EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 AM EDT THU OCT 16 2014 VALID 12Z SUN OCT 19 2014 - 12Z THU OCT 23 2014 ...PATTERN OVERVIEW AND GUIDANCE EVALUATION... THERE REMAINS GOOD AGREEMENT ON THE IDEA OF AN AMPLIFIED PATTERN WITH A TENDENCY TOWARD SOME SEPARATION OF FLOW WITHIN SEPARATE TROUGHS NEAR THE EAST COAST AND PROGRESSING INTO WRN NOAM. THIS SEPARATION IS IN RESPONSE TO THE LATE-PERIOD EVOLUTION TOWARD THE MAIN BAND OF WESTERLIES BECOMING ESTABLISHED FROM THE ERN PAC ACROSS THE NWRN CONUS AND ENEWD ACROSS CANADA... DOWNSTREAM FROM A FAIRLY DEEP NERN PAC TROUGH. INTO EARLY DAY 5 TUE GUIDANCE CLUSTERING IS SUFFICIENTLY GOOD TO RECOMMEND A GENERAL MODEL/ENSEMBLE BLEND AS THE STARTING POINT FOR THE FCST. HOWEVER FROM LATE TUE ONWARD RECENT TRENDS OVER BOTH THE EAST AND WEST SUGGEST A BLEND OF THE 00Z ECMWF MEAN AND PAST TWO OPERATIONAL ECMWF RUNS AS THE BEST OVERALL SOLN ACROSS THE CONUS. AFTER A COUPLE DAYS OF CONSIDERABLE SPREAD... GUIDANCE HAS MADE CONSIDERABLE PROGRESS TOWARD CONVERGING ON A COMMON SOLN OVER THE ERN HALF OF THE CONUS/WRN ATLC. LATEST CONSENSUS HAS AMPLIFYING NRN TIER CONUS/SRN CANADA ENERGY SUPPORTING A SFC WAVE THAT REACHES THE WRN/UPR GRTLKS BY EARLY DAY 4 MON FOLLOWED BY A TRANSFER OF ENERGY OFF THE COAST AROUND DAY 5 TUE. THIS CLUSTER IS CLOSE TO THE PAST TWO ECMWF RUNS VERSUS FARTHER N OR S TRACKS AS DEPICTED IN RUNS BEFORE THOSE. THE GFS HAS TAKEN LONGER TO LATCH ONTO A WELL DEFINED SFC WAVE IN THE SUN-TUE TIME FRAME. BY DAY 6 WED THERE IS A NOTICEABLE TREND IN THE ENSEMBLE GUIDANCE TOWARD GREATER SEPARATION OF FLOW ALOFT WITH THE PAST TWO ECMWF MEANS NOW MOST SIMILAR TO RECENT GFS/ECMWF RUNS THAT HAVE BEEN CLOSING OFF A LOW ALOFT. LATEST GEFS MEANS ARE SHOWING SEPARATION ALOFT BUT OVERALL APPEAR TOO WEAK WITH THEIR MID LVL/SFC REFLECTIONS GIVEN THE GFS/ECMWF/ECMWF MEAN CLUSTER. DUE TO UPSTREAM ISSUES ONLY THE ECMWF MEAN AND PAST TWO ECMWF RUNS ARE INCLUDED IN THE FCST BLEND BUT THE 00Z GFS COMPARES ACCEPTABLY IN PRINCIPLE FOR THE UPR LOW AND WRN ATLC SFC SYSTEM. THE 06Z GFS BECOMES A LITTLE MORE PROGRESSIVE BY DAY 7 THU. FARTHER WWD... THE 06Z GEFS MEAN HAS ADJUSTED A LITTLE SLOWER THAN OTHER SOLNS WITH THE TROUGH NEAR THE WEST COAST BY DAY 5 TUE. FROM THIS POINT ONWARD REMAINING PIECES OF GUIDANCE SHOW INCREASING DIVERGENCE IN SPITE OF FAIRLY SIMILAR FLOW EXPECTED