FXUS63 KABR 222128
AFDABR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
328 PM CST TUE DEC 22 2009

.SHORT TERM...TONIGHT AND WEDNESDAY
FORECAST CHALLENGE IS TIMING THE START OF SNOW ON WEDNESDAY.

CURRENTLY...SKIES ARE CLOUDY...WITH TEMPERATURES STEADY OR SLOWLY
RISING INTO THE 20S. THE CWA IS IN A WEAK PRESSURE GRADIENT
BETWEEN HIGH PRESSURE TO THE NORTHEAST AND LOW PRESSURE BEGINNING
TO DEEPEN ALONG THE FRONT RANGE OF THE ROCKIES FROM SOUTHEASTERN
WYOMING ALL THE WAY DOWN THE FRONT RANGE INTO TEXAS. THIS PUTS
WINDS MAINLY OUT OF THE EAST AROUND 10 TO 15 MPH.

LOW CLOUDS WILL STICK AROUND ALL NIGHT AND DURING THE DAY ON
WEDNESDAY. SO...TEMPERATURES...ONCE AGAIN...ARE NOT EXPECTED TO
DROP OFF MUCH OVERNIGHT TONIGHT...OR REBOUND MUCH ON WEDNESDAY.
SHOULD STILL BE SEEING A PREDOMINANTLY EASTERLY SURFACE WIND
THROUGH THE DAY ON WEDNESDAY...BEFORE THE DEEPENING CENTRAL PLAINS
SURFACE LOW STARTS TO SWITCH WINDS AROUND TO THE NORTH. THERE WILL
ALSO BE A SURFACE TROF /COLD FRONT/ WORKING TOWARD THE NORTHWEST
CORNER OF THE FORECAST AREA LATE IN THE DAY ON WEDNESDAY. AN UPPER
LOW WORKING SOUTHEASTWARD OUT OF CANADA...GENERATING THE SURFACE
TROF APPROACHING FROM THE NORTHWEST...WILL ALSO BE GENERATING SOME
LIGHT TO MODERATE SNOWFALL THAT IS EXPECTED TO BE ENCROACHING UPON
THOSE NORTHWESTERN-MOST FORECAST ZONES BY THE END OF THE DAY ON
WEDNESDAY. ADD THAT TO THE AREA OF LOW PRESSURE APPROACHING FROM
THE SOUTH LATE IN THE DAY ON WEDNESDAY AND IT APPEARS AS THOUGH
THE CWA MAY BE SEEING TWO DIFFERENT AREAS OF SNOWFALL CONVERGING
ON THE FORECAST AREA BY LATE IN THE DAY ON WEDNESDAY. CONTINUING
THE TREND OF GRADUALLY INCREASING POPS FROM LATE TONIGHT THROUGH
THE DAY WEDNESDAY FROM WEST TO EAST...WITH SNOW ACCUMULATIONS ON
WEDNESDAY LIMITED TO GENERALLY AN INCH OR LESS.

THERE IS ALSO AN UPDATED MULTI-MEDIA WEB BRIEFING AVAILABLE
REGARDING THIS UPCOMING WINTER STORM ON THE WEBSITE
WWW.WEATHER.GOV/ABR UNDER THE TOP NEWS SECTION OF THE DAY PORTION
OF THE WEB-PAGE.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
THERE WILL BE A COUPLE OF ISSUES TO CONTEND WITH IN THE EXTENDED.
MODELS GENERALLY AGREE WITH THE ASPECT OF A MAJOR WINTER STORM
IMPACTING THE NORTHERN PLAINS WEDNESDAY NIGHT THROUGH FRIDAY
NIGHT. THE FIRST ISSUE CENTERS AROUND THE STRENGTH AND PLACEMENT
OF A SHORT WAVE DROPPING INTO THE REGION FROM THE NORTHWEST.
THE ECMWF IS MUCH STRONGER WITH THIS WAVE THEN ALL OTHER MODELS. IF
THE ECMWF VERIFIES...THEN POPS WILL NEED TO BE INCREASED ON FRIDAY
AND SATURDAY.

