PROGNOSTIC METEOROLOGICAL DISCUSSION

 
 FXUS02 KWBC 231810
 PMDEPD
  
 EXTENDED FORECAST DISCUSSION
 NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
 109 PM EST MON NOV 23 2009
  
 VALID 12Z THU NOV 26 2009 - 12Z MON NOV 30 2009
  
 TELECONNECTIONS WITH POSITIVE ANOMALIES MOST CONCENTRATED NEAR
 NUNAVUT AND THE YUKON FAVOR PROGRESSIVE CLOSED CYCLONES UNDER
 THEIR BASE NEAR THE WESTERN US/CANADIAN BORDER AND SOUTHEAST
 CANADA.  THIS PATTERN SHOULD BRING BOUTS OF HEAVY PRECIPITATION TO
 THE NORTHEAST AND NORTHWEST...THOUGH LATE THIS WEEKEND INTO EARLY
 NEXT WEEK THE GULF OF MEXICO COULD OPEN UP ALLOWING FOR HEAVY
 RAINFALL ALONG THE WESTERN AND CENTRAL GULF COAST.  THE GUIDANCE
 GENERALLY AGREES ON THIS SCENARIO.  
 
 THERE ARE SOME DETAIL DIFFERENCES IN THE GUIDANCE...PARTICULARLY
 ACROSS THE NORTHEAST AND WEST LATE THIS WEEK...AND THE WEST AND
 MIDWEST FROM THIS WEEKEND INTO EARLY NEXT WEEK.  ACROSS THE UPPER
 MISSISSIPPI VALLEY/UPPER MIDWEST/GREAT LAKES THIS WEEKEND INTO
 EARLY NEXT WEEK...THE 00Z MULTI-MODEL ENSEMBLE MEMBERS SUPPORT A
 MORE 00Z CANADIAN IDEA WITH A POSSIBLY CLOSED CYCLONE SLOWLY
 CROSSING INTO THE GREAT LAKES.  THE ECMWF HAS BEEN VACILLATING
 BACK AND FORTH BETWEEN A STRONGER/WEAKER SYSTEM IN THIS REGION
 OVER ITS PAST COUPLE DAYS OF RUNS...THOUGH ITS 36 HOUR TREND IS
 TOWARDS THE 00Z CANADIAN IDEA.  A FEW OF THE 00Z ECMWF/CANADIAN
 ENSEMBLE MEMBERS ADVERTISE A DEEP CYCLONE WHICH WOULD CLOSE OFF AS
 FAR SOUTHWEST AS KANSAS BY NEXT MONDAY MORNING.  BECAUSE OF THE
 UNCERTAINTY WITH THE DEEP CYCLONE PLACEMENT EAST OF THE
 ROCKIES...THE STRENGTH OF THE TROUGHING /AND THE POSSIBILITY OF A
 CLOSED CYCLONE/ MOVING THROUGH THE ROCKIES IS ALSO
 UNCLEAR...ALTHOUGH THERE IS A STRONG ENOUGH SIGNAL IN THE GUIDANCE
 TO WORRY ABOUT A SIGNIFICANT FOEHN/SANTA ANA-TYPE EVENT IN
 CALIFORNIA THIS WEEKEND. 
 
 WITH ALL THIS IN MIND...USED A COMPROMISE OF THE 06Z GFS/00Z ECMWF
 THROUGH FRIDAY BEFORE USING A 40/40/20 BLEND OF THE 06Z GFS OR ITS
 ENSEMBLE MEAN/00Z ECMWF/00Z CANADIAN TO HELP RESOLVE DIFFERENCES
 IN ALL REGIONS.  MODIFICATIONS WERE INITIALLY MADE PER 00Z
 MULTI-MODEL ENSEMBLE LOW CLUSTERING...ESPECIALLY ACROSS THE DEEP
 SOUTH AND GREAT LAKES...AND WERE THEN FURTHER REFINED USING THE
 12Z DETERMINISTIC GUIDANCE.  THIS SOLUTION MAINTAINED GOOD
 CONTINUITY.
 
 ROTH