN THE LONG RANGE GUIDANCE...ESPECIALLY AFFECTING THE START OF THE
PERIOD...WAS PREDICTABLE. FOR THE MOST PART THE VARIOUS CAMPS HAVE
NOT ABANDONED THEIR RESPECTIVE SLNS...WITH GFS CONTINUING AS THE
PROGRESSIVE POSTER CHILD...BUT THE CANADIAN/ECMWF/UKMET ALL ON THE
SLOW AND DIGGY SIDE...WITH 12Z RUNS OF THE FORMER PAIR EVEN MORESO.
ENCOURAGING WAS GFS HALF STEP BACK TOWARD MORE DIGGING. THEREFORE...
HARD TO DENY THAT THERE WILL NOT BE A PRECIPITATION EVENT IN THE
MONDAY NIGHT TO TUESDAY NIGHT WINDOW /ALTHOUGH LATEST GUIDANCE
TRENDS WOULD PERHAPS PUSH BACK A PERIOD OR SO FOR BEST FORCING/.
INTRODUCED SOME LKLY POPS THRU THE NWRN HALF OF THE CWA FOR THE
MOMENT...TAPERING OFF SLIGHTLY TOWARD THE FAR SE. WRAPPED UP LOWS
NOTORIOUS FOR SLOW PROGRESSION AND LOOKS TO BE ONE WHERE AN EVENTUAL
TROWAL STRUCTURE IS PROBABLE...ALONG WITH A HEALTHY INVERTED
TROUGH...FAVORING PCPN ALG/BEHIND. THESE TYPES OF SYSTEM ALSO SEEM
TO HAVE A TENDENCY TO BRING UP WARMER AND MOIST AIR...WRAPPING WELL
WESTWARD FOR A WHILE. CERTAINLY THE BETTER OF THE SNOW THREAT WOULD
BE BACK ALG/W OF THE INVERTED TROUGH...AND DO NOT HAVE SUGGESTIONS
OF A DRIER ELY TRAJECTORY TO HELP WET BULB THINGS. THEREFORE...KEPT
ANY SNOW MENTION LIMITED TO THE EXTREME WEST...WITH MIX TOWARD THE
JAMES VALLEY MONDAY NIGHT...THEN ON A BIT EASTWARD TUE...BEFORE
STARTING A WHOLE SCALE CHANGEOVER TUE NIGHT. SOME LINGERING POPS
CONTINUED THRU THE NE/E ON WEDNESDAY.
THE END OF THE WEEK IS FEATURED DRY AT THIS POINT AS RIDGING
REBOUNDS THRU THE NRN PLAINS. SFC RIDGE MOVING OVER THU INTO EARLY
FRI COULD LEAD TO SOME CHILLY LOWS...ESPLY IF WRN AREAS HAVE ANY
DECENT SNOWCOVER. SOME COLD AIR SC MAY BE AROUND ON THU THRU ERN
CWA...BUT MAINLY CLEAR TO MO CLR EXPECTED BY THU NIGHT/FRI. FOR
NOW...DID NOT FULLY ACCEPT THE RAPIDITY OF THE WARMUP ON FRIDAY...
BUT WL BE SOMETHING TO WATCH FOR ONCE THE EVOLUTION OF THE EARLY TO
MID WEEK SYSTEM IS DEFINED. /CHAPMAN
&&
.AVIATION...
PRETTY MUCH VFR THROUGH 0Z SUNDAY. NOT OUT OF THE QUESTION TO SEE
SOME VALLEY FOG LATE TONIGHT...BUT COVERAGE SHOULD BE MINIMAL. WE
WILL SEE AN INFLUX OF MOISTURE ON SATURDAY AFTERNOON...WITH THE
POTENTIAL FOR HIGH END MVFR CEILINGS AT SUX...AND POSSIBLY FSD.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KABR 210206
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
806 PM CST FRI NOV 20 2009
.UPDATE...
NO CHANGES PLANNED FOR THE EVENING UPDATE. TEMPERATURES WERE QUICK
TO FALL INITIALLY AS USUAL UNDER CLEAR SKIES. EXPECT OVERNIGHT
LOWS WILL BE ALRIGHT AS SATELLITE LOOP SHOWS SOME MID AND HIGH
LEVEL CLOUDS APPROACHING FROM THE NORTHWEST. ALSO AS WIND STAYS
RATHER STRONG TONIGHT TEMPERATURES WILL NOT CONTINUE TO FALL AS
QUICKLY.
&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT
FORECAST CHALLENGES CONTINUE TO BE WIND SPEEDS ON SATURDAY AND
TEMPERATURES THROUGHOUT THE SHORT TERM.
CURRENTLY...HIGH PRESSURE AT THE SURFACE AND ALOFT OVER THIS CWA
IS CLAIMING RESPONSIBILITY FOR THE SUNNY SKY AND LIGHT WINDS.
TEMPERATURES ARE WORKING INTO THE UPPER 40S WITH A FEW LOCATIONS
ALREADY NUDGING UP INTO THE LOW 50S.
RETURN FLOW SETS UP ACROSS THE CWA TONIGHT AND PERSISTS RIGHT ON
THROUGH SATURDAY. SURFACE TO 925HPA WIND SPEEDS CONTINUE IN THE 15
TO 30 KNOT RANGE...SO BREEZY TO WINDY SOUTH WINDS STILL ON COURSE.
THE FIRST IN A SERIES OF LOW PRESSURE SYSTEMS WORKS THROUGH THE
FORECAST AREA SATURDAY AND SATURDAY NIGHT...DRAGGING A COLD FRONT
THROUGH THE CWA. THIS FIRST LOW WILL NOT HAVE ENOUGH MOISTURE TO
WORK WITH TO PRODUCE MEASURABLE PRECIPITATION. HOWEVER...RETURN
FLOW MOISTURE WORKING INTO THE REGION...MAY BE JUST ENOUGH TO
SUPPORT LOW STRATUS CLOUD FORMATION ACROSS THE FAR EASTERN
FORECAST AREA /KATY AND K8D3 AND KETH AND KVVV/ SATURDAY NIGHT
INTO SUNDAY. A SECOND AREA OF LOW PRESSURE /THE ONE BEING WATCHED
CLOSELY/ STARTS TO ENCROACH UPON THE CWA AND THE SHORT RANGE
FORECAST BY SUNDAY NIGHT...WITH SATURATION OF THE ATMOSPHERIC
COLUMN REALLY GETTING GOING SUNDAY NIGHT. FOR NOW...HAVE WORKED TO
COORDINATE APPX THE SWRN HALF OF THE CWA IN RATHER LOW-END POPS
SUNDAY NIGHT. FOLLOWING THE WINT WX TYPES PROCEDURE TO DETERMINE
P-TYPE...SUNDAY NIGHT TURNS OUT TO BE A POSSIBLE MIX OF RAIN/FRZNG
RAIN AND/OR SNOW...ESPECIALLY ACROSS THE SOUTHEASTERN FORECAST
ZONES.
TEMPERATURES THROUGHOUT THE SHORT TERM WILL CONTINUE TO SHOWCASE
ABOVE NORMAL TEMPERATURES...WITH READINGS ON SATURDAY EXPECTED TO
BE WARMER THAN SUNDAY WHILE THOSE STRONG SOUTHERLY BREEZES DRAW
WARMER AIR INTO THE CWA BEFORE THE COLD FRONTAL PASSAGE SATURDAY
NIGHT.
.LONG TERM...MONDAY THROUGH FRIDAY NIGHT
MAIN FORECAST CONCERN CONTINUES TO BE THE IMPENDING STORM MOVING
INTO THE PLAINS AROUND TUESDAY. THERE IS LITTLE CONSENSUS ON
TIMING. EC HAS SLOWED DOWN EVEN MORE...BRINGING THE MAIN BRUNT OF
THE SYSTEM INTO THE STATE TUE NIGHT/WED. GFS IS STILL THE
FASTER...MORE NORTHERLY (BUT SLIGHTLY MORE SOUTHERLY THAN PREVIOUS
RUNS) OUTLIER. CANADIAN IS TRYING TO STRIKE A BALANCE BUT COULD
EASILY BE A COUPLE OF HUNDRED MILES (OR MORE) OFF OF FINAL
SOLUTION. THEREFORE HAVE LEANED TOWARD HPC SOLUTION FOR NOW.
WITH THAT IN MIND...KEPT POPS LIMITED TO LESS THAN 40 (LESS THAN
30 WHERE IT PLAYED WELL WITH OTHERS). PRECIP SHOULD BEGIN AS RAIN
THEN GRADUALLY CHANGE TO SNOW AS THE SYSTEM PROGRESSES EAST.
OVERNIGHT LOWS ON MON WILL LEND THEMSELVES TO AT LEAST A RAIN/SNOW
MIX IF NOT ALL SNOW. AFTER FROPA ALL MODELS ARE INDICATING COLD
ENOUGH AIR TO SUPPORT ALL SNOW. HEAVIEST PRECIP SHOULD BE EAST OF
THE JAMES RIVER VALLEY. A SECONDARY SHORTWAVE MAY DROP DOWN TUE NIGHT/WED
AFTER THE MAIN SYSTEM EXITS EAST BRINGING SOME ADDITIONAL SNOW
SHOWERS OUT WEST.
&&
.AVIATION...
