FXUS63 KABR 260211
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
811 PM CST WED NOV 25 2009

.UPDATE...
CLOUDS OVER MUCH OF THE CWA THIS EVENING WILL CONTINUE TO
DISSIPATE THROUGH THE NIGHT AS SINKING MOTION AND DRIER AIR TAKES
OVER. UPDATED FORECAST TO REFLECT THE DECREASING CLOUD TREND.
WINDS WILL ALSO BE FALLING OFF THROUGH THE NIGHT. 

&&
.PREV DISCUSSION...
.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
FORECAST CHALLENGE IS TEMPERATURE.

CURRENTLY...THE PRESSURE GRADIENT OVER THE AREA TODAY...WHICH HAS
BEEN AIDING IN THE BREEZY TO WINDY CONDITIONS...IS RELAXING AS
HIGH PRESSURE TO THE WEST BUILDS INTO THE FORECAST AREA. THERE IS
PLENTY OF BKN/OVC COVERAGE OF LOW CLOUDS STILL AROUND...SOME OF IT
FORMED FROM DAYTIME HEATING/MIXING...AND SOME OF IT REMAINING FROM
THE CAA LOW STRATUS CLOUD DECK THAT WORKED IN EARLIER THIS MORNING.

TONIGHT...AS THIS AREA OF HIGH PRESSURE AT THE SURFACE BUILDS EAST
ACROSS THE DAKOTAS...SURFACE WINDS WILL RELAX TO A LIGHT AND
VARIABLE STATE WHILE THE LOW CLOUDS GRADUALLY DISAPPEAR/SHIFT
EAST. SHOULD SEE ALL OR MOST OF THE LOW CLOUDINESS GONE FROM THIS
AREA BY LATE TONIGHT. WITH WINDS REALLY DYING OFF AND CLOUDS
EXPECTED TO WANE AS THE NIGHT PROGRESSES...TEMPERATURES SHOULD
STEADY OUT LATE TONIGHT MAINLY IN THE TEENS ABOVE ZERO.

STABLE HIGH PRESSURE ESTABLISHES DOMINANCE OVER THE FORECAST AREA
ON THURSDAY AND FRIDAY...WITH A LOW LEVEL WAA SEQUENCE BEGINNING
ON THURSDAY AND CONTINUING INTO FRIDAY THAT SHOULD PUSH
TEMPERATURES BACK UP TO BEING A GOOD 10 OR MORE DEGREES ABOVE
NORMAL HEADING INTO THE WEEKEND. THE BIGGEST CHALLENGE IS
DETERMINING JUST HOW FAR EAST THE LOW LEVEL WAA WILL GET ON
THURSDAY. THE WESTERN THIRD OF FORECAST ZONES WILL LIKELY BE
WORKING TOWARD 50 DEGREES ON THURSDAY. HOWEVER...FURTHER
EAST...TEMPERATURES MAY ONLY REBOUND INTO THE LOWER 40S IN LESS OF
A MIXING BOUNDARY LAYER WIND AND WEAKER LOW LEVEL WAA.

.LONG TERM...SATURDAY THROUGH WEDNESDAY 

MEDIUM RANGE MODELS CONTINUE IN PRETTY GOOD AGREEMENT ALTHOUGH
THERE IS SOME SIGNIFICANT DIFFERENCE IN LATER TIME PERIODS. THE
PERIOD OPENS WITH A DIGGING UPPER LEVEL WESTERN TROUGH IN SYNC
WITH A PROGRESSIVE UPPER LEVEL TROUGH MOVING ACROSS SOUTHERN
CANADA. THIS NORTHERN TROUGH EVENTUALLY BECOMES ABSORBED BY THE
POLAR VORTEX BUT REMAINS IN PHASE WITH THE SOUTHERN UNITED STATES
ENERGY THROUGH MOST OF THIS PERIOD. DURING THE DAY SUNDAY AS THE
SOUTHWEST UPPER LEVEL LOW DRIFTS SOUTHWEST THE NORTHERN TROUGH
BECOMES MORE DEVELOPED AND DRIFTS ACROSS THIS AREA ON SUNDAY. HAVE
CUT BACK THE TIME DURATION A LITTLE FROM THE GOING GRIDS BUT DID
LEAVE IT ACROSS THE ENTIRE AREA SUNDAY. WOULD NOT BE SURPRISED TO
SEE THE AREA CUT A LITTLE TO HIGH LIGHT THE EAST HALF OF THE AREA
IF SUBSEQUENT MODELS ARE CONSISTENT. AFTER THE TROUGH PASSES
SUNDAY AN UPPER LEVEL RIDGE REBUILDS ACROSS THE AREA WITH THE NEXT
WESTERN TROUGH FORMING AND CROSSING THE ROCKIES MONDAY NIGHT INTO
TUESDAY. THIS SYSTEM WILL HAVE A BETTER SURFACE REFLECTION THAT
WILL MOVE THROUGH TUESDAY. THIS SYSTEM WILL HANG UP TUESDAY SO NOT
AFFECT THE EASTERN HALF OF THE STATE BEFORE LATE WEDNESDAY.
MOISTURE WILL BE LIMITED WITH THIS SYSTEM BEING A NORTHERN BRANCH
SYSTEM AND HAVING CROSSED THE ROCKIES. ONE NOTABLE FEATURE WILL
LIKELY BE THE LONG FETCH ON THE BACKSIDE OF THE UPPER LEVEL LOW. A
SOURCE REGION NEAR THE ARCTIC LOOKS LIKE IT WILL NOT LACK COLD
AIR. TODAY THE CANADIAN ARCTIC WAS NOT BITTER COLD BUT STILL COLD
ENOUGH TO DROP TEMPERATURES AROUND HERE TO NORMAL OR A LITTLE BELOW. 

&&

.AVIATION...
MIXING LAYER VFR SCT-OVC 3500-5000 FOOT CLOUDS OVER THE TAF SITES
THIS EVENING WILL SLOWLY BREAKUP INTO THE EARLY MORNING HOURS AS
THEY TREK SOUTHEAST. EXPECT SKIES TO BECOME CLEAR OVER ALL TAF
SITES BY SUNRISE WITH SOME HIGH CIRRUS CLOUDS SPREADING OVER THE
AREA ON THURSDAY. NO SIGNIFICANT WEATHER OR WINDS ARE EXPECTED
THROUGH THURSDAY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

$$
UPDATE...MOHR
SHORT TERM...DORN
LONG TERM...KEEFE
AVIATION...MOHR

WEATHER.GOV/ABERDEEN