EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1158 AM EDT WED SEP 30 2015 VALID 12Z SAT OCT 03 2015 - 12Z WED OCT 07 2015 ...HURCN JOAQUIN REMAINS A THREAT TO THE ERN US/WRN ATLANTIC... ...OVERVIEW... LATEST GUIDANCE MAINTAINS THE GENERAL THEME OF A TRANSITION FROM A BLOCKY PATTERN CONTAINING MULTIPLE CLOSED FEATURES TOWARD A LOWER AMPLITUDE AND PROGRESSIVE REGIME. MODEL/ENSEMBLE SPREAD REMAINS GREATER THAN DESIRED LEADING TO SIGNIFICANT QUESTION MARKS FOR SENSIBLE WEATHER IMPACTS OVER SOME AREAS... ESPECIALLY NEAR THE EAST COAST WHERE MINOR DIFFS IN THE TRACK OF HURCN JOAQUIN WILL MAKE A BIG DIFFERENCE. CONSULT LATEST NHC PRODUCTS FOR FURTHER INFORMATION REGARDING JOAQUIN. ...GUIDANCE EVALUATION/PREFERENCES... THE UPDATED FCST BLEND STARTS WITH A 70/30 WEIGHTING OF THE 00Z ECMWF MEAN/06Z GEFS MEAN BASED ON PREFS FOR ERN PAC INTO CNTRL CONUS FLOW LEANING MORE TOWARD A MAJORITY ECMWF-BASED CLUSTER AND SOME DEGREE OF COMPROMISE OVER THE EAST WITH ALLOWANCE FOR MANUAL ADJUSTMENT TO INCORPORATE THE OFFICIAL FCST FOR JOAQUIN. OVER THE WEST... BY THE START OF THE FCST PERIOD THE TRENDS OVER THE PAST 24 HRS HAVE BEEN IN THE DIRECTION OF ECMWF/CMC WITH THE UPR LOW DROPPING INTO THE NORTHWEST AS OF DAY 3 SAT SO CLUSTERING IS NOW BETTER THAN IT WAS PREVIOUSLY. HOWEVER SOLNS DIVERGE FAIRLY RAPIDLY IN RESPONSE TO HOW QUICKLY UPSTREAM PAC ENERGY CUTS INTO THE UPR RIDGE OFF THE WEST COAST. AT THIS TIME THERE IS A DECENT MAJORITY CLUSTER AMONG MDLS/ENSMEANS TOWARD THE RIDGE BEING ERODED MORE SLOWLY THAN DEPICTED IN RECENT GFS/GEFS MEANS THUS ALLOWING FOR THE WRN CONUS UPR LOW TO TRACK FARTHER SWD. AS THE LARGE SCALE PATTERN FLATTENS... THE WRN TROUGH SHOULD PROGRESS INTO THE PLAINS WITH A LEADING WAVY SFC FRONT. THIS IDEA SEEMS TO LEAD FAIRLY WELL INTO TELECONNECTION-FAVORED FLOW AT AND BEYOND THE END OF THE FCST PERIOD... A WRN RIDGE AND ERN TROUGH ALOFT IN RESPONSE TO DEVELOPMENT OF A CORE OF NEG HGT ANOMALIES BTWN AK/HI BY THE D+8 TIME FRAME. THE FCST OVER THE EAST REMAINS PROBLEMATIC ESPECIALLY CONSIDERING THE SPREAD THAT ALREADY EXISTS AT THE SHORT RANGE... NOT ONLY WITH HURCN JOAQUIN BUT WITH AN ERN CANADA UPR TROUGH WHOSE POSN AS OF EARLY DAY 3 SAT MAY BE ANYWHERE FROM STILL W OF NEW ENGLAND TO EJECTING PAST THE CANADIAN MARITIMES. 06Z/00Z GFS RUNS ARE THE FAST EXTREME WITH THIS NRN TROUGH AS EVEN THE 06Z GEFS MEAN IS CLOSER TO THE 00Z ECMWF. WITH THE UPR LOW INITIALLY OVER THE SOUTHEAST THE ECMWF CONTINUES TO BECOME A PRONOUNCED SRN EXTREME BY SUN-MON... BRIEFLY BECOMING AN OUTLIER RELATIVE TO ITS FULL ENSEMBLE ENVELOPE. AT ITS MOST EXTREME THE 00Z ECMWF SHOWS SOME MINUS 5-6 STDEVS FOR MID LVL HGTS. PARTICULARLY INTERESTING IS THE APPARENT LACK OF CONNECTION BTWN WRN CONUS FLOW DETAILS AND HOW QUICKLY THE SERN UPR LOW LIFTS NWD. THIS IS MOST SIMPLY ILLUSTRATED BY THE ECMWF/CMC MEANS WITH BOTH SIMILAR OVER THE WEST BUT THE CMC MEAN LIFTING THE ERN LOW MUCH MORE QUICKLY NWD. MULTI-DAY TRENDS LEAN SLOWER TO FAVOR A SOLN CLOSER TO THE ECMWF MEAN BUT WITH RESERVATIONS ON THE EXTREME OPERATIONAL ECMWF. CONSULT LATEST NATIONAL HURRICANE CENTER PRODUCTS FOR FURTHER INFO REGARDING HURCN JOAQUIN INTO DAY 5 FRI. CURRENTLY EXPECT AN EXTRATROPICAL TRANSITION WITH A TRACK NEAR THE NEW ENGLAND COAST AND INTO THE CANADIAN MARITIMES BY DAYS 6-7 TUE-WED. ...SENSIBLE WEATHER HIGHLIGHTS... LOCATIONS ALONG AND INLAND FROM THE EAST COAST SHOULD CONTINUE TO MONITOR FCSTS FOR HURCN JOAQUIN IN THE COMING DAYS. IMPORTANT DETAILS REMAIN YET TO BE RESOLVED BUT POTENTIAL REMAINS FAVORABLE IN GENERAL FOR SOME AREAS TO SEE A COMBINATION OF STRONG WINDS AND HVY RNFL. MEANWHILE EXPECT AREAS OF PCPN OVER THE WRN-CNTRL STATES IN ASSOC WITH A LEADING SHRTWV EJECTING OUT OF THE ROCKIES DURING THE WEEKEND AND TRAILING TROUGH/EMBEDDED UPR LOW DIGGING INTO THE WEST AND THEN HEADING INTO THE PLAINS. AHEAD OF THIS LATTER TROUGH... WILL HAVE TO WATCH A PSBL FEED OF ERN PAC MSTR/ENERGY ALOFT EXTENDING NEWD ACROSS MEXICO AND INTO THE PLAINS. CURRENT SIGNALS ARE NOT AS PRONOUNCED AS IN SOME RECENT EVENTS BUT THERE HAS BEEN AN ISOLD MODEL RUN OR TWO INDICATING A PSBL ENHANCEMENT TO RNFL. FOR TEMPS... GREATEST BELOW NORMAL ANOMALIES FOR HIGHS SHOULD BE OVER CNTRL-ERN AREAS DURING THE WEEKEND. HIGHS SHOULD BE WITHIN 10F OF NORMAL OVER MOST OF THE LOWER 48 BY THE MIDDLE OF NEXT WEEK. UNSETTLED WEATHER OVER THE WEST AND EAST SHOULD KEEP MIN TEMPS WARMER AND THE FLATTENING OF THE PATTERN ALOFT SHOULD TEND TO FAVOR NEAR TO ABOVE NORMAL MINS OVER MOST OF THE COUNTRY BY LATE IN THE PERIOD. RAUSCH