GOOD VFR IS IN PLACE ACROSS THE REGION TONIGHT. THROUGH TOMORROW
EVENING VFR CONDITIONS WILL PREVAIL ALTHOUGH BLUSTERY WINDS WILL
ARRIVE TOMORROW MORNING.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...KEEFE
SHORT TERM...DORN
LONG TERM...WISE
AVIATION...KEEFE
WEATHER.GOV/ABERDEEN
000
FXUS63 KUNR 202140
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
240 PM MST FRI NOV 20 2009
.DISCUSSION...21Z SFC ANALYSIS SHOWS LEE SIDE TROUGH EXTENDING
FROM A LOW PRESSURE CENTER OVER ALBERTA INTO EASTERN WYOMING AND
EASTERN COLORADO. UPPER ANALYSIS SHOWS RIDGING OVER THE NORTHERN
PLAINS WITH A TROUGH MOVING ONTO THE WEST COAST.
THE PRESSURE GRADIENT WILL TIGHTEN TONIGHT AS THE SFC TROUGH
MOVES SLOWLY EAST INTO WESTERN SOUTH DAKOTA. GUSTY SOUTHWESTERLY
WINDS WILL DEVELOP WEST OF THE TROUGH AXIS OVER NORTHEASTERN
WYOMING THIS EVENING. PRESSURE GRADIENT ANALYSIS ALSO SHOWS THE
POTENTIAL FOR GUSTY SOUTHWESTERLY DOWNSLOPE WINDS TO DEVELOP OVER
THE NORTHERN BLACK HILLS AND THE ADJACENT FOOTHILLS TONIGHT.
FORECAST WINDS ALOFT SHOW THAT GUSTS AS HIGH AS 50 MPH WILL BE
POSSIBLE IN THOSES AREAS OVERNIGHT SO HAVE ISSUED A WIND ADVISORY
FOR THE NORTHERN AND NORTHEASTERN FOOTHILLS OF THE BLACK HILLS
TONIGHT.
ON SATURDAY...THE UPPER TROUGH APPROACHES FROM THE WEST...PUSHING
A COLD FRONT INTO NORTHEASTERN WYOMING AND NORTHWESTERN SOUTH
DAKOTA BY MIDDAY...THEN CROSSING THE REST OF THE AREA SATURDAY
AFTERNOON AND EVENING. THE FRONT WILL USHER IN COOLER AIR WITH
LIMITED MOISTURE. WILL CONTINUE LOW POPS IN THE WEST NEAREST BEST
FORCING.
ON SUNDAY...THE SURFACE HIGH SHIFTS EAST WITH RETURN FLOW IN THE
WEST. NEXT SHORTWAVE SWINGS INTO THE REGION FOR LOW POPS SUNDAY
NIGHT. HIGH TEMPERATURES WILL BE NOTICEABLY COLDER SUNDAY...A RETURN
TO MORE SEASONAL CONDITIONS.
EXTENDED...GFS ENSEMBLE MEMBERS SHOWING GOOD AGREEMENT ON SWINGING
TROUGH THROUGH THE CWA ON MONDAY. ECMWF AND GEM OPERATIONAL RUNS
ALSO CONSISTENT WITH THESE SOLUTIONS. THE ECMWF AND GEM RUNS DIVERGE
FROM GFS GOING INTO MONDAY NIGHT...WRAPPING UP AN UPPER LOW ALONG
THE NEBRASKA AND KANSAS BORDER. RMOP INDICATING LOWER PREDICTABILITY
WITH THIS SYSTEM. WILL KEEP CHANCE POPS ACROSS SOUTH CENTRAL
PORTIONS OF THE CWA ATTM MONDAY INTO TUESDAY. HAVE BUMPED TEMPS DOWN
ACROSS THE CWA UNDER COOL NORTHWEST FLOW.
THE GFS SHOWS ANOTHER WAVE SWEEPING ACROSS THE CWA TUESDAY NIGHT
INTO WEDNESDAY. NEITHER GEM NOR ECMWF AGREE WITH THIS SCENARIO.
SEVERAL GFS ENSEMBLE MEMBERS POINTING TO THIS SOLUTION...SO WILL
KEEP SLIGHT CHANCE POPS ACROSS THE CWA FOR THIS TIMEFRAME. MODELS
CONSISTENT WITH BUILDING RIDGE ACROSS THE WESTERN CONUS THURSDAY
INTO FRIDAY AHEAD OF NEXT TROUGH. ATTM IT APPEARS THAT THE CWA WILL
BE DRY GOING INTO LATE NEXT WEEK.
&&
.AVIATION...SOUTHWEST WINDS OF 20 TO 30 KTS WITH GUSTS TO 40 KTS
WILL DEVELOP ACROSS NORTHEAST WYOMING...THE NORTHERN BLACK
HILLS...AND NORTHERN FOOTHILLS TONIGHT. THE WINDS WILL SUBSIDE
SATURDAY MORNING. VFR CONDITIONS CAN BE EXPECTED THROUGH THE
FORECAST PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVISORY FROM 9 PM THIS EVENING TO 6 AM MST SATURDAY FOR
NORTHERN FOOT HILLS-STURGIS/PIEDMONT FOOT HILLS.
WY...NONE.
&&
$$
GR/JW
000
FXUS63 KFSD 202122
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
322 PM CST FRI NOV 20 2009
.DISCUSSION...
QUIET NIGHT ACROSS THE AREA AS WINDS GRADUALLY SWING AROUND TO THE
SOUTH AND SOUTHEAST AND INCREASE...ESPECIALLY OVER THE WEST. WENT
WITH NON DIURNAL TEMPERATURES ALONG AND WEST OF THE JAMES RIVER AS
WINDS BEGIN TO INCREASE MORE STEADILY. EVEN HAVE TEMPERATURES RISING
A LITTLE TOWARDS 12Z IN THE FAR EAST. OTHERWISE...DECREASED LOWS A
LITTLE FROM ABOUT INTERSTATE 29 EAST WITH LIGHT FLOW AND CLEAR SKIES
THROUGH MUCH OF THE NIGHT. LOWS SHOULD RANGE FROM THE MID TO UPPER
20S EAST OF INTERSTATE 29 TO THE LOWER 30S WEST OF THE JAMES RIVER.
SATURDAY SHOULD PROVE TO BE A MILD BUT BREEZY DAY AS WINDS INCREASE
TO SOMETHING AROUND 20 TO 30 MPH ON A STRONG SOUTHERLY GRADIENT.
MOISTURE ALSO SET TO INCREASE ALONG INCOMING LLJ SO HAVE PARTLY TO
MOSTLY CLOUDY SKIES IN THE EAST DURING THE AFTERNOON. QUIET A BIT OF
MOISTURE RETURN JUST OFF THE SFC AND THIS LOOKS REASONABLE GIVEN
HIGHER DEW POINT AIR IN EASTERN OKLAHOMA. HIGHS MAINLY IN THE 50S.
SATURDAY NIGHT WILL SEE A WIND SHIFT WORK INTO THE AREA AHEAD OF AN
ENTRANCE REGION TO A RELATIVELY WEAK UPPER LEVEL JET STREAK. MAY BE
JUST ENOUGH LIFT ALOFT AND JUST ENOUGH MOISTURE CONVERGENCE IN THE
LOW TO MID LEVELS TO SUPPORT A LITTLE LIGHT RAIN OVER THE EASTERN
CWA...BUT WILL HOLD OFF ON BETTER CHANCES UNTIL SUNDAY. EXPECT
CLOUDS TO ALSO INCREASE DURING THIS TIME AS THE UPPER WAVE
APPROACHES THE DECENT LOW TO MID LEVEL MOISTURE. LOWS WILL BE
MILD...ESPECIALLY IN THE EAST WHERE THE STRONGER SOUTHERLY FLOW
REMAINS IN PLACE...AND SHOULD RANGE FROM THE LOWER 40S IN NW IA TO
30 TO 35 IN CENTRAL SD.
AS STATED EARLIER...WILL MAINTAIN SOME LOWER END POPS IN THE EAST
FOR A FEW RAIN SHOWERS WITH INCOMING WEAK ENTRANCE REGION AND WEAK
MID TO LOW LEVEL MOISTURE CONVERGENCE. THIS SHOULD KEEP CLOUD COVER
IN PLACE MUCH OF THE DAY...BUT DECREASE SLOWLY FROM WEST TO EAST. A
LITTLE COOLER BUT A LOT LESS WIND SO STILL MILD...WITH HIGHS FROM
THE UPPER 40S TO LOWER 50S. /08
HEADING INTO SUNDAY NIGHT...AFTER SOME HINT OF A DYNAMIC DOWNTIME
AFTER WAVE SHEARS BY TO THE NORTHEAST...THE TRAILING SYSTEM STARTS
TO INCREASE LOW LVL FLOW AGAIN WITH ISENTROPIC TRANPORT INCREASING
THRU THE CWA FROM S TO N. A LITTLE LOWER TO MID LVL CONVERGENCE
AXIS LOOKS TO SET UP FROM SW TO NE ACRS THE AREA LIFTING SLOWLY
NE...AND ENOUGH TO PERHAPS FOCUS A SMALL POP LATER IN THE NIGHT.
THE INCREASING SELY FLOW...CLOUDS...AND MOISTURE LKLY TO KEEP TMPS
WARM ENOUGH AT TIME OF PCPN THREAT FOR ALL RAIN...BUT ANY QUICKER
APPROACH WOULD PERHAPS BRING SOME LIGHT FREEZING RAIN TO THE MIX.
MONDAY GETS SOME BETTER DIV Q IN THE MIX ADVANCING OUT AHEAD OF THE
TROUGH DIGGING INTO THE CNTRL/SRN PLAINS. MAIN MID LVL
BNDRY/CONVERGENCE STARTS TO LOCK INTO THE NRN/SWRN CWA...AND WOULD
SEEM TO BE A SLIGHTLY BETTER FOCUS FOR MID TO HIGH CHC POPS. START
TO LIMIT DIURNAL RANGE SOMEWHAT MORE WITH HIGH AMT OF CLDS.
