ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 220 PM EDT TUE MAR 31 2015 VALID 12Z SAT APR 04 2015 - 12Z WED APR 08 2015 THE MOST COMMON THEME AMONG LATEST GUIDANCE ALOFT IS AN EVOLUTION OF THE PATTERN TOWARD NERN PAC TROUGHING WITH A PSBL WEAKNESS/EMBEDDED UPR LOW EXTENDING NWWD ALONG OR JUST W OF THE WRN COAST OF THE MAINLAND WHILE A MEAN RIDGE WOULD EXTEND OVER WRN CANADA INTO THE MAINLAND. HOWEVER INDIVIDUAL/MODEL DETAILS DIFFER SIGNIFICANTLY THROUGH THE PERIOD AND CONTINUITY HAS BEEN LESS THAN IDEAL. THE FIRST CONSIDERATION OF TODAYS FCST IS TO LEAN AWAY FROM THE 00Z ECMWF MEAN FOR SOME ASPECTS OF EXPECTED EVOLUTION. IN PARTICULAR IT SHOWS LESS MID-LATITUDE SEPARATION ALOFT RELATIVE TO MOST OTHER GUIDANCE NEAR OR JUST W OF 180 LONGITUDE... WHICH MAY PLAY A PART IN THAT GUIDANCE SOURCE BEING STRONGEST WITH THE DOWNSTREAM RIDGE. TRENDS OVER THE PAST 1-2 DAYS IN MOST SOLNS HAVE BEEN TOWARD LOWER HGTS/FARTHER SWD JET AXIS ACROSS THE NRN PAC/SRN BERING SEA ALONG WITH A FARTHER SWD SFC LOW TRACK THAT ULTIMATELY LEADS TO A CLUSTERING OF SOLNS NEAR OR S OF THE KENAI PENINSULA/GULF OF ALASKA BY LATE IN THE PERIOD. THERE IS ACTUALLY SOMEWHAT BETTER AGREEMENT AT THAT POINT THAN IN SOME EARLIER FCST HRS WHEN THERE IS STILL A DEBATE OVER WHETHER LOW PRES WILL CONSIST OF A LEADING NRN PAC/ALEUTIANS WAVE AND PERHAPS A TRAILING FEATURE AS PER SOME GFS/ECMWF RUNS VERSUS A MORE CONSOLIDATED SYSTEM AS DEPICTED IN THE ENSEMBLE MEANS. EARLY IN THE PERIOD AFOREMENTIONED TRENDS LEAD TO GREATER EWD PROGRESSION OF ENERGY ALOFT THAT REACHES THE ERN BERING SEA AS OF 12Z DAY 4 SAT. THE MODEST MAJORITY OF GUIDANCE SHOWS A DEFINED SFC WAVE REACHING JUST E OF KODIAK ISLAND BY 12Z DAY 5 SUN. HOWEVER THIS AND OTHER BERING SEA/MAINLAND DETAILS REMAIN UNCERTAIN EARLY IN THE PERIOD... AS REFLECTED BY MAJOR DIFFS JUST BTWN THE 00Z/06Z AND NEW 12Z GFS RUNS. BASED ON OBSERVED TRENDS AND GEFS/NAEFS MEAN SOLNS THAT ARE MORE SIMILAR TO WPC CONTINUITY... COMBINED WITH POOR AGREEMENT AMONG OPERATIONAL RUNS BOTH BTWN THEMSELVES AND THE ENSMEANS... PREFER TO START WITH AN EVEN BLEND OF THE 06Z GEFS/00Z NAEFS MEANS TO RESOLVE THE CURRENT SPREAD IN THE GUIDANCE. THERE IS PLENTY OF ROOM FOR AN ALTERNATIVE SCENARIO WITH ONE OR MORE SYSTEMS BUT AT LEAST THIS SOLN PROVIDES DECENT STABILITY WHILE WAITING FOR ANY ADJUSTMENTS THAT CAN BE MADE WITH SUFFICIENT CONFIDENCE. RAUSCH