ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 217 PM EDT THU APR 16 2015 VALID 12Z MON APR 20 2015 - 12Z FRI APR 24 2015 OVERALL THERE IS BETTER THAN AVERAGE AGREEMENT AND CONTINUITY REGARDING EXPECTED LARGE SCALE FLOW... WITH A MEAN TROUGH POSITIONED JUST W OF THE MAINLAND AND MEAN RIDGE OVER WRN CANADA. MOST SOLNS INDICATE AN UPR LOW CENTER SHOULD BE EMBEDDED WITHIN THE MEAN TROUGH FOR A DECENT PORTION OF THE PERIOD WHILE A COUPLE BUNDLES OF ENERGY CARRIED ALONG IN PACIFIC FLOW MAY ADD SOME UNCERTAINTY IN TERMS OF TIMING/DETAIL OF INDIVIDUAL SYSTEMS. FOR DAYS 4-5 MON-TUE AN AVG OF THE 00Z ECMWF AND 00Z/06Z GFS PROVIDES A GOOD REPRESENTATION OF CONSENSUS AND OPERATIONAL DETAIL FOR THE WEAKENING SYSTEM OFF THE WRN COAST OF THE MAINLAND AND FOR THE SFC FRONT INITIALLY NEAR THE NRN COAST. AFTER TUE... GUIDANCE DIVERGES ON THE TRACK OF NRN PAC LOW PRES THAT SHOULD REACH A POSN SW OF THE PENINSULA BY 12Z WED. CURRENTLY THE 00Z/06Z GFS IDEA OF WRAPPING THE SFC LOW INTO THE BERING SEA IS SUPPORTED BY ONLY A MINORITY OF 00Z GEFS/ECMWF/CMC ENSEMBLE MEMBERS SO IT SEEMS REASONABLE TO EXCLUDE THOSE GFS RUNS FROM THE FCST BLEND FROM 12Z WED ONWARD. THE 12Z GFS HAS FAVORABLY TRENDED MORE SUPPRESSED THOUGH STILL PULLS UP A NRN SFC LOW BY LATE THU-FRI. MEANWHILE THERE ARE DECENT INDICATIONS THAT ANOTHER SYSTEM SHOULD REACH A POSN TO THE SW OF THE PENINSULA BY LATE NEXT WEEK BUT AT THE MOMENT IT IS NOT TOO CLEAR WHAT THE RELATIVE CONTRIBUTIONS WILL BE FROM ENERGY/LOW PRES CROSSING THE EXTREME NRN PAC/ALEUTIANS VERSUS THE MID-LATITUDE PAC. AN AVG OF THE 00Z ECMWF/ECMWF MEAN AND 00Z NAEFS/06Z GEFS MEANS PROVIDES A GOOD INTERMEDIATE TRACK FOR THIS SYSTEM IN LIGHT OF THE CURRENT UNCERTAINTY IN DETAILS. THE COMBINATION OF THESE SYSTEMS SHOULD LEAD TO A COUPLE PERIODS OF ENHANCED SFC GRADIENT ALONG THE PENINSULA/SWRN COAST. RAUSCH