ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 226 PM EDT SUN APR 26 2015 VALID 12Z THU APR 30 2015 - 12Z MON MAY 04 2015 AFTER A PERIOD OF LARGE ENSEMBLE SPREAD... IT APPEARS THAT THE GUIDANCE IS SHOWING SIGNS OF COMING TOGETHER TOWARD A MAINTAINING AN UPPER LOW IN THE BERING SEA. DOWNSTREAM OVER THE GULF... THE PATTERN IS MUCH MORE CHANGEABLE WHICH LEAVES ROOM FOR MORE ERROR IN SYSTEM EVOLUTION. TO THE NORTH... WEAK RIDGING IS EXPECTED TO LINGER JUST NW OF THE NORTH SLOPE. MODELS/ENSEMBLES HAVE LARGELY TRENDED A BIT SLOWER... ABOUT 12-18 HRS... FROM THU/D4 ONWARD WITH THE PATTERN. ECMWF DROPPED ITS IDEA OF A QUICKER/PHASED AND MORE NORTHERN-STREAM DOMINATED SYSTEM ALONG THE ALEUTIANS THU-FRI IN FAVOR OF A SLOWER AND SOUTHERN-ORIGIN LOW THAT THE MODELS BASICALLY ALL SHOW. OUT OF SYNC GFS RUN FROM THE 25TH TRENDED TOWARD THE ECMWF/CONSENSUS FROM YESTERDAY BUT STILL SHOWS A MORE DEFINED NORTHERN LOW ON THU/D4 THAT IS NOT OUT OF THE QUESTION... BUT SHOULD SHEAR OUT BY FRI/D5 AS THE OTHER SYSTEM DEEPENS. THAT SHOULD TRACK NORTHEASTWARD TOWARD AND INTO THE GULF NEXT WEEKEND THOUGH THE QUASI-SPLIT FLOW MAY TUG IT MORE NORTHWARD OR EASTWARD DEPENDING ON DETAILS. FOR NOW... LET THE ENSEMBLES LEAD THE WAY -- 06Z GEFS AND 00Z ECENS MEAN -- TAKING THE LOW NORTHEASTWARD AND DISSIPATING. 12Z GFS ACTUALLY SHOWS A BETTER PROGRESSION THAN THE ECMWF HERE BUT GIVEN THE CHANGEABILITY OF RECENT MODEL RUNS CANNOT RULE ANYTHING OUT. FOR NEXT SUN-MON... ENSEMBLES AND MODELS SHOW GOOD AGREEMENT FOR THAT TIME RANGE BRINGING IN ANOTHER UPPER/SFC LOW INTO THE BERING SEA. FRACASSO