EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 256 AM EDT SUN SEP 27 2015 VALID 12Z WED SEP 30 2015 - 12Z SUN OCT 04 2015 ...HEAVY SERN/ERN US RAINFALL POTENTIAL... ...GUIDANCE/UNCERTAINY ASSESSMENT... DETERMINISTIC MODEL RUN-RUN CONTINUITY IS LESS THAN STELLAR WITH SYSTEM INTERACTIONS AND EMBEDDED SYSTEM AMPLITUDE/TIMINGS MIDWEEK...AND RAPIDLY DEGRADES LATER WEEK AND NEXT WEEKEND. WITHOUT A CLEAR TREND/PREFERENCE FOR A PARTICULAR SCENARIO IN THIS HIGHLY UNCERTAIN LONGER TERM PATTERN...AGAIN INSTEAD PREFER AN ENSEMBLE MEAN FORECAST APPROACH. ACCORDINGLY...THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A BLEND OF SOMEWHAT MORE CONSISTENT AND COMPATABLE GUIDANCE FROM THE 18 UTC GEFS MEAN AND 12 UTC ECMWF ENSEMBLE MEAN. ...SENSIBLE WEATHER HIGHLIGHTS/THREATS... THE NATIONAL HURRICANE CENTER CONTINUES TO MONITOR DEVELOPMENT UP FROM THE GULF OF MEXICO OVER THE NEXT COUPLE OF DAYS. DEEP POOLING MOISTURE COULD FUEL HEAVY RAINFALL OVER THE SERN US THROUGH MIDWEEK. ACTIVITY COULD INTERSECT WITH A DRAPED FRONT OVERTOP AND ALSO SPREAD NNEWD UP THE EAST COAST INTO AND ON THE ERN PERIPHERY OF DAMNED/COOLING ERN US HIGH PRESSURE...WITH THE TRAILING FRONT PROVIDING A SLOW TO ERODE FOCUS FOR LINGERING PCPN ALL WEEK. MEANWHILE...MID-UPPER LEVEL TROUGH ENERGY WILL WORK INLAND ACROSS THE NWRN US WED/THU WITH MODEST MOISTURE BUT DYNAMIC SUPPORT. THIS SHOULD FAVOR A SWATH OF MAINLY TERRAIN ENHANCED PCPN ACROSS THE NWRN US AND N-CENTRAL ROCKIES. ENERGY REACHING THE N-CENTRAL US SHOULD COMBINE WITH AMBIENT MOISTURE THERE TO FUEL SOME HEAVIER LOCAL CONVECTIVE DOWNPOURS BEFORE SHEARING INTO THE E-CENTRAL STATES IN SOME FORM. ADDITIONAL MID-UPPER LEVEL TROUGH ENERGY MAY ALSO SPREAD SOME SHOWERS INLAND INTO THE NWRN STATES NEXT WEEKEND. SCHICHTEL