ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 146 PM EST SUN JAN 04 2015 VALID 12Z THU JAN 08 2015 - 12Z MON JAN 12 2015 LATEST MODELS AND ENSEMBLES MAINTAIN SOME DEGREE OF CONTINUITY IN THE GENERAL LARGE SCALE EVOLUTION BUT CONTINUE TO EXHIBIT SOME SPREAD AND DAY TO DAY CHANGES IN THE DETAILS. A RIDGE OVER THE MAINLAND AS OF EARLY DAY 4 THU... LIKELY WITH AN EMBEDDED PIECE OF SHEARED MID LVL ENERGY... WILL WEAKEN AND SINK SEWD WHILE ANOTHER RIDGE BUILDS OVER ERN SIBERIA. AT THE START OF THE FCST LATEST GUIDANCE SHOWS A STRONGER TREND WITH THIS RIDGE VERSUS EARLIER RUNS. AS INDICATED BY MOST SOLNS YDAY THERE IS STILL A MAJORITY CLUSTER THAT SHOWS A COMPACT UPR LOW OVER THE SRN BERING SEA. HOWEVER THERE REMAINS POOR AGREEMENT OVER ITS DEPTH/ASSOC SFC REFLECTION AS WELL AS WITH THE ULTIMATE TRACK AFTER THU. LINGERING POTENTIAL ALSO EXISTS FOR SOME INTERACTION WITH PACIFIC ENERGY. THERE ARE FEW OPTIMAL OPERATIONAL SOLNS WITH THE 00Z GFS/PARALLEL GFS ON THE NRN SIDE OF THE SPECTRUM WITH THE COMPACT UPR LOW AND THE 06Z GFS-P MORE SHEARED THAN THE MAJORITY CLUSTER... WHILE THE 00Z ECMWF MAY BE TOO STRONG SFC/ALOFT AND THE 06Z GFS A TAD WEAK/SWD. AT THE SAME TIME THERE IS FAIR CONTINUITY WITH THE IDEA OF NERN PAC SFC LOW PRESSURE TRACKING NWWD AND BRUSHING KODIAK ISLAND AND THE PENINSULA DURING THE FIRST HALF OF THE PERIOD. AN AVERAGE AMONG THE 00Z ECMWF-CMC/06Z GFS/00Z ECMWF MEAN LOOKS BEST FOR THIS FEATURE. ACCOUNTING FOR BOTH FEATURES YIELDS A PREFERENCE FOR A NEARLY EVEN BLEND OF THE 00Z ECMWF/00Z ECMWF MEAN/06Z GFS FROM DAY 4 THU INTO EARLY DAY 6 SAT. FARTHER NWD THIS BLEND PROVIDES A GOOD INTERMEDIATE SOLN FOR SHALLOW TROUGHING ALOFT AND SFC HIGH PRESSURE EDGING INTO THE NRN MAINLAND. AFTER EARLY SAT GUIDANCE AGREES UPON EWD PROGRESSION OF AN AXIS OF LOW HGTS ALOFT... LIKELY CONTAINING ONE OR MORE UPR LOWS... TO THE S OF THE ALEUTIANS. ENSEMBLE MEAN AGREEMENT AND CONTINUITY OVER THE PAST 24 HRS HAVE BEEN GOOD ASIDE FROM TYPICAL RUN TO RUN VARIATIONS. AS WAS THE CASE YDAY THE 06Z GEFS MEAN IS A LITTLE DEEPER THAN THE 00Z ECMWF MEAN WITH THE SFC LOW TRACKING S OF THE ALEUTIANS. DURING THE LATTER HALF OF THE PERIOD THE OPERATIONAL MODELS BECOME TOO DIVERGENT IN THEIR SFC LOW SOLNS TO USE ANY SPECIFIC RUN OF MODEL OUTPUT... SO PREFER A 06Z GEFS/00Z ECMWF MEAN BLEND WITH A SLIGHT LEAN TO THE GEFS FOR ITS DEPTH. THIS SOLN PROVIDES A REASONABLE FCST FARTHER N WITH NRN MAINLAND TROUGHING ALOFT PSBLY ERODING IN FAVOR OF A BC COAST INTO MAINLAND RIDGE DAY 8 MON IN RESPONSE TO THE LOW HGTS BECOMING ESTABLISHED OVER THE CNTRL PAC. ECMWF RUNS HAVE BEEN TRYING TO TREND AWAY FROM ITS DEEPER TROUGHING OVER THE MAINLAND LATE IN THE FCST PERIOD. MEANWHILE THERE ARE INDICATIONS THAT A SFC WAVE COULD REACH THE EXTREME NERN PAC NEXT WEEKEND. THE ENSMEAN PREF MAINTAINS REASONABLE CONTINUITY WITH A WEAK SFC LOW/FRONT SE OF KODIAK ISLAND AS OF 12Z SAT WEAKENING TO A SFC TROUGH NEARING THE SRN COAST/PANHANDLE ON SUN. RAUSCH