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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1839Z Dec 16, 2014)
 
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
139 PM EST TUE DEC 16 2014

VALID 12Z SAT DEC 20 2014 - 12Z WED DEC 24 2014

MOST MODEL AND ENSEMBLE GUIDANCE SHOWS GOOD AGREEMENT IN THE LARGE
SCALE WITH AN UPR LOW INITIALLY NEAR/S OF THE ERN ALEUTIANS
TRACKING NEWD AND OPENING UP INTO A SHRTWV TROUGH WHILE UPSTREAM
FLOW STREAMS ALONG AHEAD OF A DEEP UPR LOW THAT IS CURRENTLY FCST
TO MOVE OVER KAMCHATKA.  HOWEVER WITHIN THIS CONSENSUS EVOLUTION
IN THE MEAN... THERE ARE ENOUGH DIFFS IN THE DETAILS AMONG
INDIVIDUAL MODELS AND FROM RUN TO RUN TO MAKE IT DIFFICULT TO
INCORPORATE MUCH OPERATIONAL GUIDANCE ESPECIALLY OVER THE NERN
PACIFIC.

ALREADY AT THE START OF THE PERIOD ON SAT THERE ARE MEANINGFUL
DIFFS WITH ONE OR MORE PIECES OF ENERGY WITHIN OR ON THE SRN/ERN
SIDE OF THE MEAN CLOSED LOW ALOFT NEAR THE ERN ALEUTIANS.  AS A
RESULT THERE IS A SEEMINGLY RANDOM ARRAY OF SFC LOW SOLNS FROM S
OF THE ALEUTIANS INTO THE NERN PAC... BOTH IN OPERATIONAL RUNS AND
00Z GEFS/ECMWF/CMC ENSEMBLE MEMBERS.  TO START THE FCST ON DAY 4
SAT PREFER THE ENSEMBLE MEANS AND SOMEWHAT MORE THE 00Z
ECMWF/NAEFS MEANS AS THEY MAINTAIN MORE EVIDENCE OF A WRN SFC LOW
AS OF EARLY SAT WHICH BETTER FOLLOWS CONTINUITY.  THERE IS
SOMEWHAT IMPROVED CLUSTERING/CONTINUITY TOWARD CONSOLIDATION OF
LOW PRESSURE E/NE OF KODIAK ISLAND BY SUN-MON AS THE CORE OF
SUPPORTING DYNAMICS LIFTS SLOWLY NEWD... SO THE 06Z GEFS MEAN CAN
ALSO BE INCLUDED IN THE BLEND AFTER SAT.  LINGERING LOW PRESSURE
NEAR THE GULF OF ALASKA SHOULD DISSIPATE/DEPART AFTER EARLY TUE. 
FLOW AHEAD OF THE DEEP KAMCHATKA SYSTEM LATER IN THE PERIOD IS
FCST TO PUSH A FAST MOVING FRONTAL SYSTEM ACROSS THE BERING
SEA/ALEUTIANS DURING THE FIRST HALF OF NEXT WEEK.  SOME
OPERATIONAL MODEL RUNS ARE SHOWING POTENTIAL FOR A WRN BERING SEA
SFC LOW OF CONSIDERABLE DEPTH SO BY DAYS 7-8 TUE-WED IT WOULD BE
REASONABLE TO INCLUDE SOME OF THE DEEPER 06Z GEFS MEAN AND TO SOME
EXTENT 00Z NAEFS MEAN ALONG WITH THE 00Z ECMWF MEAN.  COMPARED TO
MOST OPERATIONAL/ENSEMBLE GUIDANCE... INCL PARALLEL GFS RUNS...
00Z/06Z/12Z GFS RUNS ARE FARTHER EWD WITH BERING SEA LOW PRESSURE.


RAUSCH