ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 237 PM EDT WED AUG 03 2016 VALID 12Z SUN AUG 07 2016 - 12Z THU AUG 11 2016 NEAR THE MAINLAND GUIDANCE AS A WHOLE MAINTAINS DECENT AGREEMENT IN PRINCIPLE WITH THE PATTERN DOMINATED BY A MEAN TROUGH SETTLING NEAR 160W. WITHIN THIS TROUGH THE PRIMARY UNCERTAINTY INVOLVES THE INTERACTION OF AN INITIAL ERN BERING SEA CLOSED LOW AND NRN PAC/ALEUTIANS ENERGY. FROM DAY 5 MON ONWARD THERE IS SOME LATITUDE SPREAD FOR THE RESULTING LOW SFC/ALOFT WITH ENSEMBLE MEANS THUS FAR SIGNALING A POSN TO THE N OF RECENT GFS RUNS TO SOME DEGREE. THIS LEADS TO LESS THAN EVEN WEIGHTING FOR THE GFS SCENARIO IN A DETERMINISTIC FCST BUT WITH THE UNDERSTANDING THAT IT STILL LIES WITHIN THE RANGE OF PLAUSIBLE OUTCOMES. DETAILS WILL AFFECT TIMING/DURATION BUT BROADLY SPEAKING MOST SOLNS STILL FAVOR A PERIOD OF ENHANCED RNFL ALONG THE SRN COAST. LATER IN THE PERIOD ENSEMBLE MEAN DIFFS ARE SIMILAR TO YDAY WITH THE ECMWF MEAN TRACKING THE WEAKENING UPR LOW FARTHER NWD THAN THE GEFS/CMC MEANS. AHEAD OF THE TROUGH ALOFT A SFC FRONT DRAPED ACROSS THE MAINLAND SHOULD DRIFT SLOWLY NWD WITH TIME. UPSTREAM ATTENTION IS FOCUSED ON LIKELY WRN PAC TROPICAL DEVELOPMENT AND PSBL INTERACTION WITH MID-LATITUDE FLOW EMERGING FROM ERN ASIA. UNCERTAINTY WITH DETAILS OF THIS INTERACTION LEADS TO INCREASING SPREAD AFTER ABOUT DAY 5 MON. BY THE END OF DAY 8 THU THE 00Z CMC MEAN/ECMWF BECOME THE FASTEST SOLNS WHILE A COMPROMISE BTWN THE 00Z ECMWF MEAN AND SLIGHTLY SLOWER 06Z GEFS MEAN OFFERS A GOOD INTERMEDIATE SOLN RELATIVE TO SLOWER GFS RUNS. AHEAD OF THIS SYSTEM THE 00Z ECMWF SHOWS A LEADING BERING SEA WAVE ASSOC WITH FAST-EJECTING ERN ASIA ENERGY. CURRENTLY PREFER TO LEAN AWAY FROM SUCH A WELL DEFINED LEADING SYSTEM AS RIDGING AHEAD OF THE TROPICAL SYSTEM/EVENTUAL EXTRATROPICAL EVOLUTION SEEMS TO FAVOR A WEAKER SFC REFLECTION... AS SUGGESTED BY THE SFC FRONT/TROUGH THAT RESULTS FROM A BLEND OF THE ENSEMBLE MEANS. DETAILS IN THE FIRST HALF OF THE FCST ARE STILL IN THE PROCESS OF COMING INTO FOCUS BUT THEY ARE CLOSE ENOUGH TO ALLOW FOR A 70 PCT OPERATIONAL MODEL WEIGHTING... SLIGHTLY MORE 00Z ECMWF VS 12Z GFS... FOR DAYS 4-5 SUN-MON. REMAINING 06Z GEFS/00Z ECMWF MEAN COMPONENT HELPS TO ANCHOR THE MOST AGREEABLE LARGER SCALE ASPECTS OF THE FCST. THEN 12Z DAY 6 TUE SERVES AS THE TRANSITION ON THE WAY TO A 50/50 BLEND OF THE TWO ENSEMBLE MEANS FOR THE REST OF THE FCST AS OPERATIONAL MODELS INCREASINGLY DIVERGE. RAUSCH