ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 148 PM EST SUN DEC 21 2014 VALID 12Z THU DEC 25 2014 - 12Z MON DEC 29 2014 A STORMY MEDIUM RANGE IS STILL PROMISED BY THE GLOBAL NUMERICAL MODELS FOR THE ALEUTIANS AND BERING SEA. WITH TIME, THE ENSEMBLE MEANS SHOW A GRADUAL RISE IN HEIGHTS ACROSS THE GULF OF ALASKA AND THE EASTERNMOST BERING SEA, SIGNALLING A PATTERN CHANGE TOWARD THE END OF THE MONTH. THE GUIDANCE AT WEEK 2 IS DOMINATED BY SOLUTIONS THAT INDICATE A NEGATIVE ARCTIC OSCILLATION, WHICH INVARIABLY MEANS THE BUILDING OF AN UPPER RIDGE OVER THE YUKON AND ALASKAN INTERIOR. THE EUROPEAN CENTRE GUIDANCE HAS PROVEN FAR STEADIER THAN THE GFS SOLUTIONS FOR THE PERIOD JUST PRIOR TO THE PATTERN CHANGE--ESSENTIALLY THE CURRENT MEDIUM RANGE. HAVE ATTEMPTED TO SALVAGE WHAT IS USABLE FROM THE VARIOUS OPERATIONAL RUNS OF THE ECMWF, MOSTLY TO GIVE THE CYCLONIC GRADIENTS MORE OOMPH THAN THE WASHED OUT ENSEMBLE MEANS. IN THE CASE OF THE 00Z/21 ECMWF, FOUND THAT IT WAS SERVICEABLE WHEN BLENDED EVENLY WITH THE ECENS MEAN FROM THE SAME DATA CYCLE THROUGH ABOUT 168 HOURS--AFTER WHICH IT SENDS SIGNIFICANTLY MORE HEIGHT FALLS ACROSS THE GULF THAN THE MEAN. CISCO