ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 107 PM EDT MON SEP 14 2015 VALID 12Z FRI SEP 18 2015 - 12Z TUE SEP 22 2015 PERSISTENT AND OCCASIONALLY STRONG ONSHORE FLOW WILL LIKELY CONTRIBUTE TO MORE HEAVY PRECIPITATION FOR THE ALASKA PANHANDLE THROUGH THE MEDIUM RANGE PERIOD...PARTICULARLY THIS WEEKEND. MODELS MAINTAIN RELATIVELY GOOD OVERALL CONTINUITY WITH THE UPPER TROUGH RETROGRADING FROM WESTERN CANADA TO THE GULF OF ALASKA EARLY IN THE PERIOD...WITH AN ACCOMPANYING BROAD CYCLONE THAT SLOWLY DECAYS AND PROGRESSES EASTWARD THROUGH THE REMAINDER OF THE PERIOD. MODEL DIFFERENCES BECOME INCREASINGLY APPARENT OVER THE BERING SEA HOWEVER DURING THIS PERIOD AS WELL...WITH THE 00-06Z GFS FASTER WITH PROGRESSING A SHORTWAVE TROUGH THAN THE DETERMINISTIC AND ENSEMBLE CONSENSUS. THUS...THE MODEL PREFERENCE SHIFTS AWAY FROM AN EVEN DISTRIBUTION OF DETERMINISTIC/ENSEMBLES EARLY TO MORE OF AN ECMWF/ECMWF ENSEMBLE MEAN/GEFS MEAN/NAEFS MEAN BLEND FROM DAY 5 BEYOND...WITH MOSTLY THE MEANS BY DAYS 7/8 TO ADDRESS THE GROWING SPREAD. THE PREVAILING PRECIPITATION WILL ALSO BE ACCOMPANIED BY MORE WIDESPREAD AND THICKER CLOUD COVER...THUS REDUCING INSOLATION AND MAINTAINING A SMALL DIURNAL RANGE IN TEMPERATURE. JAMES