ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 300 PM EDT WED MAY 24 2017 VALID 12Z SUN MAY 28 2017 - 12Z THU JUN 01 2017 CONTINUE TO SEE SHIFTS IN THE GUIDANCE REGARDING THE ORIENTATION/EVOLUTION OF THE TROUGHING FROM THE BERING SEA ACROSS THE ALEUTIANS AND SOUTH OF THE AKPEN. DETERMINISTIC MODELS HAVE SHOWED LITTLE CONTINUITY WHILE THE ENSEMBLE MEANS APPEAR WASHED OUT BY NEXT WEEK. TREND HAS BEEN TOWARD A MORE DEFINED LEAD SYSTEM SOUTH OF THE ALEUTIANS SUN-TUE PER THE 06Z GFS AND 00Z ECMWF. ENSEMBLE MEANS HAVE ALSO FAVORED A FARTHER SOUTH SYSTEM THAT MAY LINGER AROUND 50-55N RATHER THAN MOVE NORTHWARD LIKE OLDER RUNS OR THE 12Z GFS. PREFER TO MAINTAIN A DUAL LOW/SYSTEM SETUP (THOUGH WITH THE EMPHASIS ON THE LEAD RATHER THAN TRAILING SYSTEM) SOMEWHAT LIKE THE 00Z GEFS MEAN. ECMWF ENSEMBLE MEAN AGAIN WASHED OUT THE PRESSURE PATTERN BETWEEN THE TWO LOWS, THOUGH THEY MAY COMBINE NEXT WEEK ANYWAY. USED A BLEND OF THE 06Z GFS WITH THE 00Z ECMWF AND THE 06-00Z GEFS MEANS TO MAINTAIN SOME STRUCTURE DESPITE THE LOW CONFIDENCE IN SUCH DETAILS. RIDGING APPEARS TO HOLD STRONG OVER WESTERN NORTH AMERICA INTO INTERIOR ALASKA WHICH WILL KEEP TROUGHING TO THE NORTHWEST NEAR WRANGEL ISLAND AND THROUGH THE BERING SEA. FRACASSO