FXUS63 KABR 230325 AAA
AFDABR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
925 PM CST TUE DEC 22 2009

.UPDATE...
DID NOT MAKE ANY SIGNIFICANT CHANGES TO THE FORECAST THIS EVENING.
NOT MUCH GOING ON PRECIPITATION-WISE RIGHT NOW WITH MODELS SHOWING
LITTLE IN THE WAY OF FORCING. ONLY ECHOES ON THE RADAR ARE
CURRENTLY OVER WESTERN SOUTH DAKOTA...AND THEY ARE VERY LIGHT.
THEREFORE...REMOVED POPS FROM THE EASTERN CWA...BUT LEFT THEM IN
ACROSS THE WEST. ALSO PUT IN A MENTION OF PATCHY FOG AS MOST AREAS
SEEING SOME FOG. NEW AVIATION DISCUSSION BELOW.

&&
.PREV DISCUSSION...
.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 IN
HOURS OVER THE SOUTHEASTERN CWA AFTER MIDNIGHT ON WEDNESDAY 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 TROW-AL WRAPS INTO THE
AREA. IDENTIFYING THE PLACEMENT OF THE TROW-AL 96 HOURS IN ADVANCE
IS NEARLY IMPOSSIBLE SO WILL GO WITH BROAD BRUSH WITH QPF/SNOWFALL
AMOUNTS. WINDS INTENSIFY THURSDAY NIGHT OUT WEST...THEN SLOWLY
SPREADS EASTWARD DURING THE DAY ON FRIDAY. SUSTAINED WINDS OF 25 TO
35 MPH SEEMS 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.

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...
IFR TO LOWER LEVEL MVFR CIGS WILL REMAIN ACROSS THE ENTIRE CWA
THROUGH THE OVERNIGHT HOURS. PATCHY FOG WILL ALSO BE COMMON..BUT
VSBYS ARE NOT EXPECTED TO FALL BELOW ONE MILE. LOOK FOR LIGHT SNOW
TO BEGIN OVERSPREADING THE AREA ON WEDNESDAY...BEGINNING ACROSS
THE WESTERN AND SOUTHERN CWA DURING THE MID TO LATE AFTERNOON
HOURS.

&&

.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.

&&

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

WEATHER.GOV/ABERDEEN