ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 245 PM EDT SUN AUG 21 2016 VALID 12Z THU AUG 25 2016 - 12Z MON AUG 29 2016 ASIDE FROM GUIDANCE SHOWING BETTER CLUSTERING FOR THE EXTRATROPICAL EVOLUTION OF KOMPASU/MINDULLE TRACKING INTO THE BERING SEA EARLY IN THE PERIOD... FCST CONFIDENCE IS KEPT AT OR BELOW AVG BY DAY TO DAY VARIABILITY IN THE MODELS AND SIGNIFICANT MODEL/ENSEMBLE SPREAD. THE MOST PROMINENT IDEA THAT SHOWS UP IN TODAY'S GUIDANCE IS GREATER POTENTIAL FOR FLOW SEPARATION... BOTH WITH THE UPR TROUGH THAT BECOMES ESTABLISHED JUST W OF 160W IN THE SHORT RANGE AND WITH FLOW EMERGING FROM ERN SIBERIA. AS THE INITIAL TROUGH SPLITS NEAR THE ERN ALEUTIANS/60N LATITUDE LATEST OPERATIONAL RUNS SHOW SOME ENERGY TRACKING ACROSS/NEAR THE GULF OF ALASKA AROUND THE NERN PAC RIDGE BUT WITH TIMING/AMPLITUDE DIFFS... WHILE AN UPR LOW LINGERS TO THE S OF THE ALEUTIANS. YET TO BE DETERMINED IS TO WHAT EXTENT ENERGY REACHING THE BERING SEA FLOWS SWD AND ULTIMATELY INTERACTS WITH THE UPR LOW OVER THE PAC. INDIVIDUAL MODELS AND ENSEMBLE MEANS STILL VARY WIDELY WITH CMC/EC MEANS (PLUS TO A REASONABLE DEGREE NAEFS MEANS) AND RECENT OPERATIONAL EC RUNS MAINTAINING THE BEST CONTINUITY OVER THE PAST 24 HRS FOR THIS EVOLUTION. LEANING MORE TOWARD THE MEANS PROVIDES A MORE STABLE SOLN RELATIVE TO DETAILS FROM INDIVIDUAL EC RUNS. INCLUDING SOME OPERATIONAL GUIDANCE DAYS 4-5 THU-FRI PROVIDES THE HINT OF A SHRTWV CROSSING THE GULF OF ALASKA AND THE PANHANDLE WITHOUT COMMITTING TO AN INDIVIDUAL SOLN... AND ELSEWHERE MODEL DIFFS CANCEL ENOUGH TO YIELD A SOLN THAT IS STILL FAIRLY SIMILAR TO THE NAEFS/EC MEANS. MEANWHILE THERE IS A MORE PROGRESSIVE TREND IN THE MEANS FOR FLOW ALONG/N OF 60N LATITUDE... IN CONTRAST TO PRIOR FCSTS SHOWING A TROUGH SETTLING NEAR THE WEST COAST OF THE MAINLAND. AS A RESULT CURRENT EXPECTATION IS FOR SOME AMOUNT OF SHRTWV ENERGY TO CROSS THE MAINLAND AROUND DAYS 5-6 FRI-SAT FOLLOWED BY A MODEST RIDGE. THEN ENERGY EJECTING FROM THE AMPLIFIED ERN ASIA TROUGH MAY BEGIN TO APPROACH THE BERING STRAIT AND VICINITY LATE IN THE PERIOD. BY MID-LATE PERIOD THE ENSEMBLE MEANS PROVIDE THE BEST OPTION TO REFLECT SOME OF THE LATEST GUIDANCE TRENDS WHILE AVOIDING THE GREATER SPREAD AND VARIABILITY SEEN IN RECENT OPERATIONAL MODEL RUNS. TELECONNECTIONS RELATIVE TO THE WRN ATLC RIDGE THAT HAS BEEN A FAIRLY PERSISTENT FEATURE FOR A WHILE SUGGEST THAT THE DOWNSTREAM PAC PATTERN SHOULD HAVE A LONGER WAVELENGTH THAN FCST BY 00Z/06Z GEFS MEANS. THIS FAVORS LEANING AWAY FROM THE GEFS MEANS. THAT SAID... THERE ARE OTHER INDIVIDUAL SOLNS THAT ALSO HAVE SHORTER WAVELENGTHS. THE NAEFS MEAN PROVIDES THE MOST CONSERVATIVE WAY TO INCORPORATE POTENTIAL EVOLUTIONS THAT DIFFER FROM THE 00Z CMC/ECMWF MEANS. RAUSCH