ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 133 PM EST FRI JAN 22 2016 VALID 12Z TUE JAN 26 2016 - 12Z SAT JAN 30 2016 MODEL/ENSEMBLE GUIDANCE CONTINUES TO SHOW GOOD LARGE SCALE AGREEMENT AND CONTINUITY FOR SIGNIFICANT FEATURES... WITH ONGOING UNCERTAINTIES REGARDING SOME SMALLER SCALE DETAILS. FOR THE SHORT RANGE SYSTEM REACHING THE SERN BERING SEA/SWRN COAST OF THE MAINLAND BY 12Z DAY 4 TUE THE 06Z GFS IS ON THE NRN SIDE OF THE GUIDANCE SPREAD. THE 00Z GFS/ECMWF ARE MORE REPRESENTATIVE OF THE MAJORITY CLUSTER. THEN ADJUSTMENTS ARE MINIMAL WITH THE STRONG MID-LATITUDE PACIFIC SYSTEM FCST TO TURN NWD ALONG 160-150W AND THEN NW ACROSS THE ALASKA PENINSULA AROUND THU. INDIVIDUAL MODEL RUNS HAVE BEEN SHOWING SOME DETAIL DIFFS... FAVORING PARTIAL INCLUSION OF THE ENSEMBLE MEANS. MEANWHILE TO THE E MODELS/ENSEMBLE MEMBERS STILL INDICATE POTENTIAL FOR ONE OR MORE NERN PAC WAVES TO REACH THE SRN COAST OF THE MAINLAND OR PANHANDLE. THERE IS STILL CONSIDERABLE SPREAD IN TRACK AND TIMING THUS KEEPING CONFIDENCE BELOW AVG FOR THAT ASPECT OF THE FCST. ENSEMBLE MEANS REMAIN FAIRLY CONSISTENT WITH THE EVOLUTION OF UPSTREAM LOW PRES FCST TO TRACK NEAR THE WRN HALF OF THE ALEUTIANS THU-SAT. OPERATIONAL RUNS HAVE BEEN SIGNALING THE EXISTENCE OF ONE OR MORE SFC LOWS BUT WITH CONSIDERABLE VARIABILITY IN THE DETAILS... FAVORING GREATER EMPHASIS ON THE ENSEMBLE MEANS FOR THIS SYSTEM UNTIL BETTER OPERATIONAL AGREEMENT EMERGES. MOST GUIDANCE IS SUGGESTING THAT THE PATTERN OVER/NEAR THE MAINLAND WILL EXPERIENCE A TRANSITION DURING THE LATTER HALF OF THE PERIOD AS THE AK PENINSULA SYSTEM WEAKENS AND THE WRN ALEUTIANS SYSTEM BECOMES MORE DOMINANT. THIS WOULD LEAD TO STRENGTHENING OF A NERN PAC/MAINLAND RIDGE VS THE WRN CANADA TO NORTH OF THE MAINLAND RIDGE FCST TO BE IN PLACE INTO THU-FRI. AS THIS TRANSITION OCCURS GUIDANCE SUGGESTS A PERIOD OF HIGHER DETAIL UNCERTAINTY OVER PORTIONS OF THE MAINLAND/NERN PAC. BASED ON PREFS FOR GREATER OPERATIONAL MODEL DETAIL EARLY IN THE FCST AND MORE CONSOLIDATED ENSEMBLE MEAN GUIDANCE FARTHER OUT IN TIME... PLUS DAMPENING OF LOWER CONFIDENCE NERN PAC WAVES... TODAY'S FCST STARTS WITH A BLEND OF 00Z GFS/ECMWF RUNS AND 06Z GEFS/00Z ECMWF MEANS. OPERATIONAL MODEL WEIGHTING STARTS AT ABOUT 70 PCT ON DAY 4 TUE... THEN DECREASES TO 40 PCT BY DAY 6 THU WITH ENSEMBLE MEANS USED EXCLUSIVELY FROM 00Z NEXT SAT ONWARD. RAUSCH