Prognostic Meteorological Discussion
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FXAK02 KWNH 241901
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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


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