FOR THE EXTENDED RANGE /MON NIGHT THRU FRI/ ALMOST FUNNY HOW CHANGES
IN THE LONG RANGE GUIDANCE...ESPECIALLY AFFECTING THE START OF THE
PERIOD...WAS PREDICTABLE. FOR THE MOST PART THE VARIOUS CAMPS HAVE
NOT ABANDONED THEIR RESPECTIVE SLNS...WITH GFS CONTINUING AS THE
PROGRESSIVE POSTER CHILD...BUT THE CANADIAN/ECMWF/UKMET ALL ON THE
SLOW AND DIGGY SIDE...WITH 12Z RUNS OF THE FORMER PAIR EVEN MORESO.
ENCOURAGING WAS GFS HALF STEP BACK TOWARD MORE DIGGING. THEREFORE...
HARD TO DENY THAT THERE WILL NOT BE A PRECIPITATION EVENT IN THE
MONDAY NIGHT TO TUESDAY NIGHT WINDOW /ALTHOUGH LATEST GUIDANCE
TRENDS WOULD PERHAPS PUSH BACK A PERIOD OR SO FOR BEST FORCING/.
INTRODUCED SOME LKLY POPS THRU THE NWRN HALF OF THE CWA FOR THE
MOMENT...TAPERING OFF SLIGHTLY TOWARD THE FAR SE. WRAPPED UP LOWS
NOTORIOUS FOR SLOW PROGRESSION AND LOOKS TO BE ONE WHERE AN EVENTUAL
TROWAL STRUCTURE IS PROBABLE...ALONG WITH A HEALTHY INVERTED
TROUGH...FAVORING PCPN ALG/BEHIND. THESE TYPES OF SYSTEM ALSO SEEM
TO HAVE A TENDENCY TO BRING UP WARMER AND MOIST AIR...WRAPPING WELL
WESTWARD FOR A WHILE. CERTAINLY THE BETTER OF THE SNOW THREAT WOULD
BE BACK ALG/W OF THE INVERTED TROUGH...AND DO NOT HAVE SUGGESTIONS
OF A DRIER ELY TRAJECTORY TO HELP WET BULB THINGS. THEREFORE...KEPT
ANY SNOW MENTION LIMITED TO THE EXTREME WEST...WITH MIX TOWARD THE
JAMES VALLEY MONDAY NIGHT...THEN ON A BIT EASTWARD TUE...BEFORE
STARTING A WHOLE SCALE CHANGEOVER TUE NIGHT. SOME LINGERING POPS
CONTINUED THRU THE NE/E ON WEDNESDAY.
THE END OF THE WEEK IS FEATURED DRY AT THIS POINT AS RIDGING
REBOUNDS THRU THE NRN PLAINS. SFC RIDGE MOVING OVER THU INTO EARLY
FRI COULD LEAD TO SOME CHILLY LOWS...ESPLY IF WRN AREAS HAVE ANY
DECENT SNOWCOVER. SOME COLD AIR SC MAY BE AROUND ON THU THRU ERN
CWA...BUT MAINLY CLEAR TO MO CLR EXPECTED BY THU NIGHT/FRI. FOR
NOW...DID NOT FULLY ACCEPT THE RAPIDITY OF THE WARMUP ON FRIDAY...
BUT WL BE SOMETHING TO WATCH FOR ONCE THE EVOLUTION OF THE EARLY TO
MID WEEK SYSTEM IS DEFINED. /CHAPMAN
&&
.AVIATION...
PRETTY MUCH VFR THROUGH 0Z SUNDAY. NOT OUT OF THE QUESTION TO SEE
SOME VALLEY FOG LATE TONIGHT...BUT COVERAGE SHOULD BE MINIMAL. WE
WILL SEE AN INFLUX OF MOISTURE ON SATURDAY AFTERNOON...WITH THE
POTENTIAL FOR HIGH END MVFR CEILINGS AT SUX...AND POSSIBLY FSD.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KABR 202007
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
207 PM CST FRI NOV 20 2009
.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT
FORECAST CHALLENGES CONTINUE TO BE WIND SPEEDS ON SATURDAY AND
TEMPERATURES THROUGHOUT THE SHORT TERM.
CURRENTLY...HIGH PRESSURE AT THE SURFACE AND ALOFT OVER THIS CWA
IS CLAIMING RESPONSIBILITY FOR THE SUNNY SKY AND LIGHT WINDS.
TEMPERATURES ARE WORKING INTO THE UPPER 40S WITH A FEW LOCATIONS
ALREADY NUDGING UP INTO THE LOW 50S.
RETURN FLOW SETS UP ACROSS THE CWA TONIGHT AND PERSISTS RIGHT ON
THROUGH SATURDAY. SURFACE TO 925HPA WIND SPEEDS CONTINUE IN THE 15
TO 30 KNOT RANGE...SO BREEZY TO WINDY SOUTH WINDS STILL ON COURSE.
THE FIRST IN A SERIES OF LOW PRESSURE SYSTEMS WORKS THROUGH THE
FORECAST AREA SATURDAY AND SATURDAY NIGHT...DRAGGING A COLD FRONT
THROUGH THE CWA. THIS FIRST LOW WILL NOT HAVE ENOUGH MOISTURE TO
WORK WITH TO PRODUCE MEASURABLE PRECIPITATION. HOWEVER...RETURN
FLOW MOISTURE WORKING INTO THE REGION...MAY BE JUST ENOUGH TO
SUPPORT LOW STRATUS CLOUD FORMATION ACROSS THE FAR EASTERN
FORECAST AREA /KATY AND K8D3 AND KETH AND KVVV/ SATURDAY NIGHT
INTO SUNDAY. A SECOND AREA OF LOW PRESSURE /THE ONE BEING WATCHED
CLOSELY/ STARTS TO ENCROACH UPON THE CWA AND THE SHORT RANGE
FORECAST BY SUNDAY NIGHT...WITH SATURATION OF THE ATMOSPHERIC
COLUMN REALLY GETTING GOING SUNDAY NIGHT. FOR NOW...HAVE WORKED TO
COORDINATE APPX THE SWRN HALF OF THE CWA IN RATHER LOW-END POPS
SUNDAY NIGHT. FOLLOWING THE WINT WX TYPES PROCEDURE TO DETERMINE
P-TYPE...SUNDAY NIGHT TURNS OUT TO BE A POSSIBLE MIX OF RAIN/FRZNG
RAIN AND/OR SNOW...ESPECIALLY ACROSS THE SOUTHEASTERN FORECAST
ZONES.
TEMPERATURES THROUGHOUT THE SHORT TERM WILL CONTINUE TO SHOWCASE
ABOVE NORMAL TEMPERATURES...WITH READINGS ON SATURDAY EXPECTED TO
BE WARMER THAN SUNDAY WHILE THOSE STRONG SOUTHERLY BREEZES DRAW
WARMER AIR INTO THE CWA BEFORE THE COLD FRONTAL PASSAGE SATURDAY
NIGHT.
.LONG TERM...MONDAY THROUGH FRIDAY NIGHT
MAIN FORECAST CONCERN CONTINUES TO BE THE IMPENDING STORM MOVING
INTO THE PLAINS AROUND TUESDAY. THERE IS LITTLE CONSENSUS ON
TIMING. EC HAS SLOWED DOWN EVEN MORE...BRINGING THE MAIN BRUNT OF
THE SYSTEM INTO THE STATE TUE NIGHT/WED. GFS IS STILL THE
FASTER...MORE NORTHERLY (BUT SLIGHTLY MORE SOUTHERLY THAN PREVIOUS
RUNS) OUTLIER. CANADIAN IS TRYING TO STRIKE A BALANCE BUT COULD
EASILY BE A COUPLE OF HUNDRED MILES (OR MORE) OFF OF FINAL
SOLUTION. THEREFORE HAVE LEANED TOWARD HPC SOLUTION FOR NOW.
WITH THAT IN MIND...KEPT POPS LIMITED TO LESS THAN 40 (LESS THAN
30 WHERE IT PLAYED WELL WITH OTHERS). PRECIP SHOULD BEGIN AS RAIN
THEN GRADUALLY CHANGE TO SNOW AS THE SYSTEM PROGRESSES EAST.
OVERNIGHT LOWS ON MON WILL LEND THEMSELVES TO AT LEAST A RAIN/SNOW
MIX IF NOT ALL SNOW. AFTER FROPA ALL MODELS ARE INDICATING COLD
ENOUGH AIR TO SUPPORT ALL SNOW. HEAVIEST PRECIP SHOULD BE EAST OF
THE JAMES RIVER VALLEY. A SECONDARY SHORTWAVE MAY DROP DOWN TUE NIGHT/WED
AFTER THE MAIN SYSTEM EXITS EAST BRINGING SOME ADDITIONAL SNOW
SHOWERS OUT WEST.
&&
.AVIATION...
FOR THE MOST PART...VFR CONDITIONS WILL BE PRESENT AT ALL TAF
SITES THROUGH THE NEXT 24 HOURS. WINDS WILL BE INCREASING OUT OF
THE SOUTH TO 15 TO 30 KT BY TOMORROW MORNING ACROSS THE CWA.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
SHORT TERM...DORN
LONG TERM...WISE
AVIATION...WISE
WEATHER.GOV/ABERDEEN
000
FXUS63 KFSD 201659
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1059 AM CST FRI NOV 20 2009
.DISCUSSION...
