EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 226 AM EDT WED SEP 30 2015 VALID 12Z SAT OCT 03 2015 - 12Z WED OCT 07 2015 ...JOAQUIN GAINING HURRICANE STRENGTH TO THREATEN THE ERN US/WRN ATLANTIC... ...OVERVIEW... THE MEDIUM RANGE FCST REMAINS MARKED BY CONSIDERABLE MODEL/ENSEMBLE SPREAD FOR MOST OF THE PERIOD. THIS IS WITHIN A PATTERN THAT SHOULD BE RATHER BLOCKY WITH MULTIPLE CLOSED FEATURES OVER NOAM AND ERN PAC/WRN ATLC EARLY-MID PERIOD WITH AN EVENTUAL TRANSITION TO A LOWER AMPLITUDE/MORE PROGRESSIVE REGIME WHICH ALSO TENDS TO HAVE LOWER PREDICTABILITY. THE GUIDANCE SPREAD IS ESPECIALLY PROBLEMATIC GIVEN THE LIKELY PRESENCE OF JOAQUIN OFF THE EAST COAST AND SIGNIFICANT DIFFS IN SENSIBLE WEATHER EFFECTS OVER PARTS OF THE WEST. CONSULT LATEST NHC PRODUCTS FOR FURTHER INFORMATION REGARDING JOAQUIN. ...GUIDANCE EVALUATION AND SENSIBLE WEATHER HIGHLIGHTS... THERE REMAINS A LACK OF CONFIDENCE IN ANY PARTICULAR MODEL OVER THE FULL FCST DOMAIN LEADS TO A STARTING BLEND INCORPORATING THE 18Z GEFS/12Z ECMWF MEANS WITH SOME SIGNIFICANT MANUAL ADJUSTMENT TO FIT THE LATEST NHC FORECAST FOR JOAQUIN AS WELL AS INCORPORATING GUIDANCE TRENDS AND UNCERTAINTY. OVER THE EAST...THERE HAS BEEN A SIGNIFICANT RECENT TREND TOWARD GREATER EMPHASIS OF A SERN US TROUGH/UPR LOW VERSUS ANOTHER UPR LOW OVER ERN CANADA OR SOMEWHERE IN-BETWEEN. EVEN WITH THIS TREND THERE IS STILL WIDE DIVERGENCE. IN GENERAL THE SYNOPTIC PATTERN APPEARS VERY FAVORABLE FOR HVY RNFL POTENTIAL ALONG AND INLAND FROM THE CNTRL-NRN EAST COAST. THE IMPORTANT UNRESOLVED DETAILS OF FLOW ALOFT AND INTERACTION WITH JOAQUIN ULTIMATELY WILL DETERMINE LOCATION AND TIMING/INTENSITY/DURATION OF HEAVIEST RNFL. OVER THE WEST THE MOST SIGNIFICANT FCST PROBLEM IS THE EVOLUTION OF ENERGY INITIALLY COMING INTO WRN BC AND THEN AMPLIFYING INTO THE WEST. RECENT ECMWF AND CMC RUNS HAVE BEEN CONSISTENT SHOWING A RATHER VIGOROUS COMPACT CLOSED LOW DROPPING SWD ALONG OR JUST INLAND FROM THE WEST COAST AND TRACKING INTO/NEAR THE GRTBASIN BEFORE OPENING UP AS UPSTREAM FLOW FLATTENS. ECMWF/CMC ENSEMBLES CONTAIN THEIR RESPECTIVE OPERATIONAL SOLNS WHILE THE RESULTING MEANS ARE WEAKER/EWD BUT STILL SHOW A STRONGER/MORE SEPARATED SYSTEM ALOFT THAN A MAJORITY OF RECENT GFS/GEFS RUNS...ALBEIT WITH THE 00 UTC GFS TRENDING DEEPER AND THE 00 UTC ECMWF SLIGHTLY WEAKER. THE TENDENCY FOR AMPLITUDE/BLOCKINESS OF SURROUNDING FLOW SEEMS TO FAVOR ADJUSTING THE INITIAL BLEND SOMEWHAT MORE TOWARD THE ECMWF MEAN AT LEAST. COMBINATION OF THIS FEATURE AND LEADING SHRTWV ENERGY PROVIDE THE BEST GUIDANCE AGREEMENT FOR PCPN OVER THE ROCKIES/PLAINS. RAUSCH/SCHICHTEL