FXUS63 KABR 050255
AFDABR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
855 PM CST THU DEC 4 2008
.UPDATE...
TEMPERATURES ARE HOLDING A LITTLE WARMER THAN EXPECTED. CURRENT
SATELLITE LOOPS SHOWS WESTERN EDGE OF LOW CLOUDS MOVING EAST WITH
HOLES DEVELOPING. EXPECT THAT WHEN CLOUDS DISSIPATE TEMPERATURES
WILL DROP QUICKLY WITH JAMESTOWN ND AT 6F LAST HOUR. WATERTOWN IS
REPORTING FLURRIES BUT DO NOT EXPECT THIS TO AMOUNT TO MUCH WITH
NO ACCUMULATION AND OF LIMITED DURATION. DO NOT EXPECT TO UPDATE
CURRENT FORECAST PACKAGE. IT APPEARS TO BE ON TRACK BUT WILL
MONITOR FOR LOW TEMPERATURES DROPPING BELOW ADVERTISED VALUES
AROUND ZERO TO PLUS 5F.
&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH 12Z SUNDAY.
MAIN FCST CHALLENGE IN THE NEAR TERM DEALS WITH TEMPS
TONIGHT...AND SNOW CHANCES FOR FRIDAY NIGHT AND AGAIN SATURDAY
NIGHT.
MSAS SHOWS HIGH PRESSURE SLOWLY SINKING SOUTHWARD OVER THE UPPER
PLAINS..WITH COOL TEMPERATURES IN PLACE. MANY PLACES THIS
AFTERNOON STAYED IN THE MID TEENS...WITH DWPTS RIGHT NOW IN THE
SINGLE DIGITS BETWEEN ZERO AND PLUS 5 F. CONCERN IS THAT SAT PIX
SHOW LARGE FETCH OF CLOUDS UPSTREAM INTO ERN MT/SRN CANADA THAT
CONTS TO DRIFT SOUTHWARD. THIS DECK HAS DEVELOPED STRATO-
CU...LEADING TO THOUGHT THAT IT MAY BE DIFFICULT TO BREAK UP
OVERNIGHT. BUFKIT SOUNDINGS SHOW THAT LOW LEVEL CLOUD DECK SETS UP
ACROSS THE EASTERN PART OF CWA...UNDER DEVELOPING INVERSION.
HOWEVER...CLEARING IS BEGINNING TO TAKE SHAPE ACROSS ERN MT. FWC
GUIDANCE SHOWS KABR FALLING TO -8 F FOR A LOW...WITH KATY FALLING
TO -3 F. HAVE OPTED TO LEAN MORE TOWARD WARMER MAV GUIDANCE...AND
UNDERCUT 3 OR 4 DEGREES. IF SKIES DO INDEED CLEAR OUT AS THE
GUIDANCE SUGGESTS...WITH FRESH SNOW ON THE GROUND...SUB-ZERO
READINGS ARE ENTIRELY POSSIBLE.
NW FLOW ALOFT REMAINS OVER THE REGION THROUGH THE NEAR TERM. A
COUPLE OF THE STRONGER IMPULSES DROP THROUGH THE AREA FRIDAY
NIGHT...AND AGAIN SATURDAY NIGHT.
FOR THE FRIDAY NIGHT SYSTEM...THE GFS SHOWS A FAIRLY ROBUST 7H AND
85H THETA-E RIDGE THAT PASSES THROUGH AHEAD OF THE SYSTEM. THE
FORCING THROUGH THE LOW LAYERS ISN'T ALL THAT IMPRESSIVE..IE...THE
OMEGA FIELDS...BUT 85H-7H SPEC HUMIDITY FIELDS FROM 1 TO 2 G/KG
ACROSS THE EAST. ASSOCIATED SFC LOW DROPS SOUTHEAST THROUGH
MN...WITH BETTER LOW LEVEL FORCING/FRONTOGENESIS TAKING PLACE
ACROSS THE FAR NERN PARTS OF THE CWA. INHERITED WX GRIDS HAD
LIKELY POPS IN PLACE FOR FRIDAY NIGHT...AND SAW NO REASON TO
DEVIATE.
