ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 250 PM EDT FRI JUN 26 2015 VALID 12Z TUE JUN 30 2015 - 12Z SAT JUL 04 2015 WITHIN A LARGE SCALE PACIFIC/NOAM MEAN PATTERN THAT SHOWS HINTS AT GRADUAL RETROGRESSION WITH TIME... COMBINED UNCERTAINTIES CONTINUE TO CAUSE SIGNIFICANT SPREAD AND/OR RUN TO RUN CHANGES IN LATEST AND RECENT GUIDANCE. FEATURES CONCERNED INCLUDE AN UPR LOW INITIALLY S OF THE MAINLAND... A MEAN TROUGH OVER/JUST W OF THE WRN MAINLAND... ONE OR MORE BUNDLES OF ENERGY CARRIED ALONG MID-LATITUDE PAC FLOW... AND AN UPR LOW NEAR KAMCHATKA AS OF EARLY TUE. FOR THE NERN PAC UPR LOW THE SOLNS RANGE FROM QUICK EJECTION IN GFS RUNS TO A STNRY/WWD 00Z CMC WHICH ALLOWS FURTHER INTERACTION WITH HIGHER LATITUDE ENERGY AS WELL AS NRN PAC FLOW. THE 00Z ECMWF IS MOST SUSPECT AS IT BRINGS THE UPR LOW INTO A CONSENSUS MEAN RIDGE AROUND WED-THU. MEANWHILE THE FULL RANGE OF MODEL/ENSEMBLE GUIDANCE IS NOT AS AGGRESSIVE AS GFS/CMC RUNS WITH THE SWD DIGGING OF ENERGY FROM THE WRN MAINLAND TROUGH. THUS FOR NOW PREFER TO LEAN AWAY FROM AGGRESSIVE GFS/CMC RUNS WITH THIS ENERGY ALOFT AND THEIR SFC SOLN THAT HAS GREATEST IMPACT ALONG THE SRN COAST. THIS LEADS TO A FAVORED BLEND INCORPORATING THE 00Z ECMWF/NAEFS MEANS AND 06Z GEFS MEAN THAT ARE ABOUT A DAY SLOWER AND EVENTUALLY SOMEWHAT WWD VERSUS THE 12Z GFS FOR THE CNTRL PAC SYSTEM THAT MAY TRACK TOWARD THE PENINSULA/KODIAK ISLAND. HOWEVER AT SOME FCST HRS A SLOWER TIME-SHIFTED 12Z GFS COULD PROVIDE SOME INPUT FOR ADDING DEFINITION TO THE ENSMEAN BLEND WHICH IS ADMITTEDLY WEAKER THAN DESIRED. WITH THAT CAPABILITY LACKING FOR PRODUCING THE MANUAL FCSTS... ATTEMPTED TO INCORPORATE SOME MANUAL ADJUSTMENT FROM THE INITIAL BLEND. NOTE THAT THE 00Z ECMWF IS A SRN EXTREME WITH THIS SYSTEM. UPSTREAM THE 00Z ECMWF ALSO COMPARES POORLY TO OTHER GUIDANCE IN KEEPING ITS UPR LOW OVER THE EXTREME WRN BERING SEA MOST OF THE PERIOD. REMAINING SOLNS SUGGEST GREATER MOVEMENT OF THE CLOSED LOW ENERGY BUT DO NOT YET AGREE AS TO WHAT PROPORTION SHEARS E/SE VERSUS TRACKING N/W AROUND THE UPR HIGH TO ITS N. REGARDING THE SYSTEM THAT COMES INTO THE PICTURE DURING THE LATTER HALF OF THE PERIOD... SOME INDIVIDUAL MODEL RUNS/ENSEMBLE MEMBERS ARE ON THE FASTER SIDE LIKE THE LATEST ECMWF MEANS BUT ENOUGH OF A SPLIT EXISTS TO RECOMMEND A COMPROMISE TIMING AS PROVIDED BY THE FAVORED ENSMEAN BLEND. COMPARED TO YDAYS FCST THE MOST SIGNIFICANT ADJUSTMENT IS TOWARD A MORE SUPPRESSED CNTRL PAC SYSTEM EARLY-MID PERIOD... WITH LATEST SOLNS ADDING SOME CONFIDENCE TO YDAYS 12Z/25 ECMWF-EC MEAN GUIDANCE THAT HAD ADJUSTED TOWARD SOME OTHER SOLNS THAT HAD BEEN INDICATING A MORE SRN TRACK. GIVEN THE COMPLEXITIES STILL PRESENT IN THE FCST EVOLUTION THERE REMAINS GREATER THAN AVG POTENTIAL FOR FURTHER SIGNIFICANT CONTINUITY CHANGES. RAUSCH