FXUS63 KUNR 060331
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
831 PM MST SAT DEC 5 2009

.DISCUSSION...SFC PRESSURE RISES INDICATE ANOTHER COLD FRONT IS
CURRENTLY MOVING SOUTHWARD INTO THE FORECAST AREA FROM SERN MT AND
SWRN ND...RESULTING IN AREAS OF LIGHT SNOW AND MUCH COLDER
TEMPERATURES. THE PESKY LITTLE BAND OF SNOW THE DEVELOPED OVER
THE EASTERN BLACK HILLS TODAY AND SLID SLOWLY SOUTHWARD DURING THE
EVENING HAS NOW LOST MUCH OF IT/S INTENSITY AND HAD BROADENED INTO
AN AREA OF LIGHT SNOW OVER EASTERN CUSTER AND FALL RIVER...SHANNON
AND WESTERN PARTS OF JACKSON AND BENNETT COUNTIES. HAVE PREVIOUSLY
UPDATED FORECAST TO COVER THIS EXPECTED EVOLUTION BUT MAY HAVE TO
RAISE SNOW AMOUNTS A BIT MORE OVER THOSE AREAS IF THE SNOW BECOMES
MORE PERSISTENT AND INTENSE.

&&

.AVIATION...WIDESPREAD MVFR CONDITIONS EXPECTED OVERNIGHT WITH
AREAS OF FLURRIES OR LIGHT SNOW. LOCALIZED IFR CIGS/VSBYS
EXPECTED IN AREAS OF LIGHT SNOW.

&&

.PREV DISCUSSION... /ISSUED 219 PM MST SAT DEC 5 2009/ 

DISCUSSION...20Z SURFACE ANALYSIS HAS LOW PRESSURE CENTER OVER
HUDSON BAY AND ANOTHER OVER COLORADO...WITH COLD FRONT STRETCHING
BETWEEN THE TWO. UPPER LEVEL ANALYSIS HAS LOW IDAHO...SLOWLY
MOVING SOUTH. REGIONAL RADARS SHOWING SOME LIGHT SNOW SHOWERS
SCATTERED ACROSS THE AREA. TEMPERATURES ARE IN THE 20S AND LOWER
30S. 

VERY COLD AND UNSETTLED PATTERN WILL PERSIST ACROSS THE AREA FOR 
THE NEXT SEVERAL DAYS. ACTIVE FLOW WITHIN THE LARGE UPPER TROF
WILL BRING DAILY CHANCES FOR LIGHT SNOW TO MUCH OF THE AREA
THROUGH TUESDAY. BEST CHANCES LOOK TO BE TONIGHT INTO SUNDAY
ACROSS WESTERN AREAS...THEN AGAIN ACROSS MUCH OF THE AREA LATE
MONDAY INTO TUESDAY.

TONIGHT...CHANCES FOR SNOW SHOWERS WILL CONTINUE ACROSS MUCH OF
THE AREA AS UPPER LOW SETTLES ACROSS SOUTHERN IDAHO AND WEAKENS.
BEST CHANCES FOR SNOW WILL AGAIN BE ACROSS WESTERN
AREAS...ESPECIALLY THE NORTHERN HILLS...WHERE SOME UPSLOPE
ENHANCEMENT TO SNOW IS POSSIBLE. COULD SEE A COUPLE OF INCHES
ACCUMULATION TONIGHT ACROSS FAVORED TERRAIN OF THE NORTHWESTERN
HILLS. ACCUMULATIONS OF LESS THAN AN INCH ARE EXPECTED ELSEWHERE.
LOWS WILL DROP TO AROUND ZERO IN MANY LOCATIONS AS BRUNT OF ARCTIC
AIR BUILDS IN.

CHANCES FOR SNOW WILL PERSIST ON SUNDAY...WITH BETTER CHANCES 
SHIFTING TO SOUTHERN PORTIONS OF THE CWA AS WEAK MID LEVEL LOW
SLIDES ACROSS SOUTHERN NEBRASKA AND NORTHERN KANSAS. SOME LIGHT
ACCUMULATION IS POSSIBLE...MAINLY ALONG THE SOUTH DAKOTA AND
NEBRASKA BORDER AND ALSO ACROSS THE BLACK HILLS. TEMPS WILL NOT
BUDGE MUCH WITH CLOUD COVER AND ARCTIC AIR IN PLACE. HIGHS WILL BE
IN THE SINGLE DIGITS AND TEENS...WITH WIND CHILLS NEAR OR BELOW
ZERO.

CLOUDY AND COLD CONDITIONS WILL CONTINUE ON MONDAY AS ONE WAVE
MOVES EAST AND NEXT ONE SLIDES ACROSS THE ROCKIES. TEMPS ON MONDAY
WILL ONLY BE IN THE SINGLE DIGITS AND TEENS AGAIN. A MORE
WIDESPREAD CHANCE FOR SNOWFALL LOOKS POSSIBLE BY MONDAY NIGHT AS
NEXT WAVE APPROACHES IN SOUTHWEST FLOW ALOFT. COULD BE A DECENT
OVERRUNNING PCPN EVENT WITH SOME POTENTIAL FOR A FEW INCHES OF
FLUFFY ACCUMULATION ACROSS PARTS OF THE AREA...ESPECIALLY SOUTHERN
SD.

EXTENDED...AS STORM SYSTEM EXITS CENTRAL PLAINS AND UPPER TROF 
SWINGS ACROSS THE NORTHERN PLAINS...CHANCES OF SNOW WILL DIMINISH 
ACROSS SD TUES. ANOTHER SURFACE HIGH WILL DROP INTO THE PLAINS 
WED...WITH COLDER TEMPS FOR MID WEEK. FORECAST AREA REMAINS UNDER 
CYCLONIC NW FLOW ALOFT BEFORE TRANSITIONING TO MORE ZONAL FLOW NEXT 
WEEKEND...SO WILL KEEP LOW POPS IN FORECAST. TEMPS WILL BE NEAR 
NORMAL BY THE END OF THE WEEK.
 

&&

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

$$
GR