FXUS63 KUNR 102129
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
230 PM MST THU DEC 10 2009

.DISCUSSION...WATER VAPOR IMAGERY SHOWS A BROAD TROUGH ACROSS MUCH 
OF THE CONUS WITH A SERIES OF WAVES OVER MONTANA AND NORTH INTO 
CANADA DROPPING DOWN FROM THE NORTHWEST. VIS SAT SHOWS MOSTLY SUNNY 
SKIES WITH SOME MID LEVEL CLOUDS STREAMING THROUGH NORTHWEST SOUTH 
DAKOTA. PLENTY OF SUNSHINE TODAY HAS HELPED TEMPS TO RISE INTO THE 
UPPER TEENS TO LOWER 20S ACROSS THE PLAINS...AND MID 20S ACROSS THE 
EASTERN FOOTHILLS WHERE DOWNSLOPING WAS OCCURRING. AS FOR 
TONIGHT...QUIET WEATHER WILL CONTINUE ACROSS THE AREA. A FEW SITES 
OVER EASTERN MONTANA/WESTERN NORTH DAKOTA WERE REPORTING 
FLURRIES/LIGHT SNOW...BUT IT LOOKS LIKE THE AIR OVER NORTHWEST SOUTH 
DAKOTA WILL BE TOO DRY FOR ANY PRECIP TO MAKE IT FARTHER SOUTH.  
OTHERWISE MOSTLY CLEAR/PARTLY CLOUDY SKIES ARE EXPECTED WITH LOWS 
DROPPING TO 5 BELOW TO 5 ABOVE ZERO ACROSS MOST LOCATIONS.

MODELS CONTINUE TO SHOW THE CYCLONIC FLOW ALOFT TRANSITIONING INTO A 
MORE ZONAL TYPE PATTERN HEADING INTO THE WEEKEND. WARMER AIR WILL 
CONTINUE TO ADVECT OVERNIGHT TONIGHT INTO FRIDAY WITH HIGHS REACHING 
THE 20S ACROSS NORTHWEST AND CENTRAL SOUTH DAKOTA...AND LOWER 30S 
ACROSS SOUTHWEST SOUTH DAKOTA THROUGH THE BLACK HILLS INTO NORTHEAST 
WYOMING. MOSTLY SUNNY TO PARTLY CLOUDY SKIES ARE FORECAST FOR THE 
AREA. ANOTHER QUIET DAY IS EXPECTED SATURDAY...WITH TEMPERATURES 
WARMER THAN FRIDAY. MODELS SHOW A SHORTWAVE OVER IDAHO MOVING 
EASTWARD WITHIN THE ZONAL FLOW...WITH A DEVELOPING UPPER LOW OVER 
THE NORTHWEST PACIFIC COAST. THE WAVE IS PROGGED TO APPROACH THE CWA 
LATE SATURDAY...POSSIBLY BRINGING SOME SNOW TO NORTHEASTERN WYOMING 
AND FAR WESTERN SOUTH DAKOTA. IT IS POSSIBLE THE LOWER LEVELS WILL 
BE TOO DRY TO SUPPORT ANY PRECIP...BUT WILL LEAVE IN THE SLIGHT 
CHANCE POPS FOR NOW IN CASE TRENDS SUGGEST A FASTER WAVE OR BETTER 
AVAILABLE MOISTURE. HAVE REMOVED ALL POPS FOR EARLIER SATURDAY 
HOWEVER. THE BETTER CHANCES FOR PRECIP WILL BE AFTER SATURDAY NIGHT 
IN THE LONG TERM FORECAST.

EXTENDED...NEXT SHOT OF ARCTIC AIR IS SET TO ARRIVE LATE 
SUNDAY...WITH ALL THE 12Z GUIDANCE IN GOOD AGREEMENT. EXPECT THERE 
WILL BE ENOUGH MOISTURE TO COMBINE WITH THE INTENSE COLD ADVECTION 
TO PRODUCE SOME LIGHT SNOW ACROSS THE AREA SO HAVE BOOSTED POPS FOR 
SUNDAY NIGHT INTO MONDAY. THIS SHOT OF COLD AIR SHOULD BE SHORT 
LIVED...THOUGH...AS UPR RIDGE WILL BE QUICK TO REBUILD INTO THE NRN 
ROCKIES. TEMPS COULD WARM TO ABOVE AVERAGE READINGS TOWARDS THE 
MIDDLE/END OF NEXT WEEK.

&&

.AVIATION...VFR CONDITIONS NEXT 24 HOURS.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

CALDERON/JOHNSON