FXUS63 KUNR 151004
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
304 AM MST TUE DEC 15 2009

.DISCUSSION...09Z SURFACE ANALYSIS HAS ARCTIC HIGH OVER THE
NORTHERN GREAT PLAINS. TEMPERATURES RANGE FROM NEAR ZERO OVER
NORTHEAST WYOMING INTO THE BLACK HILLS...TO 20 BELOW ZERO ACROSS
NORTHWEST SOUTH DAKOTA. WINDS ARE LIGHT. SOME LIGHT SNOW SHOWERS
ARE CROSSING NORTHWEST AND WEST CENTRAL SOUTH DAKOTA ATTM
ASSOCIATED WITH WEAK WARM ADVECTION STRATO CU DECK. UPPER LEVEL
ANALYSIS HAS TROF SHIFTING EAST OF THE AREA...AND RIDGING BUILDING
INTO THE WESTERN CONUS.

FOR TODAY...COLD START TO THE DAY ACROSS THE SOUTH DAKOTA PLAINS
AS TEMPS HAVE PLUMMETED TO WELL BELOW ZERO IN MANY LOCATIONS.
CURRENT WIND CHILL ADVISORY LOOKS GOOD AND WILL CONTINUE UNTIL MID
MORNING...WHEN TEMPERATURES SHOULD MODERATE SOMEWHAT. WEAK SNOW
SHOWERS ASSOCIATED WITH STRATO CU DECK WILL LIFT NORTHEAST THIS
MORNING AS UPPER RIDGE BUILDS ACROSS THE ROCKIES. DECENT SOUTHWEST
BOUNDARY LAYER FLOW WILL PUSH TEMPS WELL INTO THE 30S ACROSS
NORTHEAST WYOMING...THE BLACK HILLS...AND FAR SOUTHWEST SOUTH
DAKOTA. TEMPS WILL REMAIN IN THE TEENS ACROSS THE PLAINS AS ARCTIC
AIR WILL BE TOUGH TO COMPLETELY SCOUR OUT.

TONIGHT...UPPER RIDGE SHIFTS FURTHER EAST. LOWS ACROSS THE PLAINS
WILL FALL TO AROUND ZERO IN SOME PLACES...BUT SHOULD REMAIN IN THE
SINGLE DIGITS IN GENERAL. TEENS AND 20S ARE EXPECTED ACROSS
NORTHEAST WYOMING AND THE BLACK HILLS.

WEDNESDAY...UPPER RIDGE SHIFTS INTO THE NORTHERN PLAINS. MILD
TEMPS EXPECTED FOR ALL...WITH READINGS IN THE 30S TO MID 40S UNDER
SUNNY SKIES.

THURSDAY...WEAK SHORTWAVE FLATTENS THE RIDGE...GIVING THE AREA A
CHANCE OF RAIN OR SNOW SHOWERS...MAINLY IN THE AFTERNOON. MILD
TEMPERATURES WILL BE FOUND EARLY...WITH TEMPERATURES COOLING BY
LATE AFTERNOON. A CHANCE OF SNOW IS EXPECTED THURSDAY NIGHT.

EXTENDED...LATEST MEDIUM GUIDANCE CONTINUES WITH UPPER LEVEL RIDGE 
OVER THE ROCKIES...BUT DIFFERS ON LOCATION/PLACEMENT OF UPPER LEVEL 
TROUGH OVER THE MIDWEST/GREAT LAKES. THE EXACT DETAILS COULD MAKE A 
BIG DIFFERENCE FOR TEMPERATURES ON THE SD PLAINS BY THE WEEKEND. 
WILL CONTINUE WITH FORECAST INERTIA SPICED BY THE LATEST ENSEMBLE 
TRENDS. CHANCE OF SNOW CONTINUES FRIDAY AS SYSTEM EXITS TO THE SOUTH 
AND EAST.

&&

.AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED WITH WITH A SC/AC 
DECK. ISOLATED POCKETS OF MVFR CIGS MAY OCCUR WITH ANY SHSN EARLY 
THIS MORNING.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WIND CHILL ADVISORY UNTIL 9 AM MST THIS MORNING FOR BUTTE-
     HARDING-NORTHERN MEADE CO PLAINS-PERKINS-ZIEBACH.

WY...NONE.
&&

$$