ALASKA EXTENDED FORECAST DISCUSSION...CORRECTED PARAGRAPH 3 NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 310 PM EDT TUE SEP 30 2014 VALID 12Z SAT OCT 04 2014 - 12Z WED OCT 08 2014 SYNOPTIC PATTERN ACROSS HIGH LATITUDES DURING THE MEDIUM RANGE PERIOD SUGGESTS TROUGHING ACROSS NORTHEAST SIBERIA WILL PROGRESS SLOWLY EASTWARD THROUGH TIME---ANCHORING IN THE SOUTHERN BERING SEA AROUND MID PERIOD. TO GET TO THIS DAY 5-6 MID-PERIOD TIME FRAME...MUCH HAS YET TO SETTLE OUT DOWNSTREAM. THE SHORT-TERM CONCERNS WITH 'KAMMURI' DO INFLUENCE THE GULF OF ALASKA...DICTATE THE OUTCOME OF THE LEAD UPPER-LEVEL TROUGH PROGRESSION...AND EVENTUAL EAST-NORTHEASTWARD MIGRATION OF A SHORTWAVE UPPER-LEVEL RIDGE CURRENTLY INVOF 140W---INTO THE YUKON AND BC. THE ECMWF/GFS GENERALLY SET THE TONE HEADING INTO DAY 4...AS THE SURFACE WAVE ENERGY MIGRATING THROUGH THE SOUTHEAST INTERIOR AND PANHANDLE BEGIN TO NUDGE THE SHORTWAVE RIDGE INTO CANADA. BUT CONFIDENCE IS LOW IN THAT 'PERFECT PROG' SCENARIO FOR THE FLOW PATTERN TO TRANSITION ACROSS THE GULF OF ALASKA. A BUSY AND ACTIVE TROPICAL AND SUBTROPICAL WESTERN PACIFIC THIS MEDIUM RANGE PERIOD WILL CONTINUE TO THROW RUN-TO-RUN UNCERTAINTY INTO THE MID-LATITUDE WESTERLY FLOW PATTERN ALOFT BEYOND DAY 5---ESPECIALLY WITH THE POTENTIAL FOR MID-LATITUDE CYCLOGENESIS INVOF THE DATELINE AND 45N-50N LATITUDE. THE KAMCHATKA REGION AND SOUTHERN BERING SEA SHOULD BE RATHER ACTIVE...WITH AN APPROACHING UPPER-LEVEL COLD CORE AND ASSOCIATED SURFACE LOW IN A POSITION FAVORABLE FOR ENTRAINMENT OF REMNANT 'PHANFONE' MOISTURE AND ENERGY. THIS ADDS A CONSIDERABLE AMOUNT OF UNCERTAINTY IN THE MEDIUM RANGE. NOT ONLY WITH THE DEPTH...STRUCTURE AND LOCATION OF THE PARENT CYCLONE IN THE SOUTHERN BERING SEA...BUT ALSO WITH THE REGION OF SECONDARY CYCLOGENESIS DOWNSTREAM ALONG 50N BETWEEN THE DATELINE...165W LONGITUDE AND EVENTUALLY...THE GULF OF ALASKA PROPER. ALTHOUGH THE 30/00Z ECENS MEAN AND 30/06Z GEFS GENERALLY AGREE WHERE THE PARENT UPPER-LEVEL CYCLONIC CIRCULATION WILL SETTLE IN THE SOUTHERN BERING SEA...CYCLOGENESIS ALONG THE BASE OF THE UPPER-LEVEL TROUGH...IS HANDLED VERY DIFFERENTLY BETWEEN THE ECMWF...GFS AND CANADIAN AROUND THE 6/00Z TIME FRAME. FOR NOW...BLENDED THE ENSEMBLE MEANS MENTIONED ABOVE FOR DAYS 4-8. SUSPECT THE FORECAST FOR EARLY NEXT WEEK WILL CHANGE...ALTERED BY THE FLOW TRANSITIONING ACROSS THE GULF OF ALASKA IN THE SHORT TERM. GIVEN THE VAST MODEL DIFFERENCES WEST OF THE DATELINE IN THE MID-LATITUDE PACIFIC AND ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE IN THE MEDIUM RANGE---POSSIBLE PHASING CONCERNS---OFFER A MUCH LOWER THAN NORMAL CONFIDENCE LEVEL FORECAST. VOJTESAK