ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 146 PM EST FRI NOV 28 2014 VALID 12Z TUE DEC 02 2014 - 12Z SAT DEC 06 2014 THERE IS DECENT AGREEMENT AMONG GUIDANCE IN THE LARGE SCALE PATTERN BUT A NUMBER OF IMPORTANT MEDIUM TO SMALLER SCALE DETAIL ISSUES MAY TAKE A WHILE TO RESOLVE SATISFACTORILY. A MEAN RIDGE IS FCST TO BECOME ESTABLISHED OVER EXTREME WRN CANADA AND EXTEND INTO THE SERN MAINLAND AHEAD OF AN UPR LOW ASSOC WITH A FAIRLY DEEP SYSTEM OVER THE BERING SEA EARLY IN THE WEEK. MEANWHILE ENERGY FLOWING AROUND AN UPR HIGH... LIKELY TO TAKE THE FORM OF A CLOSED LOW AS PER OPERATIONAL SOLNS... MAY BRUSH THE NWRN MAINLAND AND THEN SETTLE OVER OR NEAR THE BERING SEA. THIS FEATURE IS EXPECTED TO BECOME MORE DOMINANT WITH TIME RELATIVE TO THE INITIAL BERING SEA SYSTEM... AND SHOULD HELP TO MAINTAIN THE DOWNSTREAM MEAN RIDGE NEAR ITS MIDWEEK POSN. AFTER EARLY DAY 5 WED THE PRECISE TRACK/FORM OF ENERGY REACHING THE NRN BERING SEA VICINITY AS WELL AS DETAILS OF PROGRESSIVE AND LOW AMPLITUDE FLOW ACROSS THE PAC WILL INFLUENCE THE TRACK/TIMING/STRENGTH OF THE INITIAL BERING SEA SYSTEM... AND OF COURSE PAC FLOW DETAILS WILL DETERMINE SPECIFICS OF ANY PSBL UPSTREAM WAVES. FCST DIFFICULTIES AT THE SFC ARE REFLECTED IN THE COMBINED GEFS/ECMWF/CMC 00Z ENSEMBLE LOW PLOTS. BY LATE THU THERE IS A NEARLY EVEN DISTRIBUTION OF PSBL SFC LOWS FROM THE EXTREME WRN PAC BTWN 35-55N LATITUDE TO THE ERN BERING SEA AND S OF THE MAINLAND BTWN 45-60N LATITUDE. FOR THE INITIAL BERING SEA LOW PREFER A TRACK CLOSE TO CONTINUITY BRINGING IT NEAR KODIAK ISLAND. OVER THE PAST DAY THE FARTHER SWD TRACK OF RECENT ECMWF RUNS HAS HAD SUPPORT FROM ISOLD RUNS OF OTHER MDLS THOUGH THE 00Z RUN IS A LITTLE NWD OF PRIOR RUNS. THE 12Z GFS PARALLEL AND UKMET GO ALONG WITH THIS SRN ROUTE. WOULD LIKE TO SEE SOME TRENDING IN THE ENSEMBLE MEANS BEFORE GRAVITATING TO THAT ALTERNATE SCENARIO. AT THE VERY LEAST THE STRENGTH/PERSISTENCE OF THE DOWNSTREAM RIDGE ALOFT SHOULD TEND TO PLACE LOWER PROBABILITY ON ANY SOLNS FOR THIS SYSTEM OR OTHER WAVES WITH A TRACK ON THE SERN SIDE OF THE SPREAD ONCE REACHING THE NERN PAC. MEANWHILE ENERGY SETTLING OVER THE BERING SEA MAY HAVE A TENDENCY TO LOWER SFC PRESSURES IN ITS VICINITY BY THE LATTER HALF OF THE PERIOD BUT SO FAR THE FULL ARRAY OF GUIDANCE DOES NOT OFFER ENOUGH CONFIDENCE FOR THE PLACEMENT OF A WELL DEFINED SFC SYSTEM. OVERALL PREFER A DAYS 4-8 TUE-SAT APPROACH THAT EMPHASIZES CONTINUITY AND MAJORITY CLUSTERING WITH A REFLECTION OF AGREEABLE OPERATIONAL DETAIL EARLY AND LARGE SCALE PATTERN OF THE ENSEMBLE MEANS LATE. TUE INTO EARLY WED INCORPORATE A BLEND OF 00Z ECMWF AND 00Z-06Z GFS/00Z GFS PARALLEL TO MAINTAIN DETAIL FOR THE INITIAL BERING SEA SYSTEM AND HIGH LATITUDE ENERGY THAT THE MDLS SAY SHOULD BE MORE CLOSED THAN FCST BY THE ENSEMBLE MEANS. ENOUGH SPREAD DEVELOPS TO FAVOR ADDING SOME COMPONENT OF THE 06Z GEFS/00Z ECMWF MEANS TO THE OPERATIONAL CLUSTER LATE WED THROUGH FRI. PREFER AN EVEN BLEND OF THE ENSEMBLE MEANS EXCLUSIVELY BY NEXT SAT THOUGH A LITTLE MANUAL ENHANCEMENT WAS NEEDED TO IMPROVE DETAIL AT THE SFC. THE RESULTING FCST BY NEXT SAT REPRESENTS A GOOD COMPROMISE AMONG VARIED SOLNS OF THE LAST FOUR 12-HRLY GEFS/ECMWF MEAN RUNS. RAUSCH