659
FXUS63 KUNR 090945
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
245 AM MST TUE FEB 9 2010
DISCUSSION
09Z SURFACE MAP SHOWS HIGH PRESSURE AXIS ACROSS THE
WESTERN DAKOTAS. FRIGID TEMPERATURES HAVE SETTLED OVER THE AREA
WITH MOST READINGS ZERO TO 10 BELOW ZERO. BROKEN DECK OF LOW
CLOUDS FROM WESTERN NORTH DAKOTA INTO WESTERN AND CENTRAL SOUTH
DAKOTA HAVE KEPT TEMPERATURES FROM PLUMMETING LOWER. NORTHWEST
WINDS HAVE DIMINISHED CONSIDERABLY...SO WIND CHILL ADVISORY HAS
BEEN CANCELLED. UPPER LEVEL ANALYSIS HAS COMPACT LOW MOVING INTO
NORTHERN MISSOURI...WITH WESTERN RIDGE SLOWLY SHIFTING EAST.
FOR TODAY...ARCTIC AIR WILL BE SLOW TO MOVE OUT OF THE SOUTH
DAKOTA PLAINS. HIGHS WILL LIKELY ONLY RECOVER INTO THE TEENS
TODAY. WARMER TEMPERATURES WILL BE PUSHING IN OVER NORTHEAST
WYOMING INTO SOUTHWESTERN SOUTH DAKOTA...WHERE READINGS SHOULD
RISE INTO THE 20S. AS SURFACE HIGH MOVES EAST...RETURN FLOW OVER
NORTHEASTERN WYOMING AND FAR WESTERN SOUTH DAKOTA MAY PRODUCE SOME
BREEZY SOUTHERLY WINDS.
WEDNESDAY AND THURSDAY...NORTHWEST FLOW PATTERN CONTINUES AS
UPPER LEVEL RIDGE REMAINS OFF TO THE WEST. TEMPERATURES WILL WARM
A LITTLE EACH DAY...BUT WILL REMAIN BELOW SEASONAL AVERAGES. A
WEAK SHORTWAVE MAY BRING SOME LIGHT SNOW TO PARTS OF THE AREA ON
THURSDAY INTO THURSDAY NIGHT.
EXTENDED...THE PERIOD FROM FRIDAY THROUGH SUNDAY WILL FEATURE AN
UPPER RIDGE OVER THE WESTERN US WITH AN UPPER TROUGH OVER THE
MIDWEST...AND WITH A ROUGHLY N/S ORIENTED SFC BOUNDARY SOMEWHERE
ACROSS WESTERN SOUTH DAKOTA. THE GFS AND ECMWF BOTH ARE SHOWING A
VIGOROUS LOW PRESSURE SYSTEM DROPPING SOUTHWARD ACROSS THE EASTERN
DAKOTAS BUT DIFFER ABOUT 12 HRS ON THE TIMING. THE LOW PRESSURE
SYSTEM WILL RESULT IN COLDER AIR BACKING INTO THE FORECAST AREA
AGAIN FOR THE WEEKEND WITH A SLIGHT CHANCE OF SNOW NEAR AND ALONG
THE SFC BOUNDARY OVER NORTHEASTERN WYOMING AND FAR WESTERN SOUTH
DAKOTA ON SATURDAY AND SATURDAY NIGHT. THE UPPER RIDGE AXIS IS
EXPECTED TO MOVE OVER THE WESTERN PARTS OF THE FORECAST AREA ON
MONDAY...LEADING TO MODERATING TEMPERATURES.
AVIATION
WIDESPREAD MVFR CIGS WITH AREAS OF FLURRIES EXPECTED
THROUGH MID MORNING OVER MUCH OF WESTERN AND CENTRAL SOUTH DAKOTA.
CLEAR SKIES EXPECTED TO CONTINUE OVER NORTHEASTERN WYOMING.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
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