FXUS63 KUNR 292140
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
240 PM MST SUN NOV 29 2009

.DISCUSSION...CURRENT SURFACE ANALYSIS SHOWS HIGH PRESSURE OVER THE 
CENTRAL ROCKIES...WITH WEST-NORTHWEST SURFACE FLOW IN PLACE ACROSS 
THE NORTHERN PLAINS. MORNING CLOUDS HAVE DISSIPATED ACROSS THE 
AREA...WITH MOSTLY SUNNY SKIES NOW. TEMPS ARE IN THE 40S AT MOST 
LOCATIONS. 

MILDER AND DRY WX WILL CONTINUE THROUGH MONDAY NIGHT...WITH ABOVE 
AVERAGE TEMPS PERSISTING. A COLDER PATTERN WILL BE IN PLACE DURING 
THE MIDDLE PART OF THE WEEK AFTER A COLD FRONT PASSAGE...WITH NEAR 
AVERAGE TEMPS EXPECTED...BUT STAYING MOSTLY DRY. 

FOR TONIGHT...SKIES WILL BE MOSTLY CLEAR WITH LIGHT WESTERLY WINDS. 
TEMPS WILL DROP TO THE 20S AT MOST LOCATIONS...WITH SOME TEENS IN 
VALLEY AREAS AND THE USUAL COLD SPOTS. WARMER AIR WILL BEGIN TO 
ADVECT IN LATER TONIGHT AND CONTINUE ON MONDAY. THIS WILL ALLOW 
TEMPS TO RISE NICELY ON MONDAY...WITH HIGHS MAINLY IN THE 50S. 
MOSTLY CLEAR CONDITIONS WILL CONTINUE INTO MONDAY NIGHT...WITH SOME 
INCREASING CLOUDS FROM THE NORTH AND WEST LATE. LOWS WILL DROP INTO 
THE 20S AND 30S. 

A STRONG COLD FRONT AND UPPER LEVEL SHORTWAVE WILL PASS THROUGH THE 
AREA TUESDAY MORNING. STRONG NORTHWEST WINDS WILL DEVELOP BEHIND THE 
FRONT AS CAA KICKS IN. AT THIS POINT...IT LOOKS LIKE AT LEAST A WIND 
ADVISORY EVENT FOR PORTIONS OF THE WESTERN SD PLAINS. NOT EXPECTING 
MUCH...IF ANY...PCPN WITH THIS FRONT AS ATMOSPHERE WILL REMAIN 
RATHER DRY. MAIN CHANCES FOR A FEW SNOW SHOWERS WILL BE ACROSS 
NORTHEASTERN WY AND POSSIBLY THE HILLS. HIGHS WILL BE IN THE 30S AND 
40S...WITH TEMPERATURES LIKELY FALLING LATER IN THE DAY. 

EXTENDED...TROUGH WILL SLIDE EAST OF THE CWA ON WEDNESDAY WITH RIDGE 
BUILDING ACROSS THE WEST COAST CREATING NORTHWEST FLOW AND COLDER 
TEMPERATURES ACROSS THE REGION. SUBTLE EMBEDDED SHORTWAVES MAY BRING 
FLURRIES TO PORTIONS OF NORTHWEST SOUTH DAKOTA AND NORTHEAST WYOMING 
DURING THE DAY. MODELS HAVE BEEN TRENDING DRIER WITH THESE WAVES SO 
HAVE KEPT POPS IN THE SLIGHT CHANCE CATERGORY. RIDGE WILL MOVE 
ACROSS THE CWA ON FRIDAY AS A TROUGH DIVES INTO THE PACIFIC 
NORTHWEST. SEVERAL GFS ENSEMBLE MEMBERS SHOW TROUGH DIGGING INTO THE 
WESTERN CONUS INTO THIS WEEKEND WHICH WOULD BRING SIGNIFICANTLY 
COLDER TEMPERATURES TO THE AREA. GEM ALSO LEANING TOWARD THIS 
SOLUTION. HOWEVER...THE ECMWF HAS A HIGH AMPLITUDE RIDGE SLIDING 
ACROSS THE AREA ON SATURDAY WITH TROUGH TURNING INTO AN UPPER LOW 
OVER SOUTHWEST CANADA...PLACING THE CWA IN QUASI ZONAL FLOW. IF THE 
GFS SOLUTION HOLDS...WE COULD SEE SOME SNOW ACROSS SOUTHERN PORTIONS 
OF THE CWA THIS WEEKEND AHEAD OF VERY COLD AIR SURGING SOUTHWARD 
FROM CANADA. RMOP INDICATING LOWER PREDICTABILITY WITH EVOLUTION OF 
TROUGH ACROSS THE AREA. GIVEN THE UNCERTAINTY...WILL KEEP HIGH TEMPS 
IN THE 30S AND DRY CONDITIONS GOING INTO NEXT WEEKEND.  
 
&&

.AVIATION...VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST 
PERIOD.    
 
&&

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

$$