Prognostic Meteorological Discussion
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000 FXUS02 KWBC 231601 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT MON OCT 23 2017 VALID 12Z THU OCT 26 2017 - 12Z MON OCT 30 2017 ...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER/THREATS HIGHLIGHTS... MODELS AND ENSEMBLES SEEM IN REASONABLE OVERALL AGREEMENT THU/FRI AS A WELL ORGANIZED LEAD SYSTEM EJECTS OFF THE ERN SEABOARD INTO THE CANADIAN MARITIMES AND WRN ATLANTIC. THIS OCCURS AS A DYNAMIC UPSTREAM MID-UPPER LEVEL TROUGH DIGS SEWD OVER THE N-CENTRAL US IN RAPIDLY AMPLIFYING MID-UPPER LEVEL FLOW DOWNSTREAM OF A BUILDING NORTH AMERICAN WEST COAST RIDGE. AN ASSOCIATED AND PCPN FOCUSING SURFACE LOW DEVELOPS AND LIFTS ACROSS THE UPPER MIDWEST/GREAT LAKES INTO ERN CANADA DURING THIS PERIOD...WITH ADDITIONAL ACTIVITY ALONG/AHEAD OF A TRAILING COLD FRONT AS POST-FRONTAL COLD HIGH PRESSURE SURGES RAPIDLY DOWN THROUGH THE W-CENTRAL US. GUIDANCE FORECAST SPREAD INCREASES MORE SIGNIFICANTLY OVER THE WEEKEND INTO EARLY NEXT WEEK...EVEN THOUGH THERE IS DECENT AGREEMENT WITH THE IDEA OF SWINGING AN ELONGATED AND WIDESPREAD RAINFALL FOCUSING FRONT ACROSS THE ERN US. POTENTIAL WAVE DEVELOPMENT DETAILS ARE MORE UNCERTAIN...BUT OVERALL DOES SEEM LIKELY GIVEN SUPPORTING MID-UPPER LEVEL TROUGH AMPLITUDE ALOFT. MODELS AND ENSEMBLES ALSO INTRODUCE A THREAT OF A POTENTIAL CARRIBEAN TROPICAL SYSTEM DEVELOPING AND LIFTING UP OFF THE ERN SEABOARD IN ADVANCE OF THE WAVY AND SLOWLY EASTWARD PROGRESSING FRONTAL SYSTEM. THIS WOULD HAVE SOME POTENTIAL TO DRASTICALLY INCREASE AVAILABLE MOISTURE/PCPN INTO THE WRN ATLANTIC AND POSSIBLY THE ERN US. SATELLITE IMAGERY DOES NOT HAVE A CLEAR SIGNAL FOR DEVELOPMENT YET...BUT SOME MODELS INCLUDING ESPECIALLY THE 00 UTC ECMWF/CANADIAN AND UKMET OFFER MORE ORGANIZED AND INCREASINGLY FAST PROPAGATION THAN THE GFS...A WIDE VARIETY OF ENSEMBLE MEMBERS...AND NHC/WPC CONTINUITY. WPC PROGS FOCUS ACTIVITY WITH THE WAVY FRONT AND ARE MORE CONSERVATIVE WITH TROPICAL DEVELOPMENTS PENDING INCREASED SATELLITE/GUIDANCE SIGNALS AND ADDITIONAL NHC COLLABORATION. OVERALL...WPC MEDIUM RANGE SURFACE FRONTS PRESSURES AND 500MB PROGS WERE ACCORDINGLY DERIVED MAINLY FROM THE 00 UTC ECMWF ENSEMBLE MEAN ALONG WITH SMALLER INPUTS FROM THE 06 UTC GFS/GEFS AND 00 UTC ECMWF TO INCORPORATE SOME OF THE ENVELOPE OF GUIDANCE SOLUTIONS. SCHICHTEL $$

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