FXUS63 KUNR 090955
AFDUNR

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

.DISCUSSION...CURRENT SURFACE ANALYSIS SHOWS LOW PRESSURE OVER
NORTHERN IL...WITH ARCTIC HIGH PRESSURE OVER THE NORTHERN ROCKIES.
UPPER LEVEL ANALYSIS HAS TROF STRETCHING FROM THE ROCKIES INTO THE
GREAT LAKES REGION...WITH STRONG WINTER STORM OVER THE UPPER
MIDWEST AND SHORTWAVE ENERGY ACROSS THE CANADA PRAIRIE PROV. SKIES
HAVE CLEARED ACROSS NORTHEASTERN WY AND FAR WESTERN SD. SKIES ARE
MAINLY CLOUDY OVER EASTERN PORTIONS OF THE AREA WITH A FEW FLURRIES
LINGERING. WHERE SKIES HAVE CLEARED...TEMPS HAVE FALLEN
RAPIDLY...WITH TEMPS NEAR 20 BELOW ACROSS PARTS OF NORTHEAST WY
AND THE HILLS. FURTHER EAST...TEMPS ARE NEAR OR BELOW ZERO.
NORTHWESTERLY WINDS OF 5 TO 15 MPH...A BIT HIGHER TOWARD CENTRAL
SD...ARE PRODUCING WIND CHILLS IN THE 15 BELOW TO 30 BELOW ZERO
RANGE RIGHT NOW.

BITTER COLD AIR WILL REMAIN IN PLACE THROUGH AT LEAST THURSDAY AS
ARCTIC HIGH SETTLES OVER THE ROCKIES AND WEAKENS. NORTHWEST FLOW
ALOFT WILL KEEP COLD AIR IN PLACE WITH VARIABLY CLOUDY CONDITIONS.
UPPER LEVEL ENERGY IMBEDDED IN THE FLOW COULD ALLOW SOME FLURRIES
TO DEVELOP TONIGHT AND THURSDAY ACROSS NORTHERN AND WESTERN
PORTIONS OF THE CWA.

FOR TODAY...SKIES WILL BE VARIABLY CLOUDY WITH HIGHS ONLY IN THE
SINGLE DIGITS. CLOUDS FROM SYSTEM TO THE EAST WILL EXIT EASTERN
AREAS THIS MORNING...WHILE CLOUDS WILL LIKELY INCREASE SOME FROM
THE WEST THIS AFTERNOON AS WEAK WAVE APPROACHES. WIND CHILLS THIS
MORNING WILL MOSTLY BE IN THE 20 BELOW TO 35 BELOW ZERO RANGE.
WILL KEEP WIND CHILL ADVISORY GOING THROUGH THE MORNING.

A FEW FLURRIES ARE POSSIBLE ACROSS NORTHEASTERN WY AND
NORTHWESTERN SD TONIGHT AND THURSDAY AS UPPER LEVEL WAVE CLIPS
THE AREA. BRISK WINDS ACROSS NORTHERN AREAS WILL PRODUCE BITTER
WIND CHILLS AGAIN TONIGHT INTO THURSDAY MORNING. WILL LIKELY NEED
TO ISSUE ANOTHER WIND CHILL ADVISORY LATER TODAY FOR PORTIONS OF
THE CWA AS TEMPS DROP BELOW ZERO AGAIN TONIGHT. WILL SEE A LITTLE
BIT OF A WARMUP ON THURSDAY AS WESTERLY WINDS SHOULD HELP TO MIX
OUT THE LOWER ATMOS A BIT. HIGHS SHOULD GET INTO THE TEENS AT MOST
LOCATIONS...WITH SOME SINGLE DIGITS LINGERING ACROSS NORTHERN AND
EASTERN PORTIONS OF THE CWA.

WILL CONTINUE TO SEE SOME MODERATION IN TEMPS ON FRIDAY...
ESPECIALLY ACROSS NORTHEAST WY AND THE HILLS...AS ARCTIC BOUNDARY
TRIES TO MOVE EAST FROM THE ROCKIES. AREAS NORTH AND EAST OF THE
HILLS WILL ONLY SEE A MINIMAL WARMUP. HIGHS FRIDAY SHOULD GET INTO
THE 20S ACROSS NORTHEAST WY AND THE HILLS...WHILE AREAS TO THE
NORTH AND EAST WILL LIKELY STRUGGLE TO GET INTO THE TEENS.

EXTENDED...LOW CONFIDENCE OVER THE WEEKEND INTO EARLY NEXT WEEK AS 
MODELS LACKING RUN TO RUN CONSISTENCY AND ENSEMBLES SHOWING A BROAD  
SPREAD. LARGE UPPER TROUGH REMAINS OVER MUCH OF CANADA. 
WEST-NORTHWEST FLOW ACROSS THE AREA...WITH SEVERAL EMBEDDED 
SHORTWAVES. GFS/GEM/ECMWF SHOWING SIGNS OF WEAK SURFACE LOW MOVING 
ACROSS THE AREA SATURDAY NIGHT/SUNDAY...WITH ARCTIC BOUNDARY 
BISECTING THE FORECAST AREA. APPEARS THAT THERE WILL BE WARMING IN 
THE 850-700MB LAYER...QUESTION REMAINS AS TO HOW MUCH SURFACE 
TEMPERATURES MODERATE. WITH CLOUDS...LACK OF MIXING...AND NEW SNOW 
COVER...WILL KEEP TEMPERATURES ON THE LOW END OF GUIDANCE. WARMEST 
TEMPERATURES LIKELY TO BE IN HIGHER ELEVATIONS OF BLACK HILLS. 

&&

.AVIATION...MVFR CIGS ACROSS SW/SC SD WITH LIGHT SNOW/FLURRIES WILL 
END THIS MORNING. OTHERWISE VFR CONDITIONS EXPECTED THROUGH THE DAY 
WITH SCT-BKN CLOUDS 5000-7000 FT AGL. 

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY UNTIL NOON MST /1 PM CST/ TODAY 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 UNTIL NOON MST TODAY FOR NORTHEASTERN CROOK-
     NORTHERN CAMPBELL-SOUTHERN CAMPBELL-WESTERN CROOK-WESTON-
     WYOMING BLACK HILLS.

&&

$$