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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1835Z Jan 21, 2015)
 
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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
135 PM EST WED JAN 21 2015

VALID 12Z SUN JAN 25 2015 - 12Z THU JAN 29 2015

GUIDANCE CONTINUES TO SHOW SIGNIFICANT DIFFS OVER THE MAINLAND. 
LATEST GFS/ECMWF/CMC RUNS BRING AN UPR LOW INITIALLY N OF 70N SWD
INTO THE NRN MAINLAND WHILE ENSEMBLE MEANS ARE FAIRLY CONSISTENT
AND AGREEABLE WITH EJECTING MOST OF THE UPR LOW ENERGY EWD AND
DEPICTING A STEADILY WEAKENING UPR TROUGH OVER THE MAINLAND. 
DEEPER ENSEMBLE MEAN TRENDS WITH THE UPR TROUGH HAVE BECOME LESS
PRONOUNCED COMPARED TO YDAY BUT ESPECIALLY EARLY-MID PERIOD THERE
REMAINS ROOM FOR A DEEPER FEATURE AS SUGGESTED BY MOST OPERATIONAL
SOLNS.  LATER IN THE PERIOD EXPECT RIDGING TO BUILD FROM EXTREME
WRN CANADA INTO THE SERN MAINLAND IN RESPONSE TO THE SYSTEM
TRACKING TO THE S OF THE ALEUTIANS.  THIS ASPECT OF THE FCST MAY
BE BETTER HANDLED BY THE ENSEMBLE MEANS.  AS FOR THE NRN PAC
SYSTEM ITSELF... MODEL/ENSEMBLE GUIDANCE MAINTAINS BETTER THAN AVG
CLUSTERING ASIDE FROM DIFFICULT TO RESOLVE SMALL SCALE DETAILS.

GIVEN POTENTIAL FOR OPERATIONAL RUNS TO HAVE A BETTER HANDLE ON
EARLY PERIOD EVOLUTION OVER THE MAINLAND AND GOOD AGREEMENT S OF
THE ALEUTIANS... DAYS 4-5 SUN-MON LEAN 2/3 TOWARD THE 12Z GFS/00Z
ECMWF VERSUS THE 00Z ECMWF/06Z GEFS MEANS.  DAY 6 USES AN EVENLY
WEIGHTED TRANSITION BEFORE GOING TO A 70/20/10 BLEND OF THE 00Z
ECMWF/00Z NAEFS/06Z GEFS MEANS WITH TYPICAL DECLINE IN CONFIDENCE
FOR OPERATIONAL MODEL DETAILS AT THAT TIME FRAME.

RAUSCH