QUIET AND MILD DAY ACROSS THE AREA WITH A WEAK WEST TO NORTHWEST
FLOW EXPECTED. A WEAK SFC RIDGE PASSES TODAY...WHICH SHOULD BEND THE
WINDS BACK AROUND TO A LIGHT SOUTH OR SOUTHWEST AROUND SUNSET.
OTHERWISE...HIGHS MAINLY IN THE LOWER TO MID 50S LOOKS ON TRACK.
&&
.AVIATION...
PRETTY MUCH VFR THROUGH 18Z SATURDAY. WE WILL SEE AN INFLU OF
MOISTURE ON SATURDAY AFTERNOON...WITH THE POTENTIAL FOR HIGH END
MVFR CEILINGS AT SUX...AND POSSIBLY FSD. NOT OUT OF THE QUESTION TO
SEE SOME VALLEY FOG LATE TONIGHT...BUT COVERAGE SHOULD BE MINIMAL.
&&
.PREV DISCUSSION...
WEAK SFC TROF ALONG I29 DRIFTING TO THE E. DRIER AIR BEHIND THIS FNT
WITH DPS DROPPING INTO THE UPPER TEENS WITH FAIRLY MOIST AIR TO THE
E OF TROF. FOG IS ALSO FORMING E OF TROF AND WL MENTION AREAS OF
DENSE FOG E OF I29 THRU 15Z. OTHERWISE AFTER FOG BURNS OFF E...SHUD
BE MOSUNNY ACRS ALL OF CWA WITH SOME PASSING THIN CI. SHUD BE
ANOTHER MILD DAY WITH HIGHS IN THE LOWER TO MID 50S.
TEMPS SHUD DROP OFF QUICKLY THIS EVE AND THEN HOLD STEADY OR SLOWLY
RISE AFTER 06Z AS LOW LEVEL SELY FLOW INCREASES AHEAD OF NEXT
APPROACHING FNT. SAT SHUD BE A FEW DEG WARMER...BUT SLY WINDS SHUD
GUST TO 30 TO 35 MPH WITH INCREASING LLJ. THIS LLJ SHUD BRING UP
INCREASING LLM SAT NITE AND WUD EXPECT FAIRLY WDSPRD STRATUS AFTER
06Z ESPEC E OF JAMES VALLEY. WL KEEP MENTION OF SPOTTY RW- LATE SAT
NITE INTO SUN MORN AHEAD OF FNT AND S/W. COULD BE MORE OF A DRIZZLE
EVENT THAN ANYTHING ELSE. S/W SHUD PUSH FNT THRU BY 18Z SUN AND CUD
SEE A DECENT AMOUNT OF SUN SUN AFTERNOON ESPEC W OF I29. THIS SHUD
ALLOW TEMPS TO RISE BACK INTO LOWER 50S ACRS THE W WITH COOLER 40S
WHERE CLOUDS PERSIST LONGEST ACRS THE E.
LOOKS LIKE EC AND GEM BECOMING CLOSER IN AGREEMENT WITH PHASING NRN
STREAM S/W WITH SRN STREAM S/W MON AFTN INTO TUES WITH RAPID
CYCLOGEN ACRS CNTRL PLAINS BY MON EVE. GFS SEEMS NOW TO BE THE
OUTLIER AND EVEN SOMEWHAT OF AN OUTLIER ON SPAGETTI PROGS. GEM/EC
SOLUTION WUD PRODUCE A SIG STORM ESPEC MON NITE INTO TUES WITH POT
FOR SIG RAIN/SNOW ACRS WRN CWA AND RAIN E. HAVE UPPED POPS ACRS CWA
MON INTO TUE FOR THIS REASON AND LATER SHIFTS MAY HAVE TO UP POPS
EVEN SIG MORE IF THIS TREND CONTS. THIS TIME OF YEAR THESE PHASING
SYS CAN RAPIDLY DEVELOP A SIG STORM WITH WDSPRD PRECIP AND VERY
STRONG WINDS. FOR MOST OF THE DAY MON...ANY PRECIP THAT DOES OCCUR
SHUD BE FAIRLY LIGHT BUT STILL CUD RESULT IN HIGH POPS. AGAIN...THE
MAIN ACTION IF GEM/EC ARE CORRECT WUD BE MON NITE INTO TUES. DID
LOWER MAX TEMPS ON TUES WITH COLDER AIR AND POT FOR WDSPRD PRECIP.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KUNR 201655
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
955 AM MST FRI NOV 20 2009
.DISCUSSION...16Z SURFACE ANALYSIS HAD WEAK HIGH EAST OF THE CWA
WITH LEE TROUGH FROM EASTER MT INTO WESTERN SD. UPPER RIDGE OVER THE
ROCKIES SPILLING CI INTO THE NORTHERN PLAINS. WARM AIR ADVECTION
WILL BE FEATURED TODAY WITH HIGHS NEAR GUIDANCE. FORECAST REMAINS ON
TRACK SO NO UPDATES PLANNED ATTM.
GRADIENT TIGHTENS TONIGHT ALONG WITH PRESSURE FALLS...SO WOULD
EXPECT TYPICAL AREAS TO SEE WINDY SPOTS OVERNIGHT IN NORTHEASTERN
WY/THE BLACK HILLS. LOWS WILL STAY UP IN THESE AREAS.
SATURDAY...UPPER TROUGH ZIPS IN FROM THE WEST PUSHING A COLD FRONT
INTO THE CWA BY MIDDAY...AND EXITING SATURDAY EVENING. THE FRONT
WILL BRING COOLER AIR WITH LIMITED MOISTURE. WILL CONTINUE LOW
POPS IN THE WEST NEAREST BEST FORCING.
SUNDAY...SURFACE HIGH SHIFTS EAST WITH RETURN FLOW IN THE WEST.
NEXT SHORTWAVE SWINGS INTO THE REGION FOR LOW POPS SUNDAY NIGHT.
IT WILL BE NOTICEABLY COLDER SUNDAY...A RETURN TO MORE SEASONAL
CONDITIONS.
EXTENDED...MODELS CONTINUE TO HAVE TROUBLE WITH THE EXACT TIMING
AND PLACEMENT WITH SYSTEMS MOVING THROUGH FOR THE BEGINNING INTO
THE MIDDLE OF THE WEEK. AT ANY RATE...PATTERN WILL BE ACTIVE SO
WILL HAVE IN POPS THROUGH MANY OF THE PERIODS.
&&
.AVIATION...VFR CONDITIONS CAN BE EXPECTED THROUGH THE FORECAST
PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
000
FXUS63 KABR 201605 AAA
AFDABR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
1005 AM CST FRI NOV 20 2009
.UPDATE...
NO CHANGES PLANNED TO THE FORECAST AT THIS TIME. TEMPERATURES
SHOULD WARM INTO THE 50S FOR MOST AREAS TODAY. SHIPPED OUT AN
UPDATED SET OF GRIDS/WORDS TO REMOVE MORNING PATCHY FOG WORDING.
&&
.PREV DISCUSSION...
.SHORT TERM...TODAY THROUGH SUNDAY
MODELS HAVE VERY GOOD AGREEMENT THROUGH THE SHORT TERM WITH A
CONTINUATION OF ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS. FOR
THIS MORNING...SURFACE HIGH PRESSURE RIDGE WAS OVER THE EASTERN
DAKOTAS SLIDING EAST. DESPITE HAVING CLEAR SKIES AND LIGHT
WINDS...ATY WAS THE ONLY LOCATION TO HAVE SOME FOG EARLY THIS MORNING.
SURFACE DEWPOINT SPREADS CONTINUE TO BE IN THE 3 TO 4 DEGREE RANGE
ACROSS MUCH OF THE EASTERN CWA. THUS...ANY MORE FOG THAT FORMS
THIS MORNING SHOULD BE GENERALLY LIGHT WITH MAYBE SOME PATCHY
SHALLOW DENSER FOG. THUS...WENT WITH JUST PATCHY FOG EARLY THIS
MORNING FOR THE JAMES VALLEY EAST. OTHERWISE...THE SURFACE HIGH
PRESSURE RIDGE WILL MOVE EAST TONIGHT WITH WINDS BECOMING SOUTH ON
THE BACKSIDE. WITH ONLY SOME CIRRUS COMING OVER THE UPPER RIDGE
MOVING INTO THE REGION FROM THE WEST...SKIES TODAY SHOULD BE
MOSTLY SUNNY WITH WARMER TEMPS THAN YESTERDAY. THE UPPER RIDGE
MOVES EAST ACROSS THE REGION THROUGH TONIGHT AND EARLY SATURDAY
WHILE A STRONG UPPER LEVEL TROUGH MOVES IN FROM THE WEST. AS A
RESULT OF THIS UPPER LEVEL TROUGH...THE SURFACE PRESSURE GRADIENT
WILL TIGHTEN UP ACROSS THE CWA TONIGHT AND SATURDAY WITH A BIG
INCREASE IN LL WINDS. MODELS SHOW SOUTH WINDS OFF THE SURFACE
INCREASING TO 40 TO 50 KNOTS ACROSS THE CWA LATER TONIGHT AND
SATURDAY. THE DEPTH OF THE MIXING LAYER WILL DETERMINE THE
STRENGTH OF THE SURFACE WINDS ON SATURDAY AND THINK IT WILL BE
DEEP ENOUGH FOR IT TO BECOME WINDY ACROSS ALL OF THE CWA. TONIGHTS
LOWS WILL BE FAIRLY MILD FOR THIS TIME OF YEAR AS WINDS INCREASE
FROM THE SOUTH. SATURDAYS HIGHS WILL ALSO BE THE WARMEST ACROSS
THE CWA IN AWHILE WITH GOOD WAA. HIGHS SHOULD BE IN THE 50S TO
AROUND 60 DEGREES SOUTHWEST IN THE CWA.
