FXUS63 KUNR 092148
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
248 PM MST WED DEC 9 2009

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A BROAD UPPER TROUGH SLOWLY 
CROSSING MUCH OF THE CONUS WITH NORTHWESTERLY FLOW ALOFT ACROSS THE 
CWA. SURFACE OBS SHOW TEMPERATURES BARELY MAKING IT ABOVE ZERO 
DEGREES AT MOST LOCATIONS. A SERIES OF WEAK SHORTWAVES WILL CROSS 
THE CWA TONIGHT BRINGING AN INCREASE IN CLOUDS AND WINDS. PARTS OF 
NORTHWEST SOUTH DAKOTA AND NORTHEAST WYOMING COULD SEE FLURRIES 
DEVELOP OVERNIGHT. THE BIGGEST CONCERN WILL BE WITH WIND CHILLS. 
WESTERLY WINDS ARE EXPECTED TO INCREASE OVERNIGHT WHICH WILL COMBINE 
WITH TEMPS BELOW ZERO...RESULTING IN WIND CHILLS APPROACHING 20 TO 
30 BELOW ZERO. SO WILL REISSUE A WIND CHILL ADVISORY FOR TONIGHT 
THROUGH NOON MST THURSDAY.

WARMER AIR WILL BEGIN WORKING ITS WAY BACK INTO THE REGION THURSDAY 
AS THE UPPER FLOW VERY GRADUALLY TRANSITIONS INTO A MORE ZONAL 
PATTERN HEADING INTO THE WEEKEND. HIGHS ARE EXPECTED TO REACH THE 
TEENS TOMORROW...BUT WITH WESTERLY WINDS BLOWING AT 15 TO 20 MPH 
ACROSS MOST LOCATIONS...THE WARMEST WIND CHILLS WILL BE ARE AROUND 
ZERO DURING THE AFTERNOON HOURS. AS THE SERIES OF WAVES CONTINUE TO 
CROSS THE CWA...FLURRIES WILL STILL BE POSSIBLE ACROSS NORTHWEST 
SOUTH DAKOTA...THROUGH THE BLACK HILLS...INTO NORTHEAST 
WYOMING...DIMINISHING THURSDAY NIGHT. WIND CHILLS SHOULD NOT BE AN 
ISSUE AGAIN THURSDAY NIGHT GIVEN THE RELATIVELY WEAK WINDS AND 
WARMER OVERNIGHT LOWS. A QUIET DAY IS EXPECTED FRIDAY WITH PARTLY 
CLOUDY SKIES AND NO PRECIP IN THE FORECAST. WARMER AIR ADVECTION 
WILL CONTINUE WITH HIGHS REACHING THE MID TO UPPER TEENS ACROSS MUCH 
OF THE SOUTH DAKOTA PLAINS...AND 20S INTO NORTHEAST WYOMING...THE 
BLACK HILLS...AND SOUTHWEST SOUTH DAKOTA.

EXTENDED...MODELS CONTINUE TO SHOW AN UNSETTLED PATTERN THIS 
WEEKEND...PARTICULARLY ON SUNDAY AS A FAST MOVING SHORT WAVE SLIDES 
THROUGH. MODELS THEN DIVERGE ON TEMPERATURES FOR THE UPCOMING 
WEEK...AS ECWMF LEANS TOWARDS A WARMING TREND...AND GFS KEEPS COOLER 
AIR IN PLACE. AT THIS TIME HAVE GONE WITH A WEAK WARMING TREND AND 
WILL WILL SEE HOW MODELS HANDLE THIS OVER THE NEXT FEW RUNS.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY FROM 6 PM MST /7 PM CST/ THIS EVENING TO 
     NOON MST /1 PM CST/ THURSDAY FOR BENNETT-BUTTE-CENTRAL 
     BLACK HILLS-CUSTER CO PLAINS-FALL RIVER-HAAKON-HARDING-
     HERMOSA FOOT HILLS-JACKSON-MELLETTE-NORTHERN BLACK HILLS-
     NORTHERN FOOT HILLS-NORTHERN MEADE CO PLAINS-PENNINGTON CO 
     PLAINS-PERKINS-RAPID CITY-SHANNON-SOUTHERN BLACK HILLS-
     SOUTHERN FOOT HILLS-SOUTHERN MEADE CO PLAINS-
     STURGIS/PIEDMONT FOOT HILLS-TODD-TRIPP-ZIEBACH.

WY...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO NOON MST THURSDAY 
     FOR NORTHEASTERN CROOK-NORTHERN CAMPBELL-SOUTHERN CAMPBELL-
     WESTERN CROOK-WESTON-WYOMING BLACK HILLS.

&&

$$

CALDERON/SCHILD