FXUS63 KABR 231533 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
933 AM CST WED DEC 23 2009

.UPDATE...
EXPANDED AREAS OF FREEZING DRIZZLE TO THE MO RIVER THROUGH NOON
BASED ON MORNING REPORTS AND SOUNDINGS. THERE IS A WELL SATURATED
LAYER BELOW THE SNOW GROWTH THAT SHOULD KEEP THINGS GOING RIGHT
UNTIL THE MAIN BRUNT OF THE SYSTEM MOVES IN. FOR EXTREME EASTERN
SD THE FZDZ WILL LAST INTO THIS EVENING AND THE GRIDS HAVE BEEN
UPDATED TO REFLECT THAT. HOWEVER WITH NO ICE ACCUMULATION BEING
REPORTED WILL STICK WITH AREAS OF FZDZ AND A NOW CAST RATHER THAN
MUDDYING THE WATERS WITH A SECOND LESSER HEADLINE LEADING INTO THE
WSW THIS EVENING. NEW AVIATION DISCUSSION BELOW.

&&
.PREV DISCUSSION...
.SHORT TERM...TODAY THROUGH FRIDAY MORNING
FORECAST CHALLENGES REMAIN TIMING AND INTENSITY OF THE APPROACHING
WINTER STORM SYSTEM.

CURRENTLY RADAR IMAGERY IS SHOWING INCREASING RETURNS IN THE
WESTERN PART OF THE STATE...HOWEVER NO SNOW HAS BEEN OBSERVED.  I
DID TREND BACK THE START AND EASTERN EXTENT OF THE SNOWFALL IN
THE GRIDS FOR THIS MORNING AND AFTERNOON. THE AREA IS COVERED BY
IFR CIGS AND IFR/MVFR VSBYS. BESIDES FOG...REPORTS OF FZDL WERE
RECEIVED FROM KPIR AND LIGHT MIST REPORTS FROM KATY. THEREFORE
ADDED MENTION OF AREAS OF FZDL ALONG SOUTHERN AND EASTERN COUNTIES
THROUGH 15Z THIS MORNING.

THE WINTER STORM WARNING IS STILL IN EFFECT AND MODELS AGREE ON
THE GENERAL DEVELOPMENT OF THE WINTER STORM SYSTEM. THE NEW RUNS
OF THE GFS STILL CLOSE OFF THE SURFACE LOW SOMEWHAT QUICKER
RESULTING IN A LOW TRACK SLIGHTLY SOUTH AND WEST THAN THAT OF THE
ECMWF. THE NEW RUN OF THE ECMWF IS ALSO CONSISTENT IN SHOWING A
STRONGER UPPER WAVE DROPPING OUT OF THE NORTHWEST THURSDAY
MORNING. THIS WAVE THEN MERGES WITH THE MAIN UPPER LOW.

THE FORECAST IS STILL ON TRACK WITH WIDESPREAD SNOWFALL BEGINNING
WEDNESDAY AND INCREASING BY THURSDAY MORNING AND INTO FRIDAY.
MODELS STILL INDICATE THE BEST LARGE SCALE FORCING AND WAA FRIDAY
MORNING. THE GFS SHOWS UP TO 15 MICROBARS OF OMEGA IN THE SNOW
GROWTH ZONE FROM 6Z TO 12Z ON FRIDAY. 

ALSO BUMPED UP WIND SPEEDS/GUSTS IN THE GRIDS AS MODELS SHOW A
VERY TIGHT PRESSURE GRADIENT ON THE BACK SIDE OF THIS SYSTEM.
WINDS START TO INCREASE FROM WEST TO EAST THURSDAY. BY FRIDAY
MORNING WHEN LARGE SCALE FORCING IS AT ITS PEAK...WIND GUSTS UP TO
40 MPH ARE POSSIBLE. THIS COULD PUT MOST OF THE CWA IN BLIZZARD
CONDITIONS AND THE WINTER STORM WARNING MAY HAVE TO BE UPGRADED TO
A BLIZZARD WARNING AT SOME POINT DURING THIS PERIOD.

.LONG TERM...FRIDAY THROUGH TUESDAY
THE MODELS AND GFS ENSEMBLES SHOW EXCELLENT AGREEMENT WITH THE
LARGE UPPER LEVEL AND SURFACE LOW PRESSURE AREA FROM FRIDAY
THROUGH SUNDAY. ON FRIDAY...THE MODELS SHOW THE SURFACE LOW
PRESSURE AREA IN WESTERN IOWA BOTTOMING OUT AS IT SLOWLY WOBBLES
EAST ACROSS THE STATE THROUGH FRIDAY NIGHT AND WEAKENS. THE
SURFACE LOW PRESSURE AREA CONTINUES TO WEAKEN AS IT LIFTS
NORTHEAST INTO THE GREAT LAKES REGION THROUGH SUNDAY MORNING.
INCREASED POPS ACROSS THE BOARD FOR FRIDAY AND FRIDAY NIGHT AS THE
MODELS CONTINUE TO SHOW QUITE A BIT OF QPF WRAPPING AROUND INTO
OUR AREA. ALSO...EXTENDED POP CHANCES INTO SATURDAY AND SATURDAY
NIGHT ACROSS THE EASTERN CWA. WITH THE CONTINUATION OF SNOWFALL
ALONG WITH STRONG NORTH WINDS...WILL EXTEND THE WINTER STORM
WARNING THROUGH 12Z SATURDAY ACROSS THE CWA. OTHERWISE...THE SNOW
WILL END AND THE CLOUDS AND WINDS WILL DECREASE SATURDAY NIGHT AND
SUNDAY AS SURFACE HIGH PRESSURE BUILDS IN. WITH THIS SURFACE HIGH
PRESSURE AREA AND ADDITIONAL SNOW COVER...IT WILL CONTINUE TO BE COLD
WITH BELOW NORMAL TEMPERATURES THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK.

&&

.AVIATION...
IFR CEILINGS ARE EXPECTED THROUGH TODAY AND TONIGHT WITH 1 TO 5SM
IN FOG THROUGH THE DAY. THERE WILL BE SOME LIGHT FREEZING DRIZZLE
AT ALL TAF SITES THROUGH LATE MORNING. KATY MAY EVEN SEE LIGHT
FREEZING DRIZZLE CONTINUING THROUGH MID AFTERNOON. OTHERWISE...LIGHT
SNOW IS EXPECTED TO DEVELOP LATER THIS AFTERNOON AND EARLY EVENING
FROM SOUTH TO NORTH AFFECTING ALL OF THE TAF LOCATIONS. THE SNOW
WILL INCREASE IN INTENSITY THROUGH TONIGHT WITH VISIBILITIES
FALLING TO BELOW 1/2SM AT TIMES.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WARNING FROM 6 PM CST /5 PM MST/ THIS EVENING TO 6 
     AM CST /5 AM MST/ SATURDAY FOR BROWN-BUFFALO-CAMPBELL-CLARK-
     CODINGTON-CORSON-DAY-DEUEL-DEWEY-EDMUNDS-FAULK-GRANT-HAMLIN-
     HAND-HUGHES-HYDE-JONES-LYMAN-MARSHALL-MCPHERSON-POTTER-
     ROBERTS-SPINK-STANLEY-SULLY-WALWORTH.

MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM CST SATURDAY 
     FOR BIG STONE-TRAVERSE.

&&

$$
UPDATE...WISE
SHORT TERM...KRAMLICH
LONG TERM...MOHR
AVIATION...SD

WEATHER.GOV/ABERDEEN