THE UPPER LEVEL TROUGH SWINGING ACROSS THE REGION SATURDAY AND
SATURDAY NIGHT WILL ALSO PUSH A COLD FRONT THROUGH AT THE SURFACE.
DESPITE HAVING DEEP LAYER UVV IN ADVANCE OF THIS TROUGH...VERY DRY
AIR WILL ONLY RESULT IN MID AND HIGH LEVEL CLOUDS DEVELOPING. WITH
LOW LEVEL MOISTURE INCREASING ON THE SOUTH WINDS...EXPECT SOME LOW
CLOUDS TO DEVELOP ALONG I-29 AND EAST SATURDAY NIGHT AND INTO
SUNDAY MORNING. THE WINDS WILL SHIFT TO THE WEST AND NORTHWEST
BEHIND THE FRONT SATURDAY NIGHT AND CONTINUE THROUGH MUCH OF
SUNDAY ACROSS THE CWA. TSCTS AND SOUNDINGS SHOW THAT SUNDAY WILL
HAVE MORE CLOUD COVER ACROSS THE CWA MAINLY IN THE MID AND UPPER
LEVELS. SUNDAY WILL ALSO BE ABOUT 10 DEGREES COOLER. WINDS SHOULD
TURN AROUND TO THE SOUTHEAST OUT WEST SUNDAY AFTERNOON AS WE START
TO GET THE INFLUENCE FROM THE NEXT UPPER LEVEL TROUGH.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
ALL EYES ARE ON THE STORM SYSTEM PULLING OUT INTO THE
CENTRAL/NORTHERN PLAINS EARLY NEXT WEEK. THERE CONTINUE TO BE
DIFFERENCES IN STRENGTH AND PATH OF THE STORM...BUT THE EC AND
CANADIAN ARE IN DECENT AGREEMENT NOW...WITH THE GFS SEEN AS AN
OUTLIER. STILL MANY ISSUES TO IRON OUT WITH THIS STORM.
EC/CANADIAN BRING A SHARP SHORTWAVE EASTWARD OUT OF THE ROCKIES
AND INTO THE PLAINS ON MONDAY...QUICKLY BECOMING A CLOSED LOW AT
500MB. SFC LOW TRACKS EAST/NORTHEAST THROUGH IOWA SPREADING PRECIP
NORTHWARD ACROSS A GOOD PORTION OF THE CWA MONDAY NIGHT INTO
TUESDAY. GFS ON THE OTHER HAND SHOWS A WEAKER AND MORE PROGRESSIVE
WAVE TRACKING MUCH FARTHER NORTH. THE GFS ALSO HAS MORE COLDER AIR
ASSOCIATED WITH THIS SYSTEM COMPARED TO THE EC/CANADIAN SOLUTIONS.
THE LATTER SOLUTIONS WOULD SUGGEST PERHAPS MOSTLY A RAIN EVENT
ACROSS THE EASTERN CWA UNTIL TOWARDS THE END OF THE EVENT...AT
LEAST FOR THE EASTERN CWA. AGAIN...MANY ISSUES TO IRON OUT YET
BUT IF THE EC/CANADIAN SOLUTION VERIFIES AND ENOUGH COLD AIR WORKS
INTO THIS SYSTEM...COULD BE LOOKING AT A DECENT SNOW MAKER EARLY
NEXT WEEK...WILL BE KEEPING A CLOSE EYE ON THIS. HAVE INCREASED
POPS TO 40S ACROSS A GOOD PORTION OF THE CWA AND MAY NEED TO GO
HIGHER. AFTER THIS SYSTEM MOVES THROUGH THE AREA MODELS ARE
HINTING AT A REINFORCING SHOT OF COLDER AIR DROPPING SOUTHEAST
OVER THE AREA WITH ANOTHER FAST MOVING SHORTWAVE.
&&
.AVIATION...
FOR THE MOST PART...VFR CONDITIONS WILL BE PRESENT AT ALL TAF
SITES THROUGH THE NEXT 24 HOURS. ONLY EXCEPTION WILL BE KATY WHICH
WILL EXPERIENCE BR THROUGH THE MORNING HOURS.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...DORN
SHORT TERM...MOHR
LONG TERM...TMT
AVIATION...WISE
WEATHER.GOV/ABERDEEN
000
FXUS63 KUNR 200946
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
246 AM MST FRI NOV 20 2009
.DISCUSSION...09Z SURFACE ANALYSIS HAD WEAK HIGH EAST OF THE CWA
WITH LEE TROUGH FROM CENTRAL MT INTO EASTERN WY. UPPER RIDGE OVER
THE ROCKIES SPILLING CI INTO THE NORTHERN PLAINS. WARM AIR
ADVECTION WILL BE FEATURED TODAY WITH HIGHS NEAR GUIDANCE.
GRADIENT TIGHTENS TONIGHT ALONG WITH PRESSURE FALLS...SO WOULD
EXPECT TYPICAL AREAS TO SEE WINDY SPOTS OVERNIGHT IN NORTHEASTERN
WY/THE BLACK HILLS. LOWS WILL STAY UP IN THESE AREAS.
SATURDAY...UPPER TROUGH ZIPS IN FROM THE WEST PUSHING A COLD FRONT
INTO THE CWA BY MIDDAY...AND EXITING SATURDAY EVENING. THE FRONT
WILL BRING COOLER AIR WITH LIMITED MOISTURE. WILL CONTINUE LOW
POPS IN THE WEST NEAREST BEST FORCING.
SUNDAY...SURFACE HIGH SHIFTS EAST WITH RETURN FLOW IN THE WEST.
NEXT SHORTWAVE SWINGS INTO THE REGION FOR LOW POPS SUNDAY NIGHT.
IT WILL BE NOTICEABLY COLDER SUNDAY...A RETURN TO MORE SEASONAL
CONDITIONS.
EXTENDED...MODELS CONTINUE TO HAVE TROUBLE WITH THE EXACT TIMING
AND PLACEMENT WITH SYSTEMS MOVING THROUGH FOR THE BEGINNING INTO
THE MIDDLE OF THE WEEK. AT ANY RATE...PATTERN WILL BE ACTIVE SO
WILL HAVE IN POPS THROUGH MANY OF THE PERIODS.
&&
.AVIATION...VFR CONDITIONS CAN BE EXPECTED THROUGH THE FORECAST
PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
HELGESON/SCHILD
000
FXUS63 KABR 200935
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
335 AM CST FRI NOV 20 2009
.SHORT TERM...TODAY THROUGH SUNDAY
MODELS HAVE VERY GOOD AGREEMENT THROUGH THE SHORT TERM WITH A
CONTINUATION OF ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS. FOR
THIS MORNING...SURFACE HIGH PRESSURE RIDGE WAS OVER THE EASTERN
DAKOTAS SLIDING EAST. DESPITE HAVING CLEAR SKIES AND LIGHT
WINDS...ATY WAS THE ONLY LOCATION TO HAVE SOME FOG EARLY THIS MORNING.
SURFACE DEWPOINT SPREADS CONTINUE TO BE IN THE 3 TO 4 DEGREE RANGE
ACROSS MUCH OF THE EASTERN CWA. THUS...ANY MORE FOG THAT FORMS
THIS MORNING SHOULD BE GENERALLY LIGHT WITH MAYBE SOME PATCHY
SHALLOW DENSER FOG. THUS...WENT WITH JUST PATCHY FOG EARLY THIS
MORNING FOR THE JAMES VALLEY EAST. OTHERWISE...THE SURFACE HIGH
PRESSURE RIDGE WILL MOVE EAST TONIGHT WITH WINDS BECOMING SOUTH ON
THE BACKSIDE. WITH ONLY SOME CIRRUS COMING OVER THE UPPER RIDGE
MOVING INTO THE REGION FROM THE WEST...SKIES TODAY SHOULD BE
MOSTLY SUNNY WITH WARMER TEMPS THAN YESTERDAY. THE UPPER RIDGE
MOVES EAST ACROSS THE REGION THROUGH TONIGHT AND EARLY SATURDAY
WHILE A STRONG UPPER LEVEL TROUGH MOVES IN FROM THE WEST. AS A
RESULT OF THIS UPPER LEVEL TROUGH...THE SURFACE PRESSURE GRADIENT
WILL TIGHTEN UP ACROSS THE CWA TONIGHT AND SATURDAY WITH A BIG
INCREASE IN LL WINDS. MODELS SHOW SOUTH WINDS OFF THE SURFACE
INCREASING TO 40 TO 50 KNOTS ACROSS THE CWA LATER TONIGHT AND
SATURDAY. THE DEPTH OF THE MIXING LAYER WILL DETERMINE THE
STRENGTH OF THE SURFACE WINDS ON SATURDAY AND THINK IT WILL BE
DEEP ENOUGH FOR IT TO BECOME WINDY ACROSS ALL OF THE CWA. TONIGHTS
LOWS WILL BE FAIRLY MILD FOR THIS TIME OF YEAR AS WINDS INCREASE
FROM THE SOUTH. SATURDAYS HIGHS WILL ALSO BE THE WARMEST ACROSS
THE CWA IN AWHILE WITH GOOD WAA. HIGHS SHOULD BE IN THE 50S TO
AROUND 60 DEGREES SOUTHWEST IN THE CWA.
THE UPPER LEVEL TROUGH SWINGING ACROSS THE REGION SATURDAY AND
SATURDAY NIGHT WILL ALSO PUSH A COLD FRONT THROUGH AT THE SURFACE.