FOR THE NEXT WAVE DROPPING DOWN SATURDAY NIGHT...NUMEROUS DETAILS
NEED TO BE FIGURED OUT. COLD HIGH FOLLOWING FRIDAY NIGHT SYSTEM
SETS UP RESIDENCE OVER THE CWA...WITH THE HIGH PRESSURE AXIS
REACHING MN BY 12Z SUNDAY. SFC TRAJECTORIES WILL COME OFF THE DRY
HIGH TO THE EAST SATURDAY NIGHT...WITH A RAPID MOISTENING TAKING
PLACE THE FURTHER WEST ONE TRAVELS. THE MODELS ACTUALLY SHOW A BIT
HIGHER SPEC HUMIDITIES THROUGH THE LOWER LAYERS FOR SATURDAY
NIGHT...WITH THE HIGHEST VALUES BEING ACROSS WRN SD. AM A BIT
LEERY OF REALLY HITTING POPS HARD SATURDAY NIGHT UNTIL AM ABLE TO
DETERMINE WESTWARD EXTENT OF LOW LEVEL DRY AIR THAT WILL BE
ENTRAINED IN. DID UP POPS INTO THE HIGH CHC CATEGORY THOUGH...AS
FRONTOGENETIC FORCING. GFS BUFKIT CROSS SECTION FOR KPIR SHOWS A
LITTLE BIT OF FORCING MOVING THROUGH SNOW GROWTH REGION...BUT
ISN'T REALLY IMPRESSIVE.
.LONG TERM...SUNDAY THROUGH THURSDAY
LOOKS LIKE WINTER HAS SET IN TO STAY IN THE LONG TERM. GUIDANCE IS
FAIRLY CONSISTENT IN PLACEMENT AND PROGRESSION OF FEATURES THROUGH
A MAJORITY OF THE FORECAST PERIOD...WITH TWO DISTINCT FOCUSES FOR
DISCUSSION. THE FIRST OF THESE IS A SERIES UPPER WAVES THAT CROSS THE
HIGH PLAINS IN THE CLASSIC PROGRESSION OF NORTHWEST FLOW...IE TRAVERSING
ACROSS A WEST COAST RIDGE TOWARDS THE HUDSON LOW. THE FIRST OF
THESE WILL MOVE ACROSS THE CWA SUNDAY...WITH WEAKER SHORTWAVES
FOLLOWING FOR THE START OF THE WORK WEEK AND POSSIBLY MID WEEK.
PROFILES WITH THIS FIRST SYSTEM REMAIN COLD ENOUGH FOR SNOW WITH
THE EXCEPTION OF POSSIBLY THE SOUTHWEST CORNER OF THE CWA.
PREVIOUS FORECASTS HAVE HIGHLIGHTED THIS SAME FEATURE...ALONG AND
EAST OF THE MISSOURI...SO HAVE INCREASED POPS TO HIGH END CHANCE. AS FOR THE
SERIES OF FEATURES ALOFT...WILL SEE THE PERSISTENT BOUNDARY REMAIN
ANCHORED ACROSS THE CWA...WITH LITTLE MOVEMENT...PROVIDING THE
OPPORTUNITY NEXT WEEK TO SEE SEVERAL DAYS OF LIGHT SNOW.
LASTLY...TEMPERATURES THIS PERIOD EXPECTED TO REMAIN VERY WINTERLIKE.
NAEFS TEMPERATURE ANOMALIES AT H85 AND H925 REMAIN AT OR A
STANDARD DEVIATION BELOW CLIMATOLOGY THROUGHOUT THE PERIOD. WILL
KEEP TEMPERATURES AT OR BELOW CLIMATOLOGY DESPITE BRIEF WARM
ADVECTION REGIME LATE SUNDAY...AS FORECAST CONTINUES TO
ADD/MAINTAIN CURRENT SNOW COVER.
&&
.AVIATION...
CEILINGS CONTINUE AROUND 3500 FT AGL ACROSS MUCH OF EASTERN SOUTH
DAKOTA. SATELLITE LOOP SHOWS CLOUDS DISSIPATING FROM THE WEST WITH
THE WESTERN EDGE NOW MOVING OFF THE MO RIVER AND THE ENTIRE BAND
BECOMING SMALLER. SOME HIGH CLOUDS ARE NOTED IN EASTERN MONTANA
MOVING THROUGH THE UPPER LEVEL RIDGE. THESE CLOUDS ARE HIGHER THAN
15K FT. FOR THE REST OF TONIGHT EXPECT VFR CONDITIONS ACROSS THE
AREA WITH CEILINGS AROUND 3500 FT AGL AND UNRESTRICTED VISIBILITY.
AN EXCEPTION WOULD BE THE WATERTOWN AREA WHERE SOME FLURRIES ARE
NOTED ON THE EDGE OF THE CLOUDS. THESE FLURRIES ARE NOT EXPECTED
TO LAST NOR BE HEAVY ENOUGH TO REDUCE VISIBILITY BELOW 6 STATUTE MILES.
LATER THIS EVENING CLOUDS WILL DISSIPATE AND CEILINGS WILL BE
UNLIMITED WITH UNRESTRICTED VISIBILITY.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&
$$
UPDATE...KEEFE
SHORT TERM...HINTZ
LONG TERM...CONNELLY
AVIATION...KEEFE
WEATHER.GOV/ABERDEEN
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