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000 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 $$