DESPITE HAVING DEEP LAYER UVV IN ADVANCE OF THIS TROUGH...VERY DRY
AIR WILL ONLY RESULT IN MID AND HIGH LEVEL CLOUDS DEVELOPING. WITH
LOW LEVEL MOISTURE INCREASING ON THE SOUTH WINDS...EXPECT SOME LOW
CLOUDS TO DEVELOP ALONG I-29 AND EAST SATURDAY NIGHT AND INTO
SUNDAY MORNING. THE WINDS WILL SHIFT TO THE WEST AND NORTHWEST
BEHIND THE FRONT SATURDAY NIGHT AND CONTINUE THROUGH MUCH OF
SUNDAY ACROSS THE CWA. TSCTS AND SOUNDINGS SHOW THAT SUNDAY WILL
HAVE MORE CLOUD COVER ACROSS THE CWA MAINLY IN THE MID AND UPPER
LEVELS. SUNDAY WILL ALSO BE ABOUT 10 DEGREES COOLER. WINDS SHOULD
TURN AROUND TO THE SOUTHEAST OUT WEST SUNDAY AFTERNOON AS WE START
TO GET THE INFLUENCE FROM THE NEXT UPPER LEVEL TROUGH.
.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY
ALL EYES ARE ON THE STORM SYSTEM PULLING OUT INTO THE
CENTRAL/NORTHERN PLAINS EARLY NEXT WEEK. THERE CONTINUES TO BE
DIFFERENCES IN STRENGTH AND PATH OF THE STORM...BUT THE EC AND
CANADIAN ARE IN DECENT AGREEMENT NOW...WITH THE GFS SEEN AS AN
OUTLIER. STILL MANY ISSUES TO IRON OUT WITH THIS STORM.
EC/CANADIAN BRING A SHARP SHORTWAVE EASTWARD OUT OF THE ROCKIES
AND INTO THE PLAINS ON MONDAY...QUICKLY BECOMING A CLOSED LOW AT
500MB. SFC LOW TRACKS EAST/NORTHEAST THROUGH IOWA SPREADING PRECIP
NORTHWARD ACROSS A GOOD PORTION OF THE CWA MONDAY NIGHT INTO
TUESDAY. GFS ON THE OTHER HAND SHOWS A WEAKER AND MORE PROGRESSIVE
WAVE TRACKING MUCH FARTHER NORTH. THE GFS ALSO HAS MORE COLDER AIR
ASSOCIATED WITH THIS SYSTEM COMPARED TO THE EC/CANADIAN SOLUTIONS.
THE LATTER SOLUTIONS WOULD SUGGEST PERHAPS MOSTLY A RAIN EVENT
ACROSS THE EASTERN CWA UNTIL TOWARDS THE END OF THE EVENT...AT
LEAST FOR THE EASTERN CWA. AGAIN...MANY ISSUES TO IRON OUT YET
BUT IF THE EC/CANADIAN SOLUTION VERIFIES AND ENOUGH COLD AIR WORKS
INTO THIS SYSTEM...COULD BE LOOKING AT A DECENT SNOW MAKER EARLY
NEXT WEEK...WILL BE KEEPING A CLOSE EYE ON THIS. HAVE INCREASED
POPS TO 40S ACROSS A GOOD PORTION OF THE CWA AND MAY NEED TO GO
HIGHER. AFTER THIS SYSTEM MOVES THROUGH THE AREA MODELS ARE
HINTING AT A REINFORCING SHOT OF COLDER AIR DROPPING SOUTHEAST
OVER THE AREA WITH ANOTHER FAST MOVING SHORTWAVE.
&&
.AVIATION...
FOR THE MOST PART...VFR CONDITIONS WILL BE PRESENT AT ALL TAF
SITES THROUGH THE NEXT 24 HOURS. ONLY EXCEPTION WILL BE KATY WHICH
WILL EXPERIENCE BR/FG THROUGH THE MORNING HOURS. VSBYS WILL DROP
TO BELOW 1SM AT TIMES.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
SHORT TERM...MOHR
LONG TERM...TMT
AVIATION...TMT
WEATHER.GOV/ABERDEEN
000
FXUS63 KFSD 200908
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
310 AM CST FRI NOV 20 2009
.DISCUSSION...
WEAK SFC TROF ALONG I29 DRIFTING TO THE E. DRIER AIR BEHIND THIS FNT
WITH DPS DROPPING INTO THE UPPER TEENS WITH FAIRLY MOIST AIR TO THE
E OF TROF. FOG IS ALSO FORMING E OF TROF AND WL MENTION AREAS OF
DENSE FOG E OF I29 THRU 15Z. OTHERWISE AFTER FOG BURNS OFF E...SHUD
BE MOSUNNY ACRS ALL OF CWA WITH SOME PASSING THIN CI. SHUD BE
ANOTHER MILD DAY WITH HIGHS IN THE LOWER TO MID 50S.
TEMPS SHUD DROP OFF QUICKLY THIS EVE AND THEN HOLD STEADY OR SLOWLY
RISE AFTER 06Z AS LOW LEVEL SELY FLOW INCREASES AHEAD OF NEXT
APPROACHING FNT. SAT SHUD BE A FEW DEG WARMER...BUT SLY WINDS SHUD
GUST TO 30 TO 35 MPH WITH INCREASING LLJ. THIS LLJ SHUD BRING UP
INCREASING LLM SAT NITE AND WUD EXPECT FAIRLY WDSPRD STRATUS AFTER
06Z ESPEC E OF JAMES VALLEY. WL KEEP MENTION OF SPOTTY RW- LATE SAT
NITE INTO SUN MORN AHEAD OF FNT AND S/W. COULD BE MORE OF A DRIZZLE
EVENT THAN ANYTHING ELSE. S/W SHUD PUSH FNT THRU BY 18Z SUN AND CUD
SEE A DECENT AMOUNT OF SUN SUN AFTERNOON ESPEC W OF I29. THIS SHUD
ALLOW TEMPS TO RISE BACK INTO LOWER 50S ACRS THE W WITH COOLER 40S
WHERE CLOUDS PERSIST LONGEST ACRS THE E.
LOOKS LIKE EC AND GEM BECOMING CLOSER IN AGREEMENT WITH PHASING NRN
STREAM S/W WITH SRN STREAM S/W MON AFTN INTO TUES WITH RAPID
CYCLOGEN ACRS CNTRL PLAINS BY MON EVE. GFS SEEMS NOW TO BE THE
OUTLIER AND EVEN SOMEWHAT OF AN OUTLIER ON SPAGETTI PROGS. GEM/EC
SOLUTION WUD PRODUCE A SIG STORM ESPEC MON NITE INTO TUES WITH POT
FOR SIG RAIN/SNOW ACRS WRN CWA AND RAIN E. HAVE UPPED POPS ACRS CWA
MON INTO TUE FOR THIS REASON AND LATER SHIFTS MAY HAVE TO UP POPS
EVEN SIG MORE IF THIS TREND CONTS. THIS TIME OF YEAR THESE PHASING
SYS CAN RAPIDLY DEVELOP A SIG STORM WITH WDSPRD PRECIP AND VERY
STRONG WINDS. FOR MOST OF THE DAY MON...ANY PRECIP THAT DOES OCCUR
SHUD BE FAIRLY LIGHT BUT STILL CUD RESULT IN HIGH POPS. AGAIN...THE
MAIN ACTION IF GEM/EC ARE CORRECT WUD BE MON NITE INTO TUES. DID
LOWER MAX TEMPS ON TUES WITH COLDER AIR AND POT FOR WDSPRD PRECIP.
&&
.AVIATION...
WEAK AREA OF HIGH PRESSURE WILL MOVE ACROSS THE REGION TODAY
RESULTING IN LIGHT WINDS AND MOSTLY CLEAR SKIES WITH THE EXCEPTION
OF LOCATIONS SHROUDED IN FOG. AREAS OF FOG WILL PERSIST THROUGH AT
LEAST 15Z EAST OF INTERSTATE 29 ACROSS PORTIONS OF SOUTHWEST
MINNESOTA AND NORTHWEST IOWA AHEAD OF A WEAK TROUGH SHIFTING THROUGH
THE REGION. THE FOG SHOULD GRADUALLY DISSIPATE ACROSS THESE
LOCATIONS...THOUGH MAY LINGER THROUGH THE MID DAY HOURS ACROSS
SOUTHWEST MINNESOTA WITH RELATIVELY DENSE FOG AND LITTLE IN THE WAY
OF LOW LEVEL WINDS. /BT
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KUNR 200416
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
915 PM MST THU NOV 19 2009
.DISCUSSION...AT 03Z WK UPPER TROF AND S/W NOW MVG ACRS CENTRAL
SD. ANOTHER S/W AND WK UPPER TROF MOVING ACRS NRN MONTANA. A
FEW CLOUDS ASSCD WITH THIS S/W WILL MOVE ACRS NWRN SD OVER NEXT
COUPLE OF HOURS. OTHERWISE...SKIES WILL REMAIN MOSTLY CLEAR.
TEMPS MAY GO DOWN A FEW MORE DEGREES...BUT LGT WEST WINDS WL
HELP HOLD TEMPS UP SOME.
CURRENT FCST LOOKS GOOD AND WILL NOT MAKE ANY UPDATES.
PREVIOUS FORECAST DISCUSSION:(240 PM MST)...
ON FRIDAY...AN UPPER RIDGE WILL MOVE OVER THE NORTHERN PLAINS WITH
WARM AIR ADVECTION. THE ATMOSPHERE REMAINS DRY...SO THERE WILL BE
LITTLE IN THE WAY OF CLOUDS. GRADIENT/PRESSURE FALLS FRIDAY NIGHT
WILL SUPPORT WINDY SPOTS OVER NORTHEASTERN WY AND PORTIONS OF THE
BLACK HILLS. LOWS FRIDAY NIGHT WILL BE HELD UP BY WINDS.
