Prognostic Meteorological Discussion
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FXAK02 KWNH 041834
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT FRI SEP 04 2015

VALID 12Z TUE SEP 08 2015 - 12Z SAT SEP 12 2015

OVER THE PAST DAY THERE HAS BEEN A NOTICEABLE TREND TOWARD GREATER
STRENGTH/INFLUENCE OF ENERGY WITHIN THE MAINLAND MEAN TROUGH
ALOFT.  THIS ADJUSTMENT IN THE GUIDANCE LEADS TO MORE SUPPRESSED
TRACKS FOR BOTH AN INITIAL SYSTEM FCST TO BE OVER THE BERING SEA
AS OF DAY 4 TUE AND AN UPSTREAM SYSTEM WHICH THE MAJORITY GUIDANCE
CLUSTER HAD TRACKED OVER THE ALEUTIANS/SRN BERING SEA BUT NOW IS
OVER THE NRN PAC.  AT LEAST THERE IS STILL A TENDENCY IN THE
ENSEMBLES TOWARD GENERAL LOW PRESSURE AT THE SFC BTWN THE AK
PENINSULA/KODIAK ISLAND AND THE SRN COAST OF THE MAINLAND.

FROM DAY 4 TUE INTO EARLY DAY 5 WED A MODEL/ENSEMBLE COMPROMISE
AMONG THE 06Z GFS/GEFS AND 00Z ECMWF/ECMWF MEAN PROVIDED A
REASONABLE INTERMEDIATE SOLN SFC/ALOFT AND ACCOUNTS FOR 1500 UTC
CPHC ADVISORY TRACK OF IGNACIO WHOSE EXTRATROPICAL EVOLUTION
SHOULD INFLUENCE AT MOST THE EXTREME SRN PART OF THE PANHANDLE.
MEANINGFUL MODEL/ENS SPREAD FOR TIMING OF IGNACIO PERSISTS BUT
OVER THE PAST DAY GUIDANCE HAS SETTLED INTO BETTER AGREEMENT FOR
LATITUDE OF THE TRACK.

THE REMAINDER OF THE PERIOD EMPHASIZES THE 06Z GEFS/00Z ECMWF
MEANS WITH 30 PCT INCLUSION OF THE 00Z ECMWF.  THE LATTER HELPS
MAINTAIN A REFLECTION OF THE POTENTIAL NRN PAC SYSTEM HEADING
TOWARD THE PENINSULA LATE IN THE PERIOD... WITH A GOOD COMPROMISE
BTWN YDAYS TRACK ACROSS THE SRN BERING SEA AND SOME OTHER SOLNS
INCL LATEST GFS RUNS THAT ARE EVEN FARTHER SWD AND SLOWER.  ALSO
NOTE THAT AROUND MID-PERIOD GFS RUNS ARE ON THE SRN SIDE OF THE
ENSEMBLE SPREAD FOR THE INITIAL BERING SEA SYSTEM THAT HEADS INTO
THE NRN THEN NERN PAC... ULTIMATELY LEADING TO MORE MSTR REACHING
THE SERN COAST/PANHANDLE THAN INDICATED BY CURRENT CONSENSUS.  THE
MEAN PATTERN DOES SEEM TO SUPPORT SOME ENHANCEMENT OF MSTR OVER
THAT REGION THOUGH.

RAUSCH

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