RSS FeedsIssued by NWS Rapid City, SD
000 FXUS63 KUNR 250350 AFDUNR AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 850 PM MST TUE NOV 24 2009 .DISCUSSION...RAIN AND SNOW SHOWERS HAVE DEVELOPED ACROSS PORTIONS OF THE CWA THIS EVENING ALONG WITH GUSTY NORTHWEST WINDS. A PERSISTENT BAND OF RAIN AND SNOW HAS SET UP FROM NORTHEAST CROOK COUNTY STRETCHING INTO FAR EASTERN PENNINGTON COUNTY. EXPECT THIS BAND TO MOVE SOUTHWARD THIS EVENING AND DIMINISH IN INTENSITY. EXPECT LITTLE SNOW ACCUMULATION WITH THIS ACTIVITY. HAVE INCREASED POPS ACROSS THE CWA FOR THE REST OF TONIGHT. THE REST OF THE FORECAST IS ON TRACK. && PREV DISCUSSION... /ISSUED 237 PM MST TUE NOV 24 2009/ DISCUSSION...21Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE NORTHERN ROCKIES WITH LOW PRESSURE EXTENDING FROM SASKATCHEWAN/MANITOBA THROUGH MINNESOTA TO A COMPACT LOW PRESSURE CENTER OVER IOWA. UPPER ANALYSIS SHOWS A RIDGE OVER THE PACIFIC COAST WITH A TROUGH DIVING RAPIDLY SOUTHWARD OUT OF THE CANADIAN PRAIRIE PROVINCES. NAM DEPICTS A 120KT JET STREAK ALONG THE WEST SIDE OF THE UPPER TROUGH HEADING SWRD ACROSS ERN MONTANA ATTM. A COLD FRONT WILL RACE ACROSS THE CWA THIS EVENING WITH BREEZY SPOTS AHEAD OF AND BEHIND THE FRONT. MOISTURE WILL BE LIMITED...BUT THERE WILL BE ENOUGH FORCING FOR SOME SNOW SHOWERS ACROSS THE AREA. THE BEST CHANCE OF ANY ACCUMULATING SNOW WILL BE LOCATED FROM THE BIGHORNS ACROSS NERN WYOMING TO FAR SWRN SOUTH DAKOTA...INCLUDING THE BLACK HILLS. THIS IS THE AREA WHERE THE STRONGEST UPPER DIVERGENCE ASSOCIATED WITH THE JET STEAK...WILL BE OVERRUNNING THE AREA OF STRONGEST MID LEVEL FRONTOGENESIS. DUE TO THE LIMITED AVAILABLE MOISTURE HAVE ADDED RELATIVELY HIGH POPS AND LOW QPF TO THOSE AREAS TONIGHT...WITH ANY SNOW ACCUMULATIONS EXPECTED TO BE LESS THAN AN INCH. WEDNESDAY WILL FEATURE BREEZY AREAS WITH LOW LEVEL COLD AIR ADVECTION IN THE MORNING...BUT THIS WILL BE REPLACED BY WARM AIR ADVECTION LATER IN THE DAY AS UPPER RIDGE BUILDS OVER THE ROCKIES. COOLER TEMPERATURES EXPECTED. ON THURSDAY...AN UPPER RIDGE BUILDS OVER THE PLAINS AS ANOTHER UPPER LEVEL TROUGH CRASHES INTO THE PACIFIC NORTHWEST. SEASONABLY PLEASANT WEATHER IS EXPECTED FOR THANKSGIVING DAY. EXTENDED...UPPER RIDGE WILL KEEP WARM AND DRY CONDITIONS OVER THE AREA THROUGH FRIDAY. STRONG UPPER LEVEL TROF WILL SLIDE ACROSS THE ROCKIES AND INTO THE PLAINS FRIDAY NIGHT INTO SATURDAY. THIS WILL BRING A SLIGHT CHANCE FOR PRECIPITATION ALONG WITH COOLER TEMPERATURES AND BREEZY NORTHWEST WINDS FOR THE WEEKEND. WEAK RIDGING IS EXPECTED ON MONDAY WITH DRY CONDITIONS AND NEAR NORMAL TEMPERATURES. && .AVIATION...COLD FRONT SWEEPING ACRS FCST AREA TONIGHT. GUSTY NW WNDS HAV DVLPD AND WL CONT TIL EARLY MRNG. WHILE CONDITIONS WL RMN MOSTLY VFR WITH CIGS 4-6K...LOCAL MVFR CIGS AND VSBYS IN LGT SNW SHWRS WL OCCUR OVERNIGHT AS UPPER SYSTEM MOVES THROUGH THE NRN PLNS. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...NONE. WY...NONE. && $$ JW/SS