ON SATURDAY...THE UPPER RIDGE WILL SHIFT EAST OF THE CWA WITH
UPPER TROUGH MOVING IN AND INCREASING CLOUDS FROM THE WEST. THIS
WILL BRING A COLD FRONT THROUGH THE CWA WITH SMALL CHANCES FOR
PRECIPITATION...ALTHOUGH MOISTURE WILL AGAIN BE LIMITED.
EXTENDED...A CHANGE TO A COOLER AND MORE UNSETTLED WX PATTERN
WILL DEVELOP LATE IN THE WEEKEND AND CONTINUE THROUGH AT LEAST
THE MIDDLE PART OF NEXT WEEK. FAST WEST-NORTHWEST FLOW WILL BRING
A SERIES OF UPPER LEVEL DISTURBANCES ACROSS THE AREA. COOLER
TEMPERATURES CAN BE EXPECTED FOR THE EXTENDED...ALONG WITH WINDY
CONDITIONS AND CHANCES FOR RAIN AND SNOW SHOWERS AS EACH OF THESE
S/W,S PASS THRU. MEDIUM RANGE MODELS ARE HAVING A VERY DIFFICULT
TIME WITH TIMING OF WAVES...SO WILL KEEP CHANCES LOW AND FAIRLY
BROADBRUSHED AT THIS POINT. AT THIS TIME...THE BETTER CHANCES FOR
PCPN LOOK TO BE LATER SUNDAY NIGHT AND MONDAY...THEN AGAIN LATER
TUESDAY AND TUESDAY NIGHT. THANKSGIVING EVE AND ESP THANKSGIVING
DAY LOOK DRY WITH SEASONABLE TEMPS RIGHT NOW...BUT THIS WILL
ULTIMATELY DEPEND ON THE TIMING OF THESE WAVES.
&&
.AVIATION...VFR CONDITIONS CAN BE EXPECTED THROUGH THE FORECAST
PERIOD.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&
$$
000
FXUS63 KFSD 200322
AFDFSD
AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
922 PM CST THU NOV 19 2009
.DISCUSSION...
ONLY FORECAST CONCERN TONIGHT IS FOG. VISIBILITIES ARE DROPPING IN
AREAS EAST OF INTERSTATE 29. ATTM...MOST PLACES ARE 3 TO 5 SM BUT
LIGHT WINDS AND THIN MOISTURE LAYER IS FAVORABLE FOR FURTHER
REDUCTION IN VISIBILITIES TONIGHT. CAN NOT RULE OUT DENSE FOG LATER
TONIGHT...MAINLY INTO NW IA WHERE WINDS ARE GENERALLY CALM.
HOWEVER...CURRENTLY THINKING THE WEAK TROUGH SLIDING THAT IS SLIDING
ACROSS THE AREA...AS NOTICEABLE ON IR SATELLITE...WILL STIR UP THE
ATMOSPHERE JUST ENOUGH TO INHIBIT WIDESPREAD DENSE FOG. MAY EVEN SEE
VISIBILITIES COME UP SOME SHOULD WEAK WRLY FLOW BEHIND THE TROUGH
BEGIN TO MIX WITH THE VERY SHALLOW MOISTURE LAYER. AT ANY
RATE...WILL KEEP AN EYE ON VISIBILITIES TONIGHT. 97
&&
.AVIATION...
PUNCH OF DRY WRLY AIR HAS ERODED MVFR CLOUD DECK THIS EVENING.
LINGERING LOW LEVEL MOISTURE EAST OF MAINLY ALONG AND EAST OF
INTERSTATE 29 REMAINS...SO FOG IS STILL A GOOD POSSIBILITY IN THESE
AREAS TONIGHT. GENERALLY EXPECTING MVFR TYPE VSBYS...BUT CAN NOT
RULE OUT A PERIOD OF IFR TONIGHT. TO THE WEST...SOME PATCHY FOG IS
POSSIBLE...BUT GENERALLY IS NOT EXPECTED TO BE AN AVIATION CONCERN.
FOG WILL QUICKLY BURN OFF AFTER SUNRISE FRI MORNING. 97
&&
.PREV DISCUSSION...
A SAGGY GRADIENT WILL MOVE THROUGH THE CWA TONIGHT WITH WINDS SLOWLY
TRANSITIONING FROM A LIGHTER SOUTHERLY FLOW TO WESTERLY. THIS WILL
BRING A CHANCE FOR FOG JUST AHEAD OF THIS LOW LEVEL
TRANSITION...ALTHOUGH THE LOW LEVEL CONVERGENCE WILL LIKELY BE
WEAKER THAN LAST NIGHT. EITHER WAY...EXPECT SOME FOG TO FORM FROM
ABOUT THE JAMES VALLEY EAST. AS FOR TEMPERATURES...GOING COOLEST IN
THE WEST WHERE SKIES WILL BE MOSTLY CLEAR WITH THE MORE MILD
READINGS UNDER THE LAST BITS OF STRATO CU THAT WILL BE EXITING. /08
FOG WL MOST LKLY BE AROUND AND CONTINUE INTO MID MORNING WITHIN WK
FLOW ENVIROMENT SURROUNDING THE GRADUALLY DISSIPATING WIND SHIFT.
BEST THREAT TO GET A STRONGER WLY PUSH WL BE THRU ELEVATED SW MN
AND INTO SERN SD...BUT EVEN THIS WL WKN AND REVERSE TOWARD SLY BY
EVENING. WL SEE QUITE A BIT OF SUNSHINE AND AGAIN WL DRIVE TMPS
UPWARD TO THE UPPER 40S AND 50S...DESPITE THE WK FLOW. MAY SEE
REPEAT OF SOME FOG FRI NIGHT THRU MAINLY SERN 1/3 OF CWA AS UNMIXED
LOW LVL MOISTURE CONTINUES TO LINGER...AND HAVE WKR GRADIENT.
HOWEVER...THE APPROACH OF THE NEXT TROUGH THRU THE ROCKIES WL START
TO DEVELOP LEE TROUGHING FRI NIGHT...AND THIS WL INCREASE THE SLY
GRADIENT...RESULTING IN SLIGHTLY NON-DIRUNAL TEMPS EAST...AND VERY
MUCH SO IN THE WEST...STEADY TO SLOWLY RISING AFT MIDNIGHT.
OTHER THAN BEING A BREEZY TO WINDY DAY ON SATURDAY...WL HAVE YET
ANOTHER MILD LATE NOVEMBER DAY...WITH WARMEST CONDITIONS AIDED BY
DOWNSLOPE OFF HIER ELEVATIONS THRU SW MN...AND ALSO HIER AREAS W OF
THE JAMES VLY. ONE POTENTIALLY NEGATIVE FACTOR WL BE THE INCREASING
LOW LVL MOISTURE...WHICH TIME SECTIONS INDICATE SHUD BE DEEP ENOUGH
TO RESULT IN SOME PARTIALLY MIXED OUT LOWER CLOUDINESS...OR AT LEAST
A DENT TO THE WARMING.
THE MOISTURE CONTINUES TO BUILD NORTHWARD ON SAT NIGHT...AHEAD OF
BNDRY WHICH LEADING UPR IMPULSE ROTATING NEWRD THRU THE NRN PLAINS.
FORCING IS ACTUALLY FAIRLY DECENT FROM A DIV Q PERSPECTIVE. WHILE
WIND PROFILES ACTUALLY START TO LOOK A LOT MORE DRIZZLY FROM ARND
I29 EASTWARD LTR SAT NIGHT...ALSO WL GET SOME DEEPER TROPSPHERIC
LIFT FORCING...BUT FAIRLY SPARSE MOISTURE ABV. 700-500 HPA LAPSE
RATES ARE PARTICULARLY HORRIBLE...SO LKLY THAT ONLY SHALLOW
PROCESSES WL BE IN PLAY. THE PRECIP POTENTIAL FORCED BY DEEPER
ASCENT DOES IMPROVE BY SUNDAY AS THE WHOLE SYSTEM PROGRESSES
EWRD...AND INCREASED TO 30 POPS SHIFTING EWRD OF MOST OF THE CWA
BY AFTN.
FOR THE EXTENDED RANGE /SUN NIGHT THRU THU/ MODELS CONTINUE TO
STRUGGLE WITH EVOLUTION OF EARLY TO MID WEEK SYSTEM...WHICH WOULD
SEEM TO FAVOR A SUPERENSEMBLE APPROACH. GFS CONTINUED TO FEATURE
THE ZIPPIEST PROGRESSION OF TROUGH...WITH A STRONG SECONDARY TROUGH
FALLING IN TUE/TUE NIGHT...WITH THE ONLY HINTS IN THE ENSEMBLE PLOTS
THE MAX STANDARD DEVIATIONS SUGGESTING A DEEPER AND SLOWER SLN MAY
BE FAVORED...WITH MORE SLIGHTLY MORE NRN/SRN STREAM SPLITTING.
OPERATIONAL 00Z CANADIAN OUTLIER TOWARD THE SLOW SIDE OF ITS
RELATIVE ENSEMBLE...NOT TO MENTION ALMOST ALL SLNS...BUT 12Z HAS
SHIFTED DECISIVELY EWRD TOWARD ECMWF CLUSTERING...WHILE MAINTAINING
ITS MORE DIGGY STATUS. THIS SLN WOULD BE THE MOST THREATENING OF
ALL...RESULTING IN A 24-36H PRECIP EVENT MON THRU TUE...LKLY WITH
SOME SIGNIFICANT SNOWFALL. ECMWF /SHIFTED TOWARD ITS ENS MEAN/ WOULD
SEEM TO OCCUPY A MORE VIABLE SLN SPACE AND HAS BEEN USED FOR
GUIDANCE.
