ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 243 PM EDT MON MAY 01 2017 VALID 12Z FRI MAY 05 2017 - 12Z TUE MAY 09 2017 THE BIG PICTURE (NORTH PACIFIC INTO NORTH AMERICA) SHOWS ABOVE AVERAGE PREDICTABILITY IN THE LONGWAVE PATTERN IN THE MEDIUM RANGE. A DISTINCT WAVENUMBER 6 PATTERN IS EVIDENT OVER THE HEMISPHERE, WITH ONE OF THOSE TRAVERSING JUST SOUTH OF THE ALEUTIANS FRI THROUGH THE WEEKEND INTO EARLY NEXT WEEK. THE MODELS/ENSEMBLES HAVE BEEN RATHER STEADY, WITH EXPECTED DIFFERENCES IN THE DETAILS OF THE EVOLUTION OF THE SYSTEM. THIS INCLUDES SFC WAVE DEVELOPMENT AND PARENT LOW SHIFTING. OVERALL, STAYED WITH THE GUIDANCE THAT WAS CLOSEST TO THE ENSEMBLE MEANS (GEFS MEAN AND ECMWF ENSEMBLE MEAN) WHICH WAS MOSTLY THE 00Z ECMWF AND 12Z GFS. TREND HAS BEEN A SLIGHT SHIFT NORTHWARD IN THE TRACK OF THE UPPER/SFC LOW THIS WEEKEND, THOUGH WAS HESITANT TO PUSH ANY DISCERNIBLE SFC LOW ACROSS THE ALEUTIANS (ECMWF/UKMET/CANADIAN) JUST YET. ENSEMBLE LOW PLOTS SHOW ONLY ABOUT 10% OF THE MEMBERS WITH SFC LOWS NORTH OF THE ALEUTIANS. LATER IN THE PERIOD, THE GFS REMAINS SLOWEST AND FARTHEST SOUTH WITH THE UPPER LOW, ALLOWING MORE TROUGHING TO SETTLE INTO THE NORTH SLOPE. ENSEMBLES SUGGEST OTHERWISE, AND MAINTAINED RIDGING FROM NW CANADA THROUGH THE INTERIOR NEXT MON/TUE, KEEPING TROUGHING NORTH OF 70N. FRACASSO