ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 250 PM EST SAT NOV 11 2017 VALID 12Z WED NOV 15 2017 - 12Z SUN NOV 19 2017 ...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER/THREAT HIGHLIGHTS... IT REMAINS THE CASE THAT AN AMPLIFIED MID-UPPER LEVEL MEAN RIDGE IS EXPECTED TO CENTER OVER THE BERING SEA/STRAIT AND INTO WRN AK FOR MUCH OF THE UPCOMING WEEK...REFORMING SEVERAL TIMES AFTER ENERGETIC TROUGH/LOW INTERACTIONS. 00 UTC ECMWF/ECMWF ENSEMBLES OVERALL MAINTAIN RIDGE AMPLITUDE AND WPC CONTINUITY MORE THAN RECENT GFS/GEFS RUNS. THE ECMWF CLUSTERS WELL WITH ECMWF ENSEMBLES INTO DAY 5/THU...BUT THE NEWER 12 UTC ECMWF HAS TRENDED MORE IN LINE WITH ECMWF ENSEMBLES INTO NEXT WEEKEND. AS PER COLLABORATION WITH LOCAL WEATHER FORECAST OFFICES...PREFER AMPLITUDE GIVEN UPSTREAM FLOW AND RECENT FLOW HISTORY. THE RIDGE FAVORS SHARPLY DIGGING DOWNSTREAM SHORTWAVES/HEIGHT FALLS TO SUPPORT SOME TERRAIN ENHANCED SNOWS AND COLD ARCTIC FLOW OVER THE NORTH SLOPE THEN THE E-CENTRAL INTERIOR AND SRN/SE AK. LEAD LOWS OVER THE ERN GULF OF AK NEXT WEEK SHOULD MEANWHILE MAINTAIN AN UNSETTLED MARITIME ENVIRONMENT. UPSTREAM... A SERIES OF BERING SEA LOWS WILL PROGRESS TOWARD THE ALEUTIANS AND SW/WRN AK NEXT WEEK...RIDING TO THE MEAN RIDGE POSITION. SUPPORTING DYNAMICS OFFER POTENTIAL FOR DEEPENED LOWS IN THIS FLOW AND SUBSEQUENTLY DOWNSTREAM WITH GULF OF AK ENERGY TRANSFER. WPC PROGS OFFER MORE MODEST SYSTEMS FOR NOW GIVEN FORECAST UNCERTAINTY AND INHIBITING RIDGE CHARACTERISTICS...ALBEIT WITH INCREASING POTENTIAL DAYS 7/8 WITH POSSIBLE PATTERN TRANSITION/RETROGRESSION. ACCORDINGLY...THE WPC ALASKAN MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A 50-50 BLEND 00 UTC ECMWF/ECMWF ENSEMBLES DAYS 4/5 WED-THU. FORECAST SPREAD INCREASES WITH EMBEDDED FEATURES THEREAFTER SO OPTED TO TRANSITION QUICKLY TO USING MOSTLY THE 00 UTC ECMWF ENSEMBLE MEAN DAYS 6-8 FRI THROUGH NEXT WEEKEND. 12 UTC ECMWF TRENDS MORE IN LINE WITH THIS WPC/WFO BASED SOLUTION SEEMS TO BOLSTER FORECAST CONFIDENCE. SCHICHTEL