FOR NOW WILL LEAN TOWARDS THE 12Z GFS AND 0Z ECMWF FOR THIS
FORECAST PACKAGE. A LEAD H7 LOW TRACKS NORTHWARD FROM EASTERN KANSAS
AND INTO THE EXTREME EASTERN CWA BY THURSDAY AFTERNOON. THIS IS
THE WAVE THAT PRODUCES THE BEST LIFT AND FORCING OVER THE
SOUTHEASTERN CWA. EXPECT SNOWFALL RATES OF ONE TO TWO INCHES AN
HOUR OVER THE SOUTHEASTERN CWA AFTER MIDNIGHT WEDNESDAY NIGHT
BASED ON 10 MICRO-BARS OF OMEGA IN THE SNOW GROWTH REGION...AND
SPECIFIC HUMIDITY AROUND 3 G/KG. HOWEVER...THE NEXT ISSUE TO
CONTEND WITH WILL BE WHETHER OR NOT CONVECTION DEVELOPS ACROSS THE
SOUTHERN PLAINS. THIS COULD POTENTIALLY STEAL SOME OF THE MOISTURE
FOR THIS AREA.

EXPECT SNOW WILL CONTINUE DURING THE DAY ON FRIDAY...HOWEVER THE
INTENSITY MAY BE WEAKER ONCE THE SYSTEM OCCLUDES. SPECIFIC
HUMIDITY DOES REMAIN ABOVE 2 G/KG ONCE THE TROWAL WRAPS INTO THE
AREA. IDENTIFYING THE PLACEMENT OF THE TROWAL 96 HOURS IN ADVANCE
IS NEARLY IMPOSSIBLE SO WILL GO WITH BROAD BRUSH WITH QPF/SNOWFALL
AMOUNTS. WINDS INTENSIFY BY THURSDAY NIGHT OUT WEST...THEN SLOWLY
SPREADS EASTWARD DURING THE DAY ON FRIDAY. SUSTAINED WINDS OF 25
TO 35 MPH SEEM LIKELY WITH HIGHER GUSTS...BY FRIDAY AFTERNOON.
THERE IS A POSSIBILITY FOR THE WINTER STORM WARNING TO BE UPGRADED
TO A BLIZZARD WARNING...ESPECIALLY IN THE WESTERN CWA. WILL KEEP
THE WINTER STORM WARNING AS IS FOR NOW...AND KEEP A DECISION FOR
UPGRADING TO A BLIZZARD WARNING ON HOLD UNTIL AFTER FURTHER MODEL
REFINEMENT.

AT THIS TIME...PRECIPITATION APPEARS TO BE ENDING SOMETIME ON
FRIDAY NIGHT WITH THE POSSIBILITY OF LIGHT SNOW ON SATURDAY. WILL
LEAVE SATURDAY AND THE REST OF THE EXTENDED DRY FOR NOW. ONCE THIS
STORM SYSTEM FINALLY EXITS THE AREA...A BROAD AREA OF HIGH
PRESSURE WILL RULE THE NORTHERN PLAINS.

&&

.AVIATION...
18Z TAFS FOR KABR...KATY...KPIR AND KMBG

MVFR AND IFR CEILINGS ARE EXPECTED AT ALL TAF SITES THROUGH THE
NEXT 24 HOURS. A FEW FLURRIES AND SOME AREAS OF FOG WILL BE COMMON
OVER THE NEXT 24 HOURS AS WELL.

EXPECT WIDESPREAD LIGHT SNOW TO BEGIN OVERSPREADING THE REGION ON
WEDNESDAY. THE KPIR AND KMBG TERMINALS COULD SEE SNOW DEVELOPING
BY 18Z ON WEDNESDAY. THE KABR AND KATY TERMINALS WILL LIKELY SEE
SNOW DEVELOPING AT OR AFTER 00Z THURSDAY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WARNING FROM 6 PM CST /5 PM MST/ WEDNESDAY TO 6 PM 
     CST /5 PM MST/ FRIDAY 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 WEDNESDAY TO 6 PM CST FRIDAY FOR 
     BIG STONE-TRAVERSE.

&&

$$
SHORT TERM...DORN
LONG TERM...SD
AVIATION...DORN

WEATHER.GOV/ABERDEEN