ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 429 PM EDT SAT SEP 03 2016 VALID 12Z WED SEP 07 2016 - 12Z SUN SEP 11 2016 ...ALASKAN GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER HIGHLIGHTS/THREATS... THE WETTEST FLOW DURING THE MEDIUM RANGE PERIOD FOCUS FROM SRN TO ESPECIALLY SERN AK TUE/WED WITH REDEVELOPMENT THU/FRI AS A SERIES OF EJECTING SHORT WAVE TROUGHS TRACK OVER THE SRN TIER OF THE STATE/GULF OF AK. NRN STREAM HEIGHT FALLS OVERTOP SHOULD ACCOMPANY A STRONG COLD FRONT ACROSS THE INTERIOR. AN ARCTIC UPPER VORTEX AND UPPER TROUGHING OVER THE STATE WILL BE RATHER CONSTANT FEATURES MOST OF THE PERIOD...ALLOWING THE AFOREMENTIONED COLD FRONT TO REACH THE SRN AK. A SECOND COLD FRONT IS EXPECTED TO DIG SEWD INTO NW/NRN AK THEN THE INTERIOR DAYS 6-8 FRI/NEXT WEEKEND WITH RENEWED ARCTIC TROUGH DEVELOPMENT ALOFT. THE MORE UNCERTAIN PART OF THE FCST PERIOD REMAINS WITH THE A MAIN SYSTEM TRACK ACROSS NRN AND NERN PAC NEWD TOWARD ALASKA. A LARGE UPPER RIDGE OVER THE ERN PAC WILL DRAW NORTH SMALL SCALE SHORT WAVE IMPULSES INCLUDING POSSIBLE TROPICAL ENTITY LESTER...WHICH WILL BE AHEAD OF AN UPPER TROUGH ORGANIZING AND AMPLIFYING DOWN 180W. THE GFS REMAINS MORE PROGRESSIVE THAN THE ECMWF WITH SYSTEMS SLIDING UP OVER THE RIDGE TOWARD THE NERN PAC/GULF OF AK. THE MEANS TEND TO SUPPORT EACH OPERATIONAL SOLUTION AND THE FURTHER OUT IN TIME THE PATTERN ONLY BECOMES MORE CHAOTIC. HOWEVER...THE ENSEMBLE MEANS OFFER MUCH BETTER CONTINUITY AND ARE MORE COMPATABLE THAN THE DETERMINISTIC MODELS BEYOND DAY 4/WED. THIS MAY PROVE AN UNSETTLED/WET PATTERN ACROSS THE ALEUTIANS AND ALASKAN SW AND SRN/SERN TIER ALL NEXT WEEK. ACCORDINGLY...THE WPC MEDIUM RANGE ALASKAN PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE GFS/ECMWF/ENSEMBLE BLEND WED WITH TRANSITION TO MAINLY A BLEND OF THE 06 UTC GEFS MEAN AND 00 UTC NAEFS/ECMWF ENSEMBLE MEANS THEREAFTER CONSISTENT WITH GROWING UNCERTAINTY. SCHICHTEL