ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 231 PM EDT WED SEP 03 2014 VALID 12Z SUN SEP 07 2014 - 12Z THU SEP 11 2014 THE DEEP STORM FCST TO BE JUST S OF THE CNTRL ALEUTIANS AS OF EARLY DAY 4 SUN REMAINS THE PRIMARY FEATURE OF INTEREST DURING THE DAYS 4-8 PERIOD. THERE IS GENERALLY BETTER THAN AVERAGE CLUSTERING OF MODEL/ENSEMBLE SOLNS THROUGH THE MIDDLE OF NEXT WEEK BUT CONFIDENCE IN ANY SPECIFIC SCENARIO DECREASES AFTER DAY 5 MON AS AMPLIFYING ERN SIBERIAN/BERING SEA ENERGY IS FCST TO INTERACT WITH THE INITIAL SYSTEM LEADING TO MEANINGFUL DETAIL DIFFS. THE PAST DAY OF GUIDANCE CONTINUES A RECENT TENDENCY FOR OPERATIONAL SOLNS AS A WHOLE TO LEAD THE ENSEMBLE MEANS IN STRENGTH... AS WELL AS FOR TRENDS TOWARD SLOWER TIMING DUE IN PART TO GREATER POTENTIAL FOR FLOW WITHIN THE OVERALL MEAN TROUGH ALOFT TO REMAIN FAIRLY WELL SEPARATED AFTER UPSTREAM FLOW BECOMES INCORPORATED INTO THE SYSTEM. THIS SEPARATION ALSO ALLOWS FOR A GREATER SEWD EXTENT OF THE SFC FRONT REACHING THE NRN MAINLAND. TODAYS DIFFS BETWEEN THE MEANS AND THE AVG OF OPERATIONAL FCSTS IS GENERALLY FOR THE LATTER TO TRACK THE SFC LOW A LITTLE SWD OF THE MEANS MID-LATE PERIOD. THE 12Z GFS HAS ADJUSTED TOWARD THE MEANS THOUGH. AFOREMENTIONED BEHAVIOR OF THE MDLS VS THE MEANS SEEMS TO SUPPORT INCLUDING SOME OPERATIONAL GUIDANCE THROUGH THE END OF THE PERIOD IN CONTRAST TO TYPICAL VERIFICATION/STABILITY FAVORING ENSEMBLE MEAN EMPHASIS AT THAT TIME. BEFORE DOWNSTREAM RIDGING BUILDS INTO THE NERN PAC AND PARTS OF MAINLAND ALASKA/NWRN CANADA... A COMPACT UPR SYSTEM IS FCST TO SUPPORT A SFC WAVE NEAR THE SERN COAST DAY 4 SUN. OPERATIONAL MODELS AGREE FAIRLY WELL UPON A MORE CLOSED UPR SYSTEM AND BETTER DEFINED SFC LOW THAN THE MEANS. BASED ON OPERATIONAL MODEL AGREEMENT FOR BOTH FEATURES OF INTEREST EARLY IN THE PERIOD... DAYS 4-5 SUN-MON REFLECT AN AVG OF THE 06Z-12Z GFS AND 00Z ECMWF/CMC. DAYS 6-7 TUE-WED INCORPORATE SOME 06Z GEFS/00Z ECMWF MEAN GUIDANCE ALONG WITH THE 12Z GFS/00Z ECMWF TO ACHIEVE THE DESIRED MODEL/ENSMEAN COMPROMISE. THE 12Z GFS IS PHASED OUT DURING DAY 8 THU DUE TO LOWER CONFIDENCE IN ITS DETAILS. RAUSCH