IMMEDIATELY UPSTREAM. THE STRENGTH OF THE PLAINS INTO MS VLY RIDGE AND SLOWING/MORE CLOSED EVOLUTION NEAR THE EAST COAST SEEM TO RECOMMEND LEANING AWAY FROM THE 00Z GFS/CMC WHICH ARE FASTEST TO BRING WRN HGT FALLS INTO THE PLAINS. TRENDS AS WELL AS THE EVOLUTION OF PRECEDING ENERGY REACHING THE WEST COAST SEEM TO FAVOR THE ENSEMBLE MEANS THAT PULL OFF SOME ENERGY INTO THE SWRN CONUS/EXTREME NWRN MEXICO WHILE NRN STREAM ENERGY CONTINUES NEWD. TIMING/EVOLUTION OF THE SRN BUNDLE OF ENERGY MAY HAVE A SIGNIFICANT INFLUENCE ON SENSIBLE WEATHER OVER/NEAR THE SRN ROCKIES/HIGH PLAINS. WILL CONTINUE TO MONITOR SFC LOW PRESSURE THAT MOST GUIDANCE HAS BEEN SHOWING OVER THE SWRN GULF OF MEXICO IN RECENT DAYS. OVER THE PAST COUPLE DAYS INDIVIDUAL SOLNS ON THE NRN/ERN SIDE OF THE TRACK ENVELOPE IN A PARTICULAR CYCLE HAVE TENDED TO REVERT BACK TOWARD THE MAJORITY CLUSTER IN FOLLOWING RUNS... SO THE 06Z GFS/00Z CMC APPEAR TO BE THE LESS PROBABLE SOLNS AT THIS TIME. ...SENSIBLE WEATHER HIGHLIGHTS... THE LARGE SCALE PATTERN CONTINUES TO OFFER THE BEST CONFIDENCE FOR LOCALLY HVY RNFL ALONG THE NRN HALF OF THE WEST COAST WITH HIGHEST TOTALS FOCUSED NEAR VANCOUVER ISLAND. THERE SHOULD BE TWO PRIMARY EVENTS... ONE AT THE START OF THE WEEK AND A SECOND WITH LESS SWD EXTENT AROUND THE MIDDLE OF THE WEEK. NEXT HIGHEST ON THE CONFIDENCE SCALE FOR ENHANCED RNFL POTENTIAL WOULD BE PARTS OF NEW ENGLAND IN THE LATTER HALF OF THE PERIOD IN ASSOC WITH THE PSBL EAST COAST CLOSED LOW ALOFT AND WRN ATLC SFC SYSTEM. MORE UNCERTAINTY EXISTS FROM THE SRN ROCKIES/HIGH PLAINS SEWD ALONG THE RIO GRANDE VLY AS WELL AS OVER THE SRN FL PENINSULA. CURRENT PREFS ALOFT FOR A SLOWER/MORE SEPARATED SOLN LATE IN THE FCST WOULD FAVOR HIGHER RNFL POTENTIAL OVER THE FORMER AREA WHILE THUS FAR THERE HAS BEEN A FAIR AMOUNT OF SPREAD REGARDING HOW MUCH OF THE AMPLE DEEP MSTR OVER THE CNTRL-SRN GULF MSTR REACHES THE LATTER. AREAS EAST OF THE MS RIVER SHOULD BE ON THE CHILLY SIDE WITH THE CORE OF GREATEST NEGATIVE ANOMALIES FOR HIGHS LIKELY TO EXTEND FROM THE GRTLKS/OH VLY INTO THE MID ATLC/SRN NEW ENGLAND WITH ONE OR MORE DAYS NEAR OR GREATER THAN 10F BELOW NORMAL. ON THE OTHER HAND AREAS FROM THE NRN ROCKIES ACROSS THE NRN PLAINS MAY SEE MULTIPLE DAYS WITH HIGHS OF 10-20F ABOVE NORMAL... WHICH COULD APPROACH OR REACH DAILY RECORD VALUES AT SOME LOCATIONS. RAUSCH