793
FXUS01 KWBC 240856
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
456 AM EDT THU SEP 24 2009
VALID 12Z THU SEP 24 2009 - 00Z SAT SEP 26 2009
THE UNSEASONABLY STRONG UPPER LOW THAT FORMED OVER THE CENTRAL
HIGH PLAINS TWO DAYS AGO WILL MOVE VERY LITTLE THURSDAY AND INTO
FRIDAY AS IT REMAINS CUTOFF FROM THE MAIN BAND OF WESTERLIES
ACROSS CANADA AND WILL CONTINUE TO SPIN OVER WESTERN KANSAS AND
WESTERN NEBRASKA. SLIGHT PROGRESSION EASTWARD IS POSSIBLE LATE
FRIDAY INTO EARLY SATURDAY AS A SERIES OF HEIGHT FALLS MOVING INTO
WESTERN AND CENTRAL CANADA BEGIN TO AFFECT IT. WITH LITTLE
MOVEMENT OF THIS FEATURE EXPECTED OVER THE NEXT TWO DAYS...THE
ASSOCIATED WET WEATHER IN THE VICINITY OF THE UPPER LOW WILL
PERSIST OVER THE NEXT FEW DAYS OVER PORTIONS OF THE PLAINS STATES.
WITH LITTLE MOVEMENT TO THIS CLOSED LOW THERE WILL ALSO BE LITTLE
MOVEMENT TO THE PRIMARY AXIS OF HIGH PW AIR TO THE EAST OF THIS
SYSTEM STRETCHING FROM THE WESTERN TO CENTRAL GULF
COAST...NORTHWARD THROUGH THE MISSISSIPPI VALLEY AND OHIO VALLEY.
ADDITIONAL MODERATE TO HEAVY RAINFALL AMOUNTS POSSIBLE OVER THE
NEXT TWO DAYS ACROSS THESE REGIONS..WITH A EASTWARD SHIFT TO THE
AXIS OF HEAVIEST RAINS BY THE END OF THIS FORECAST PERIOD INTO THE
UPPER OHIO VALLEY AND THE APPALACHIANS/MID ATLANTIC AS THE ABOVE
MENTIONED INCREASED PROGRESSION TO THE UPPER LOW OCCURS.
WHILE THE LARGE SCALE FEATURES CHANGE LITTLE OVER THE LOWER
48..THE UPPER FLOW WILL REMAIN VERY PROGRESSIVE ACROSS CANADA AN
INITIAL AREA OF HEIGHT FALLS IN THIS PROGRESSIVE FLOW WILL
CONTINUE TO PUSH A WELL DEFINED COLD FRONT SOUTHWARD THROUGH THE
NORTHEAST THURSDAY INTO FRIDAY...WITH A COOL FALL AIRMASS BECOMING
CENTERED OVER NORTHERN NEW ENGLAND BY THE BEGINNING OF THE
WEEKEND.
AREAS TO THE WEST OF ROCKIES WILL REMAIN DRY OVER THE NEXT FEW
DAYS AS MID TO UPPER LEVEL RIDGING IN THE MEAN CONTINUES TO
DOMINATE. A WEAK NORTHEASTERN PACIFIC SYSTEM WILL TRY TO PUSH
INTO THIS MEAN RIDGE POSITION THURSDAY BUT IS EXPECTED TO BECOME
SHEARED AND WEAKEN WITH NO ASSOCIATED PRECIPITATION. IT WILL BRING
SOME COOLER AIR TO THE PACIFIC NORTHWEST WHERE TEMPERATURES HAVE
BEEN ABOVE NORMAL RECENTLY. NO RELIEF FROM THE ABOVE NORMAL
TEMPERATURES FARTHER TO THE SOUTH ACROSS MOST OF CALIFORNIA AND
INTO THE DESERT SOUTHWEST. IN ADDITION TO THE ABOVE NORMAL
TEMPERATURES...THE FIRE DANGER WILL REMAIN HIGH ACROSS PORTIONS OF
SOUTHERN CALIFORNIA WHERE GUSTY OFFSHORE WINDS AND LOW HUMIDITIES
WILL PERSIST.
ORAVEC
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