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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1926Z Sep 23, 2014)
 
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Abbreviations and acronyms used in this product
 
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
326 PM EDT TUE SEP 23 2014

VALID 12Z SAT SEP 27 2014 - 12Z WED OCT 01 2014

TO BEGIN THE PERIOD ON SATURDAY MORNING...A HIGH AMPLITUDE PATTERN
WILL BE IN PLACE WITH AN UPPER RIDGE CENTERED OVER THE WESTERN
ALEUTIANS WHILE A PAIR OF TROFS ANCHOR THE REGION TO THE WEST AND
EAST...RESPECTIVELY. THE PATTERN IS FORECAST TO BE PROGRESSIVE AS
THE LEAD SYSTEM DROPS DOWN FROM THE GULF OF AK INTO THE NORTHEAST
PACIFIC. IN ITS WAKE...HEIGHTS WILL BEGIN TO BUILD OVER CENTRAL AK
AS AN UPSTREAM SYSTEM DIGS TOWARD 50N/170W. THE OVERALL MODEL
AGREEMENT WAS REASONABLE FOR DAYS 4/5 WITH THE EXCEPTION OF THE
00Z UKMET WHICH OVERDEVELOPS A SURFACE LOW INTENSIFYING ACROSS THE
GULF OF AK. THE 12Z GFS/00Z ECMWF WERE APPLIED TO THE FORECAST
BLEND FOR DAYS 4/5 WITH A LITTLE MORE EMPHASIS ON THE DEEPER ECMWF
SOLUTION. MULTI-DAY TRENDS SUGGESTED THE GFS SUITE WAS PERHAPS A
TAD WEAK SO EMPHASIZED THE STRONGER ECMWF. BY DAY 6...THE 12Z
GFS/06Z GEFS MEAN WERE A BIT QUICKER CARRYING THE UPPER TROF DOWN
INTO THE NORTHEAST PACIFIC RELATIVE TO THE SLOWER 00Z ECMWF
ENSEMBLE/CMC/NAEFS MEANS. FARTHER UPSTREAM...MODEL CONSISTENCY HAS
BEEN POOR WITH HOW THEY CARRY THE NEXT UPPER TROF. PREVIOUS MODEL
CYCLES DE-EMPHASIZED THE BUILDING RIDGE ACROSS CENTRAL AK WHILE
THE MOST RECENT RUNS APPEAR TO HAVE CAUGHT ON WITH THE TREND OF
BUILDING A RATHER PRONOUNCED MID-LEVEL RIDGE. THIS AMPLIFIED
PATTERN IS SUPPORTED BY THE ENSEMBLE MEANS ALONG WITH A VAST
MAJORITY OF THE INDIVIDUAL MEMBERS IN THE SPAGHETTI PLOT. FOR DAYS
6-8...LEANED MORE HEAVILY ON THE ENSEMBLE MEANS GIVEN THE POOR
RUN-TO-RUN CONTINUITY IN THE DETERMINISTIC GUIDANCE. WPC FAVORED
AN EQUAL BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE MEAN WITH
CONFIDENCE BEING SLIGHTLY ABOVE NORMAL.


RUBIN-OSTER