ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 254 PM EDT TUE APR 19 2016 VALID 12Z SAT APR 23 2016 - 12Z WED APR 27 2016 MODELS/ENSEMBLES AGREE IN PRINCIPLE ON THE LARGE SCALE MEAN PATTERN. THE MOST PROMINENT FEATURES SHOULD BE A WRN CANADA RIDGE THAT MAY EXTEND INTO A PORTION OF MAINLAND ALASKA AND A BROAD AREA OF RELATIVELY LOW HGTS ALOFT CONTAINING ONE OR MORE UPR LOW CENTERS COVERING THE NRN-NERN PAC AND ALEUTIANS/SRN BERING SEA. WHILE THERE IS FAIR CONSENSUS ON MEAN FLOW... DETAIL DIFFS ACROSS THE NRN-NERN PAC DEVELOP ALREADY IN THE SHORT RANGE AND PERSIST THROUGH THE EXTENDED FCST. AS A RESULT TODAY'S FCST MAINTAINS GREATER EMPHASIS ON THE ENSEMBLE MEANS TO PROVIDE REASONABLY GOOD CONTINUITY UNTIL CONFIDENCE FOR FINER DETAILS IMPROVES. PREFERENCE AMONG THE MEANS IS FOR THE 00Z ECMWF MEAN AS IT IS DEEPER SFC/ALOFT OVER AND NEAR THE ALEUTIANS THROUGH THE WEEKEND AND IS THE ONE ENSMEAN SOLN THAT MAINTAINS A DISCRETE WRN PAC-ALEUTIANS SYSTEM THROUGH DAY 8 WED... VS GEFS/NAEFS MEANS THAT MERGE THIS WRN SYSTEM INTO THE ERN AREA OF LOW PRES AROUND MON-TUE. THE 00Z ECMWF IS CLOSE ENOUGH TO THE FAVORED SCENARIO TO INCLUDE A GRADUALLY DECLINING 30-10 PCT WEIGHTING FROM DAY 4 SAT INTO DAY 7 TUE. AS FOR SOME FCST DETAILS... IT REMAINS TO BE SEEN HOW MUCH LOW PRES WILL END UP IN THE EXTREME NERN PAC SUCH AS FCST BY RECENT GFS/CMC RUNS. SOME INDIVIDUAL ENSEMBLE MEMBERS BRING A SFC LOW THAT FAR EWD BUT THE OVERALL MEANS WOULD HAVE ONLY A WEAKENING FRONT EXTENDING TO THE E OF KODIAK ISLAND. GIVEN THE FAIRLY STABLE DOWNSTREAM RIDGE... WOULD LIKE TO LEAN AWAY FROM THESE ERN LOW SOLNS UNTIL OTHER GUIDANCE TRENDS IN THAT DIRECTION. UPSTREAM THE MEANS GENERALLY SUPPORT THE IDEA OF A MID-LATITUDE PAC WAVE DEVELOPING/TRACKING TO A POSITION JUST S OF THE ERN ALEUTIANS BY SUN-MON THOUGH NOT NECESSARILY TO THE DEPTH SEEN IN THE 00Z/19 AND 12Z/18 ECMWF RUNS. THERE IS A DECENT SIGNAL FOR THE LATE PERIOD WRN PAC-ALEUTIANS SYSTEM ALBEIT WITH TRACK/TIMING SPREAD THAT IS TYPICALLY BROAD FOR A DAYS 7-8 FCST. MOST SOLNS ARE SIMILAR WITH THE SFC PATTERN OVER THE MAINLAND IN SPITE OF DIFFS IN WWD EXTENT OF THE WRN CANADA MEAN RIDGE ALOFT. RAUSCH