FXUS63 KUNR 231007
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
300 AM MST WED DEC 23 2009

.DISCUSSION...CURRENT SURFACE ANALYSIS PLACES LOW PRESSURE OVER THE 
FOUR CORNERS REGION WITH INVERTED TROF STRETCHING UP THROUGH THE 
ROCKIES INTO NRN PLAINS...WHILE HIGH REMAINS OVER ONTARIO. COLD 
FRONT NOW SLIDING THROUGH NORTHERN MONTANA.  UPPER LEVEL ANALYSIS 
PLACES CENTER OF LOW PUSHING FROM NORTHEAST ARIZONA INTO NORTHWEST 
NEW MEXICO...WHILE SECONDARY LOW NOW SLIDING SOUTH THROUGH ALBERTA. 
SOME AREAS OF SNOW DEVELOPING OVER WRN SODAK INTO NERN WYO WITH 
INITIAL WAVE SLIDING THROUGH. FORECAST PROBLEM WILL BE DEALING WITH 
CHANGING MODEL SOLUTIONS...BOTH IN PRECIP AMOUNTS AND IN TIMING.

FOR TODAY...SOUTHERN UPPER LOW PUSHES EASTERLY TOWARDS TEXAS WHILE 
SECONDARY LOW DIVES SOUTH SLIDING INTO MONTANA. SNOW WILL CONTINUE 
DEVELOPING FROM WEST TO EAST AS BROAD AREA OF LIFT SPREADS ACROSS 
THE AREA THROUGH THE DAY. COLD FRONT WILL SAG SOUTH THROUGH THE 
DAY...WITH WINDS SHIFTING NORTHERLY AROUND MID-DAY. THIS SHOULD 
SCOUR OUT THE FOG THAT HAS BEEN PLAGUING THE ERN/NRN FOOTHILLS. 
EXPECTED SNOWFALL AMOUNTS ARE LOWER OVER THE WRN CWFA AS PRIMARY 
LIFT WILL BE FURTHER EAST...SO WILL CONVERT WATCH TO AN ADVISORY. 
WILL KEEP WARNING GOING OVER THE HILLS DUE TO UPSLOPE SNOWS 
DEVELOPING.

ON THURSDAY...NORTHERN LOW PUSHES INTO EASTERN WYOMING AROUND 
MID-DAY...BEFORE MERGING WITH SOUTHERN LOW AROUND KANSAS OVERNIGHT. 
WITH THIS PATTERN...IT WOULD SUGGEST A LULL IN PRECIPITATION DURING 
THE DAY UNTIL MERGED LOW BRINGS WRAP AROUND PRECIP BACK INTO THE 
AREA TOWARDS EVENING. WITH THAT SAID...TIGHTENING PRESSURE GRADIENT 
OVER THE AREA WILL BRING GUSTY NORTHWESTERLY WINDS. SO...ANY SNOW 
THAT IS ON THE GROUND MAY BE BLOWING AROUND REDUCING VISIBILITIES. 
TEMPERATURES WILL BE FRIGID AS CORE OF COLD AIR PULLS DOWN OVER THE 
AREA AS IT WRAPS INTO THE SYSTEM.

FOR FRIDAY...STACKED LOW MOVES OVER IOWA BEFORE SLOWLY MEANDERING 
OFF TO THE EAST. PRECIP WILL CONTINUE TO WRAP OVER THE SYSTEM INTO 
THE CWFA WHILE GUSTY NORTHWESTERLY WINDS CONTINUE....WHICH WILL 
CONTINUE TO PRODUCE AREAS OF BLOWING SNOW. THERE IS STILL SOME 
QUESTION ON HOW FAST THE SYSTEM EXITS...SO WILL HAVE TO KEEP A CLOSE 
EYE ON HOW THE NEXT MODEL RUNS REACT.  HAVE EXTENDED HEADLINES OVER 
THE SODAK PLAINS/BLKHLS TO ADDRESS SNOW/BLOWING SNOW THROUGH FRIDAY 
AFTERNOON.

EXTENDED...UPPER LEVEL LOW SHIFTS EAST ON SATURDAY AS CLOUD COVER 
DECREASES FROM WEST TO EAST. UPPER RIDGE WILL BEGIN TO BUILD INTO 
THE NORTHERN PLAINS ON SUNDAY AND MONDAY. WITH WEAK WAA ALOFT BOTH 
DAYS...TEMPERATURES SHOULD BEGIN TO SLOWLY WARM...ESPECIALLY IN 
NORTHEASTERN WYOMING AND OVER THE BLACK HILLS. DRY CONDITIONS ARE 
EXPECTED DURING THE WEEKEND INTO EARLY NEXT WEEK.

&&

.AVIATION...IFR/LIFR CONDITIONS WILL CONTINUE ACROSS MUCH OF THE 
AREA THIS MORNING DUE TO CIGS/FOG. BY LATE THIS MORNING...SNOW WILL 
BE DOMINATE WEATHER CONCERN WITH IFR VIS/CIGS CONTINUING THROUGH 
TONIGHT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...WINTER STORM WARNING UNTIL 5 PM MST FRIDAY FOR CENTRAL BLACK 
     HILLS-NORTHERN BLACK HILLS-SOUTHERN BLACK HILLS.

     WINTER STORM WARNING FROM 11 AM MST /NOON CST/ THIS MORNING TO
     5 PM MST /6 PM CST/ FRIDAY FOR BENNETT-HAAKON-JACKSON-  
     MELLETTE-TODD-TRIPP-ZIEBACH.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST FRIDAY FOR BUTTE-CUSTER 
     CO PLAINS-FALL RIVER-HARDING-HERMOSA FOOT HILLS-NORTHERN 
     FOOT HILLS-NORTHERN MEADE CO PLAINS-PENNINGTON CO PLAINS-
     PERKINS-RAPID CITY-SHANNON-SOUTHERN FOOT HILLS-SOUTHERN 
     MEADE CO PLAINS-STURGIS/PIEDMONT FOOT HILLS.

WY...WINTER STORM WARNING UNTIL 5 PM MST FRIDAY FOR WYOMING 
     BLACK HILLS.

     WINTER WEATHER ADVISORY UNTIL 5 PM MST FRIDAY FOR NORTHEASTERN 
     CROOK.

     WINTER WEATHER ADVISORY UNTIL 5 AM MST THURSDAY FOR NORTHERN 
     CAMPBELL-SOUTHERN CAMPBELL-WESTERN CROOK-WESTON.
&&

$$