PROGNOSTIC METEOROLOGICAL DISCUSSION

 
 FXUS01 KWBC 240838
 PMDSPD
  
 SHORT RANGE FORECAST DISCUSSION
 NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
 338 AM EST TUE NOV 24 2009
  
 VALID 12Z TUE NOV 24 2009 - 00Z THU NOV 26 2009
  
 THE UPPER-LEVEL PATTERN ACROSS THE NATION WILL CONSIST OF AN
 AMPLIFYING TROUGH ACROSS THE CENTER OF THE COUNTRY WITH A PAIR OF
 RIDGES POSITIONED ON EITHER SIDE. THE STRONGER DOME OF HIGH
 PRESSURE WILL EXIST OVER THE INTERMOUNTAIN WEST WHICH APPEARS TO
 BE A MAINSTAY FEATURE INTO THANKSGIVING MORNING. MEANWHILE...THE
 MEAN TROUGH ACROSS THE CENTRAL U.S. WILL BE A HIGHLY PROGRESSIVE
 FEATURE WHICH WILL EVENTUALLY ERODE THE RIDGE ALONG THE EAST COAST
 AND PUSH IT OUT TO SEA.
 
 THE WEATHER SYSTEM CURRENTLY MOVING THROUGH THE CENTRAL PLAINS IS
 BRINGING WIDESPREAD RAIN SHOWERS TO THE MID-SECTIONS OF THE
 COUNTRY...BUT WITH NO ACCOMPANYING WINTRY WEATHER. WHILE THIS
 FRONTAL SYSTEM IS BRINGING A CHANGE IN AIR MASS...THE PACIFIC
 ORIGIN OF THIS DISTURBANCE IS PRIMARILY BRINGING DRIER AIR WITH
 ONLY A LIMITED DROP IN TEMPERATURES. HOWEVER...A SECOND SYSTEM
 WHICH WILL SPILL INTO THE NORTHERN TIER STATES BY LATE TUESDAY
 NIGHT IS FORECAST TO BRING AN ADDITIONAL SHOT OF COOLER AIR...THIS
 TIME FROM A CANADIAN AIR MASS. CONSEQUENTLY...AS THE SWATH OF
 PRECIPITATION SPREADS TO THE NORTH AND EAST...EXPECT A CHANGEOVER
 TO LIGHT TO MODERATE SNOW ACROSS THE NORTHERN PLAINS AND UPPER
 MISSISSIPPI VALLEY BY EARLY WEDNESDAY MORNING. IN THE WAKE OF THIS
 WEATHER SYSTEM...THE COLDER AIR WILL MAKE ITS PRESENCE FELT AS
 LOWS IN THE TEENS WILL BE COMMONPLACE ON WEDNESDAY NIGHT ACROSS
 MUCH OF THE NORTHERN PLAINS AND DOWN INTO AREAS OF THE CENTRAL
 PLAINS.
 
 ALTHOUGH THE MAIN STORM TRACK HAS SHIFTED NORTHWARD INTO WESTERN
 CANADA...THIS WILL NOT RULE OUT SCATTERED RAIN SHOWERS ACCOMPANIED
 BY HIGHER ELEVATIONS SNOW ACROSS PORTIONS OF WASHINGTON STATE
 DURING THE NEXT COUPLE OF DAYS. THE ACTIVITY SHOULD PICK UP
 INTENSITY QUITE A BIT BY TUESDAY NIGHT AS A STRONG DISTURBANCE
 SLAMS INTO WESTERN CANADA SPREADING MODERATE TO HEAVY RAINFALL
 ACROSS BRITISH COLUMBIA AND DOWN INTO PORTIONS OF NORTHWESTERN
 WASHINGTON. BY WEDNESDAY EVENING...THE AREA OF PRECIPITATION IS
 FORECAST TO DROP SOUTHWARD AND BEGIN IMPACTING PORTIONS OF
 NORTHERN OREGON. FURTHER INLAND...MUCH OF THE INTERMOUNTAIN WEST
 SHOULD BE SAFE FROM THIS AREA OF INCLEMENT WEATHER AS A RESULT OF
 A STRONG AREA OF SURFACE HIGH PRESSURE. A CONSEQUENCE OF THIS
 HOWEVER WILL BE ENHANCED OFFSHORE FLOW WHICH WILL INCREASE THE
 WILDFIRE DANGER ACROSS SOUTHERN CALIFORNIA THROUGH THURSDAY
 MORNING.
 
 ELSEWHERE...A STALLED FRONTAL BOUNDARY WILL KEEP THE WEATHER
 UNSETTLED ACROSS THE SUNSHINE STATE THROUGH THANKSGIVING MORNING.
 SCATTERED SHOWERS AND THUNDERSTORMS...WITH ISOLATED HEAVIER STORMS
 ARE ALL POSSIBLE GIVEN THE UNSTABLE AIR MASS IN PLACE. 
 
 
 RUBIN-OSTER
  
 
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