FXUS63 KUNR 252200
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
300 PM MST FRI DEC 25 2009

.DISCUSSION...THE BLIZZARD RAGES ON ACROSS MUCH OF THE NORTHERN AND 
CENTRAL PLAINS. CURRENT SURFACE ANALYSIS SHOWS INTENSE LOW PRESSURE 
OVER WESTERN IA...WITH ARCTIC HIGH PRESSURE OVER ALBERTA. UPPER 
LEVEL ANALYSIS HAS AREAS OF LOW PRESSURE CONVERGING OVER NORTHERN MO 
AND IA. STRONG UPPER LEVEL ENERGY IS ROTATING WESTWARD AROUND THE 
LOW ACROSS THE DAKOTAS...NEBRASKA...AND INTO EASTERN WY AND MT. 
WINDS ARE STRONGEST ACROSS THE SD PLAINS...WHERE GUSTS OVER 60 MPH 
ARE BEING RECORDED ACROSS PARTS OF NORTHWEST AND WEST CENTRAL SD. 
TEMPS ARE IN THE SINGLE DIGITS AND LOWER TEENS...WITH WIND CHILLS OF 
10 BELOW TO 25 BELOW ZERO. LOCAL RADAR SHOWING SNOW ACROSS THE 
ENTIRE AREA...WITH THE HEAVIEST SNOW BANDS ACROSS THE CHEYENNE RIVER 
VALLEY...PARTS OF NORTHWESTERN SD...AND THE NORTHERN HILLS. SEVERAL 
INCHES OF SNOW HAVE FALLEN WHERE THESE HEAVIER BANDS HAVE SET 
UP...OTHERWISE GENERALLY AN INCH OR TWO HAS FALLEN SO FAR. VSBYS ARE 
AT OR BELOW A QUARTER MILE ACROSS MUCH OF THE SD PLAINS WITH BLOWING 
AND DRIFTING SNOW OCCURRING.   

STORM SYSTEM WILL CONTINUE TO BRING BLIZZARD OR NEAR BLIZZARD 
CONDITIONS ACROSS MOST OF WESTERN SD THROUGH TONIGHT AND INTO 
SATURDAY. FURTHER SOUTH AND WEST INTO FAR SOUTHWESTERN SD AND 
NORTHEASTERN WY...SNOW AND WIND WILL BE LIGHTER FOR THE MOST 
PART...BUT TREACHEROUS CONDITIONS CAN BE EXPECTED AS WELL. AS WARMER 
AIR ALOFT ADVECTS INTO THE AREA THIS AFTERNOON AND TONIGHT... 
ATMOSPHERE WILL BECOME MORE FAVORABLE FOR SNOWFLAKE GROWTH AND 
THEREFORE HIGHER SNOWFALL RATES ACROSS THE SD PLAINS AND INTO THE 
NORTHERN HILLS AREA. WINDS WILL DECREASE A BIT OVERNIGHT AND SNOW 
MAY LIGHTEN UP IN INTENSITY AND COVERAGE AT TIMES LATER TONIGHT INTO 
SATURDAY...BUT THE BLIZZARD TO NEAR BLIZZARD CONDITIONS WILL 
CONTINUE ACROSS THE WARNED AREAS.    

SYSTEM WILL BE SLOW TO EXIT LATER SATURDAY AND SATURDAY NIGHT AS LOW 
STALLS OVER THE WESTERN GREAT LAKES AREA. UPSLOPE SNOWFALL OVER THE 
NORTHERN HILLS WILL PERSIST RIGHT INTO SATURDAY NIGHT. SOME LIGHT 
SNOW IS ALSO LIKELY TO LINGER ACROSS EASTERN PORTIONS OF THE CWA 
INTO SATURDAY NIGHT AND POSSIBLY SUNDAY AS WELL...BUT WINDS WILL 
GRADUALLY DECREASE AT MOST LOCATIONS SATURDAY NIGHT.

FOR SNOWFALL TOTALS...WILL GO WITH 3 TO 7 INCHES ACROSS FAR 
SOUTHWESTERN SD AND SOUTHERN AND WESTERN PARTS OF NORTHEASTERN WY. 
THE REST OF THE PLAINS...ESPECIALLY ACROSS WESTERN SD...WILL 
GENERALLY SEE 8 TO 15 INCHES OF SNOWFALL...HIGHEST AMOUNTS ACROSS 
RIDGES AND PARTS OF NORTHWESTERN SD...WITH SIGNIFICANT BLOWING AND 
DRIFTING. ACROSS THE NORTHERN HILLS AREA...1 TO 2 FEET OF SNOW IS A 
GIVEN...WITH SOME AREAS EASILY EXCEEDING 2 FEET.  

EXTENDED...UPPER RIDGE ACROSS THE AREA MONDAY. HOWEVER STRONG 
INVERSION WILL KEEP TEMPERATURES BELOW AVERAGE. SLIGHT WARMING ON 
TUESDAY/WEDNESDAY...WITH WARMEST TEMPERATURES NORTHEAST WYOMING AND 
BLACK HILLS. EXTENDED MODELS INDICATING UPPER TROF DROPPING OUT OF 
CANADA MID-WEEK...SOME LIGHT SNOW POSSIBLE WITH COLD FRONT WEDNESDAY 
NIGHT INTO THURSDAY. TEMPERATURES WELL BELOW AVERAGE FOR THE END OF 
THE WEEK AS ANOTHER 1040MB ARCTIC HIGH DROPS INTO THE NORTHERN 
PLAINS. 

&&

.AVIATION...WIDESPREAD IFR/LIFR VSBY EXPECTED THROUGH THE NIGHT WITH 
SNOW AND BLOWING SNOW. 

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...BLIZZARD WARNING UNTIL 5 PM MST/6 PM CST SATURDAY FOR THE
     PLAINS OF WESTERN SOUTH DAKOTA AND NRN/ERN FOOTHILLS.
     WINTER STORM WARNING UNTIL 5 PM MST SATURDAY FOR THE NRN
     AND CNTRL BLKHLS.
     WINTER WEATHER ADVISORY UNTIL 5 PM MST SATURDAY FOR SRN
     BLKHLS AND EXTREME SWRN SD.
WY...BLIZZARD WARNING UNTIL 5 PM MST SATURDAY FOR NERN CROOK
     COUNTY.
     WINTER STORM WARNING UNTIL 5 PM MST SATURDAY FOR WYOMING
     BLKHLS AND CROOK COUNTY PLAINS.
     WINTER WEATHER ADVISORY UNTIL 5 PM MST SATURDAY FOR 
     CAMPBELL AND WESTON COUNTIES.

&&

$$