SUN NIGHT MAY START QUIET IN WAKE OF THE FROPA SUNDAY BETWEEN
EXITING WAVE. WITH APPROACHING OF UPSTREAM WRN PLAINS TROUGH...
INCREASING LOW TO MID LVL WAA AND INCREASE IN DIV Q SHUD WL BRING
SLIGHT INCREASE IN THREAT FOR PCPN...AND THERMAL PROFILES WHILE
SUGGEST MAINLY RAIN...WL CARRY SMALL THREAT FOR MIX WITH SNOW VIA
WET BULB IN THE FAR W/NW. ONE PERIOD OF ENHANCED PCPN THREAT SHUD
BE WITH PV FORCING/DIV Q SHUD BE MONDAY. ALL OPERATIONAL MDLS
INDICATE PCPN THREAT TUE /ALBEIT FROM GREATLY DIFFERING SLNS/ AND
SEEMED THAT ALSO A PERIOD TO KEEP A SOMEWHAT HIER POP. SLOWER AND
DEEPER CLUSTER OF SLNS AROUND OPERATIONAL 12Z CANADIAN AND ECMWF
SUGGEST A SIGNIFICANT PRECIP EVENT FOR MON NIGHT INTO TUE. ADDED IN
POPS FOR A START...AND KEPT ALL IN FORM OF SNOWFALL WITH EXCEPTION
OF THE FAR EASTERN AREAS WHERE A CALCULATED MIX WAS MAINTAINED.
PLENTY OF OPPORTUNITY FOR COLDER AIR TO EVOLVE IN ANY SHAPE OF
SYSTEM. AFTER TUE...KEPT THINGS DRY.
FOR THE MOST PART...LATTER PART OF THE EXTENDED HEDGED TMPS TOWARD
LOWER END OF GUIDANCE AS WL CERTAINLY BE A MUCH COOLER AIRMASS THAN
OF RECENT...AND EVEN IF A BIT MORE WIND/CLOUDS/LOW LVL MOISTURE ARE
PRESENT...ENOUGH ROOM TO DROP DOWN A FEW MORE DEGREES...ESPLY IF A
SNOWFALL MAY INTERVENE. /CHAPMAN
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
$$
000
FXUS63 KABR 200042
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
642 PM CST THU NOV 19 2009
.UPDATE...
UPDATE THIS EVENING IS CENTERED ON FOG POTENTIAL FOR FRIDAY
MORNING. THE DEGREE OF UNCERTAINTY REMAINS RATHER HIGH AS
REGION...WHILE NOT UNDER UNFAVORABLE CONDITIONS...IS NOT UNDER
IDEAL CONDITIONS EITHER. MAIN FEATURE...THE SURFACE TROUGH...HAS
ESSENTIALLY WASHED OUT AND MIGRATED TO THE EAST SIDE OF THE COTEAU.
THIS HAS ALLOWED MOST SITES IN THE CWA TO SEE WINDS SHIFT TO
WESTERLY. THE ONLY CAVEAT IS THAT WITHIN THE JAMES VALLEY...THE
BOUNDARY LAYER HAD COMPLETELY DECOUPLED. MEANWHILE EAST OF THE
COTEAU...PATCHY FOG HAS ALREADY BEGUN TO DEVELOP OUTSIDE OF AREAS
EFFECTED BY THE PRE EXISTING STRATUS/ALTOSTRATUS DECK. JUST TO
COMPLICATE MATTERS...HIGH CLOUDS ASSOCIATED WITH THE UPPER TROUGH
MOVING OVER THE JAMES VALLEY AND WILL CONTINUE EAST OVERNIGHT.
THIS FEATURE IS FORECAST BY GFS/NAM TO EXIT OUT OF THE CWA BY
06-09Z. GIVEN THAT THERE WILL BE PLENTY OF TIME FOR IDEAL
RADIATIONAL COOLING AND ADDITIONAL DECOUPLING OF SURFACE BOUNDARY
LAYER...WILL KEEP FORECAST FOR FOG GOING INTO THE LATE MORNING.
THERE WERE NO ADDITIONAL CHANGES TO THE AFTERNOON PACKAGE.
&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
FORECAST CHALLENGES INCLUDE TEMPERATURES THROUGHOUT THE SHORT
RANGE...ALONG WITH WIND SPEEDS ON SATURDAY.
CURRENTLY...A SLOW-MOVING WEAK COLD FRONT...APPX HALFWAY THROUGH
THE FORECAST AREA...IS WORKING EAST. THE FOG AND LOW CLOUDS HAVE
LIFTED/DISSIPATED...AND TEMPERATURES ARE ON THERE WAY INTO THE 40S
TO LOWER 50S.
WITH THE WEAK SURFACE TROF LOOSING ITS IDENTITY WITH EVERY PASSING
HOUR...AND SURFACE HIGH PRESSURE PROGGED TO BUILD INTO THE
FORECAST AREA TONIGHT...SURFACE WINDS BENEATH A CLEAR SKY ARE
EXPECTED TO FALL TO NEXT TO NOTHING OVERNIGHT. THIS IS FAST
BECOMING A POTENTIAL FOG SITUATION...IN PARTICULAR...ACROSS THE
JAMES RIVER VALLEY AGAIN TONIGHT AND LOCATIONS EAST OF THE JAMES
RIVER VALLEY. HAVE TOSSED IN AREAS OF FOG/PATCHY DENSE FOR
PORTIONS OF THE TONIGHT PERIOD...SPILLING OVER INTO THE FRIDAY
MORNING PERIOD. HIGH PRESSURE WILL BE STICKING AROUND THROUGH
FRIDAY AFTERNOON...BEFORE SHIFTING FURTHER EAST...AND SETTING UP
A DECENT PERIOD OF RETURN FLOW SOUTHERLY WINDS FRIDAY NIGHT
THROUGH THE DAY SATURDAY. SURFACE TO 925HPA WINDS SHOW UP BETWEEN
15 AND 30 KNOTS...SO SHOULD BE LOOKING AT A RATHER BREEZY/WINDY
DAY ON SATURDAY. THEN...ANOTHER COLD FRONT STARTS TO TREK THROUGH
THE CWA SATURDAY AFTERNOON/NIGHT...TURNING WINDS AROUND TO THE
WEST-NORTHWEST. THERE IS AN AREA OF LOW PRESSURE FORECAST TO WORK
THROUGH THE MID AND UPPER ATMOSPHERE OVER THIS CWA SATURDAY AND
SATURDAY NIGHT. HOWEVER...WITH PRETTY MUCH ALL THE MOISTURE
AVAILABLE FOR THIS LOW TO WORK WITH BOTTLED UP IN THE MID AND
UPPER PORTIONS OF THE ATMOSPHERE...THE SYSTEM IS EXPECTED TO ONLY
GENERATE SOME MID/HIGH CLOUD COVER...AND WORK THROUGH THE REGION
WITHOUT PRODUCING ANY PRECIPITATION.
TEMPERATURES WILL CONTINUE ON THEIR CURRENT PACE OF RUNNING A GOOD
10 TO 15 DEGREES ABOVE NORMAL...IN THE 40S AND 50S FRIDAY AND
SATURDAY.
.LONG TERM...SUNDAY THROUGH THURSDAY NIGHT
A SHORTWAVE MOVING THROUGH THE REGION ON SUNDAY SHOULD HAVE LITTLE
IMPACT IN TERMS OF PRECIP. HOWEVER WINDS WILL BE GUSTY AHEAD OF
THE WAVE AND TEMPS WILL BE A LITTLE COOLER BEHIND IT. WITH THE
COOLER TEMPS AND ADDITIONAL LIFT THERE IS A SLIGHT CHANCE FOR SOME
RW/SW TO ROLL OFF THE HILLS AND MOVE INTO THE SOUTHERN COUNTIES
SUNDAY NIGHT.
ALL BETS ARE OFF FROM MONDAY ONWARD. MODELS HAVE BEEN FLAKY
REGARDING TIMING AND SOUTHERN EXTENT OF SHORTWAVES MOVING OUT OF
THE NORTHERN PACIFIC. ENSEMBLES HAVE HANDLED IT BEST...SO HAVE
TRENDED TOWARD HPC SOLUTION FOR THE EXTENDED. GFS CONTINUES TO BE
A LITTLE TOO FAST AND EC IS A LITTLE TOO FAR SOUTH ON THE TROF
EXTENSION. WITH THAT IN MIND THERE IS A LITTLE MORE OR LESS PRECIP
IN THE GRIDS AND A LITTLE SLOWER PROGRESSION THAN THE OPERATIONAL
RUNS MAY SUGGEST THROUGH WEDNESDAY. KEPT POPS 20 OR LESS AS THIS
IS A VERY LOW CONFIDENCE FORECAST REGARDING TIMING.
&&
.AVIATION...
WESTERLY WINDS THIS EVENING WILL GO LIGHT/VARIABLE OVERNIGHT...AND
GRADUALLY SHIFT AROUND TO THE SOUTH LATE IN THE MORNING. FOG
DEVELOPMENT A DISTINCT POSSIBILITY DURING THE MORNING HOURS FOR
KABR/KATY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...CONNELLY
SHORT TERM...DORN
LONG TERM...WISE
AVIATION...CONNELLY
WEATHER.GOV/ABERDEEN
| 
