ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 247 PM EST SUN DEC 18 2016 VALID 12Z THU DEC 22 2016 - 12Z MON DEC 26 2016 ...GUIDANCE/UNCERTAINTY ASSESSMENTS... THE DETERMINISTIC GLOBAL MODELS IN PARTICULAR CONTINUE TO OFFER SIGNIFICANT RUN TO RUN VARIANCE WITH DEEPENED SURFACE LOW/FRONTAL SYSTEM EMPHASIS OVER THE SRN BERING SEA AND WITH ENERGY TRANSFER AND POTENT EMERGENCE DOWNSTREAM INTO A STORMY NRN GULF OF AK. MODEL SPREAD IS EVEN GREATER FARTHER NORTH WITH RECENT ECMWF LED SOLUTIONS SUGGESTING AN ARCTIC LOW TO THE NORTH OF ALASKA WILL ULTIMATELY HEAD WEST COMPARED TO A GFS FORECAST CAMP THAT SHOWS MORE OF A LATER WEEK EASTWARD PROGRESSION. OVERALL...THIS GENERALLY LENDS A MORE CONSERVATIVE ENSEMBLE MEAN FORECAST APPROACH FOR THE WPC ALASKAN MEDIUM RANGE PRODUCT SUITE. EVEN THE VARIOUS ENSEMBLE MEANS OFFER SOME LARGER THAN NORMAL DIFFERENCES SO DECIDED TO BASE WPC GUIDANCE MAINLY ON THE 06/12 UTC GEFS MEAN THAT MAINTAIN MAX WPC CONTINUITY FROM YESTERDAY. DID OPT TO INCLUDE SOME MANUAL MODIIFICATIONS TO ADD SOME LOCAL DETAIL/OFFSHORE LOW DEPTH CONSISTENT WITH UPPER SUPPORT. CLIMATOLOGY WAS ALSO INFUSED SOME FOR THE HIGH RESOLUTION SENSIBLE WEATHER GRIDS TO COUNTERBALANCE BIAS CORRECTIONS THAT HAS NOT YET ADJUSTED TO THIS TRANSITIONAL PATTERN COMPARED TO RECENT MORE ENTRENCHED FLOW. ...PATTERN OVERVIEW AND WEATHER HIGHLIGHTS/THREATS... THIS PATTERN SHOULD PROVE PERIODICALLY WET AND HIGHLY UNSETTLED FROM THE ALEUTIANS/SW AK TO SRN/SERN AK. THIS SHOULD BE ESPECIALLY TRUE OVER FAVORED COASTAL TERRAIN WITH APPROACH OF THESE HIGH PCPN/WIND/WAVES FOCUSING SERIES OF STORMS THIS WEEK. ARCTIC LOW PROMIMITY COULD LEAD TO UNSETTLED FLOW INTO THE NORTH SLOPE MID-LATE WEEK. MODEL AND ENSEMBLE TRENDS REAMPLIFY THE FLOW NEXT WEEKEND LENDING DEEP BERING SEA LOW DEVELOPMENT POTENTIAL AND A RISING HEIGHT FIELD UP THROUGH THE INTERIOR. SCHICHTEL