Prognostic Meteorological Discussion
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000 FXUS02 KWBC 260613 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 212 AM EDT TUE SEP 26 2017 VALID 12Z FRI SEP 29 2017 - 12Z TUE OCT 03 2017 ...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES... PROGRESSIVE PATTERN LATER THIS WEEK WILL ATTEMPT TO RE-ESTABLISH THE WESTERN CONUS TROUGH AND EASTERN RIDGE BY THIS WEEKEND INTO NEXT WEEK. SURFACE COLD FRONT AND SECONDARY FRONT WILL SINK SOUTHEASTWARD FRI-SUN WHILE ANOTHER SYSTEM MOVES THROUGH THE NORTHWEST AND ACROSS THE PLAINS. THE MODELS/ENSEMBLES HAVE STRUGGLED FOR SEVERAL DAYS WITH THE UPSTREAM FLOW OUT OF THE NORTH PACIFIC, AND THE LATEST 12Z ENSEMBLES WERE MUCH THE SAME. DESPITE THE DISAGREEMENT BETWEEN THE 12Z GEFS AND 12Z ECMWF ENSEMBLE AND CANADIAN MEANS, THE 18Z GEFS MEAN CAME INTO BETTER AGREEMENT WITH THE OTHER CENTER MEANS IN THE WEST BY NEXT WEEK SHOWING TROUGHING RELOADING INTO THE WEST COAST LATE MON INTO TUE. BLEND OF THE RECENT 12Z/18Z GFS WITH THE 12Z ECMWF (AND SOME 12Z UKMET) OFFERED A GOOD STARTING POINT FOR THE FIRST FEW DAYS (FRI-SUN). TREND WAS FOR A LITTLE QUICKER PROGRESSION OF THE UPPER TROUGH OUT OF THE NORTHEAST BUT STRONGER RIDGING BEHIND IT THROUGH THE UPPER MIDWEST INTO SOUTH CENTRAL CANADA. THIS WAS AIDED BY THE NOW DUAL UPSTREAM TROUGHING THAT BARRELS INTO THE WEST. DETERMINISTIC MODELS HAVE BEEN WOEFULLY INCONSISTENT BY NEXT SUN/MON, SO A TREND TOWARD THE 18Z GEFS MEAN AND 12Z ECMWF ENSEMBLE MEAN WAS WARRANTED. THE 18Z GFS OFFERED SOME DETAIL TO THE LAST DAYS OF THE FORECAST AS THE ECMWF SEEMED TOO DEEP WITH ITS SECOND UPPER LOW CENTERED OFF SW OREGON BY NEXT TUE PER THE ENSEMBLE SPAGHETTI. ...WEATHER HIGHLIGHTS... PRECIPITATION WILL BE FAVORED ALONG AND AHEAD OF THE FRONT IN THE SOUTHEAST, PRIMARILY IN FLORIDA, BUT ALSO IN THE NORTHEAST AS THE UPPER LOW AND SECONDARY FRONT DEPART. THE PAC NW WILL SEE BOUTS OF RAIN AND MOUNTAIN SNOW WITH THE FIRST FRONTAL AND THEN THE UPPER TROUGH PASSAGE FRI-SUN FOLLOWED BY THE NEXT SYSTEM MON-TUE. ADDITIONAL RAINFALL IS LIKELY OVER WESTERN TEXAS BACK THROUGH NM/CO AROUND THE BACKSIDE OF THE UPPER HIGH EARLY IN THE PERIOD. TEMPERATURES WILL SETTLE BACK TO WITHIN THE MORE TYPICAL RANGE OF LATE SEPT/EARLY OCT -- FEW, IF ANY, RECORD HIGHS/LOWS ARE EXPECTED. FRACASSO $$

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