EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1119 AM EDT THU OCT 23 2014 VALID 12Z SUN OCT 26 2014 - 12Z THU OCT 30 2014 ...GUIDANCE EVALUATION... THE 00Z-06Z GFS HAVE ONE OF THE LESS LIKELY PACIFIC/WRN NOAM SOLNS ALOFT RESULTING FROM A NORTHERN STREAM TROUGH ROTATING AROUND THE BASE OF THE PERSISTENT CLOSED LOW NEAR 63N 180W SUNDAY 26 OCT. AS A RESULT OF THE AMPLIFIED WAVE...THE 00-06Z GFS PRODUCES A CLOSED LOW NEAR 49N 151 00Z WED 29 OCT...WITH THE ECMWF/CANADIAN GLOBAL MODELS FURTHER NORTHEAST. THE MULTI-DAY ENSEMBLE MEANS ARE SUGGESTING A CORE OF POSITIVE HGT ANOMALIES TO THE SW OF ALASKA AND ALEUTIANS. TELECONNECTIONS RELATIVE TO THIS FEATURE FAVOR A POSITIVELY TILTED TROUGH NEARING THE PAC NW COAST. THE 00Z/CANADIAN AND ECMWF MEANS TRANSITION TOWARDS THIS PATTERN TO PROVIDE A LITTLE MORE CONFIDENCE IN THESE MEANS VERSUS THE 00-06Z GFS AND 00-06Z GEFS MEAN. THE CLOSED LOW DEVELOPED BY THE 00-06Z GFS RESULTS IN SLOWER FORWARD MOTION AND TROUGH POSITION FURTHER WEST. PREFER TO WAIT UNTIL OTHER MODEL/ENSEMBLES MOVE TOWARDS THIS POSITION BEFORE GIVING MUCH CREDENCE TO THE GFS FCST. THE FINAL FCSTS BLENDED THE 00Z ECMWF ENSEMBLE MEAN WITH THE CANADIAN ENSEMBLE MEAN TIMING. THE 00Z CANADIAN GLOBAL SFC LOW PRESSURE MATCHED THE 00Z ECMWF ENSEMBLE MEAN OFF THE PACIFIC NORTHWEST...BUT WAS OUT OF PHASE WITH OTHER FORECASTS UPSTREAM IN THE PACIFIC AND DOWNSTREAM IN THE US...SO THE 00Z CANADIAN WAS NOT USED ELSEWHERE. THE 06Z GFS AND 00Z ECMWF HAVE COME INTO EXCELLENT AGREEMENT ON TRACKS FOR THE EXTRATROPICAL TRANSITION OF ANA...SO A BLEND OF SOLUTIONS WAS USED DAYS 3-5. THE 00Z ECMWF WAS AN OUTLIER WITH ITS INTENSE LOW PERSISTING JUST OFF THE WEST COAST OF CANADA...SO THE MEAN WAS USED TO MITIGATE THE UNCERTAINTY. THE MODELS AND ENSEMBLES HAVE BETTER AGREEMENT OVER THE CENTRAL TO EASTERN US DAYS 3-5...WHERE A 06Z GFS/00Z ECMWF BLEND WITH THEIR RESPECTIVE 00Z GEFS/00Z ECMWF ENSEMBLE MEANS WAS USED. AGREEMENT IS GOOD ON LOW PRESSURE DEVELOPING IN THE PLAINS AND MOVING INTO THE UPPER MS VALLEY MONDAY AND THEN ACROSS THE UPPER LAKES AND ONTARIO TUE, WITH A TRAILING FRONT MOVING INTO THE OH VALLEY. THE FRONT THEN PROGRESSES DOWNSTREAM ACROSS THE LAKES AND NORTHEAST, WITH THE SURFACE REFLECTION WEAKENING FURTHER SOUTH AS THERE ISN'T MUCH IN THE WAY OF HEIGHT/PRESSURES FALLS IN THE SOUTHERN APPALACHIANS/SOUTHEAST NEXT WED/THU. THE 06Z GFS/GEFS GREATER AMPLIFICATION OF THE MID-UPPER TROUGH ACROSS THE UPPER MS VALLEY NEXT THU 30 OCT APPEARS TO BE A DOMINO EFFECT DOWNSTREAM FROM THE MORE AMPLIFIED EASTERN PACIFIC PATTERN...WITH CONFIDENCE LOW IN THESE SOLUTIONS. ELSEWHERE... A CONSENSUS LOOKS GOOD FOR A CLOSED LOW DEPARTING NRN NEW ENGLAND ON SUNDAY ACROSS THE CANADIAN MARITIMES. ...SENSIBLE WEATHER HIGHLIGHTS... AN AREA FROM THE CNTRL/S-CNTRL PLAINS EWD ACROSS THE MID-UPPER MS VALLEY INTO THE GRTLKS SHOULD BE FAVORED FOR SHOWERS/THUNDERSTORMS DURING A PERIOD CNTRD AROUND TUE. CONTINUE TO EXPECT WELL ABOVE NORMAL TEMPS AHEAD OF THE SFC FRONT WITH A COUPLE OF DAYS OF PLUS 10-20F ANOMALIES FROM THE PLAINS ACROSS THE LOWER-MID MS VALLEY AND INTO THE TN VALLEY/OH VALLEY. THE NEGATIVE TEMP ANOMALIES ARE MUCH MORE LIMITED IN SCOPE...FOCUSING ON THE CENTRAL TO NORTHERN ROCKIES DAYS 4-5 BEFORE THE AIRMASS WARMS AND REVERTS CLOSER TO NORMAL VALUES DAYS 6/7. TEMPS REMAIN ABOVE NORMAL IN THE SOUTHERN PLAINS THROUGH THE END OF THE PERIOD NEXT THU 30 OCT. ON WED THE SHOWERS/STORMS PROGRESS ACROSS THE GREAT LAKES/OH VALLEY/LOWER MS VALLEY AND THEN THE SHOWERS REACH THE EAST COAST ON THU. MSTR AND AREAS OF RAIN WILL RETURN TO THE PAC NW/NORTHWEST CA AHEAD OF THE LOW PRESSURE FORMING FROM THE EXTRATROPICAL MERGER OF ANA WITH THE MID-LATITUDE PAC SYSTEM. SHOWERS EXTEND INLAND INTO THE NORTHERN ROCKIES SUN. ONCE THE MEAN TROUGH AND POTENTIAL EMBEDDED CLOSED LOW APPROACH THE NORTHWEST NEXT THU 30 OCT...SHOWERS MAY REDEVELOP OVER THE NORTHWEST TO NORTHERN CA WED-THU. NO ARCTIC INTRUSIONS SEEM LIKELY FOR SOME TIME TO COME...WITH THE PRIMARY THREAT FOR HEAVY SNOW IN THE WASHINGTON CASCADES. PETERSEN/RAUSCH