Prognostic Meteorological Discussion
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FXAK02 KWNH 221801
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EDT TUE APR 22 2014

VALID 12Z SAT APR 26 2014 - 12Z WED APR 30 2014

MOST GUIDANCE EXPECTS AN ELONGATED AREA OF LOWER HGTS ALOFT...
EXTENDING FROM THE SRN BERING SEA E/SEWD AS OF EARLY SAT... TO
CONSOLIDATE INTO A MEAN CLOSED LOW THAT SHOULD LINGER OVER THE
NERN PAC FOR MOST OF THE PERIOD.  SOLNS DIFFER A LITTLE MORE WITH
THE PATTERN OVER THE MAINLAND WITH A MODERATE MAJORITY SHOWING
MODEST RIDGING EXTENDING INTO THE MAINLAND FROM NWRN CANADA VERSUS
GFS/GEFS MEAN RUNS THAT MAINTAIN MORE OF A WEAKNESS ALOFT.  SFC
LOW CLUSTERING FROM THE ERN ALEUTIANS/PENINSULA INTO THE NERN PAC
IS NOT YET AS GOOD AS DESIRED.  ON DAY 4 SAT THE 00Z ECMWF/CMC ARE
WELL WWD OF THE 00Z/06Z/12Z GFS AND 00Z/06Z GEFS MEAN WITH SFC LOW
PRESSURE BUT THE 00Z CMC MEAN IS EVEN FARTHER WWD.  THUS FAR THERE
IS NOT ENOUGH CONTINUITY TO GO WITH THE FARTHEST WWD SOLNS... BUT
THE 00Z ECMWF MEAN HAS MADE A DECENT NWWD ADJUSTMENT SINCE PRIOR
RUNS AND PROVIDES A GOOD STARTING POINT IN LIGHT OF CURRENT
SPREAD.  THE NEXT UNCERTAINTY IS THE ULTIMATE EVOLUTION OF NRN PAC
ENERGY THAT FLOWS AROUND THE SRN/ERN PERIPHERY OF THE NERN PAC UPR
LOW.  RECENT OPERATIONAL MODEL RUNS SUGGEST POTENTIAL FOR THE
ENERGY ALOFT TO SUPPORT A COMPACT NWD MOVING SFC SYSTEM THAT COULD
BRUSH THE PANHANDLE AROUND DAYS 6-7 MON-TUE.  THIS IS A TRACKABLE
FEATURE ORIGINATING FROM THE SHORT RANGE SO ENHANCING AN INITIALLY
PREFERRED 00Z ECMWF ENSEMBLE MEAN FCST TO INCLUDE AT LEAST A WEAK
WAVE SEEMS REASONABLE.

UPSTREAM FOCUS WILL BE ON PSBL STREAM INTERACTION THAT MEDIUM
RANGE GUIDANCE TENDS TO HAVE DIFFICULTIES WITH... IN THIS CASE NRN
STREAM ENERGY TRACKING OUT OF ASIA AND ACROSS KAMCHATKA ALONG WITH
A SEPARATE SRN STREAM WRN PAC SYSTEM THAT BECOMES DETACHED FROM
THE WESTERLIES EARLY IN THE FCST.  CURRENTLY ECMWF/CMC MODEL AND
ENSEMBLE GUIDANCE AS A WHOLE COMPARES BETTER TO CONTINUITY IN
BEING LESS AMPLIFIED/MORE PROGRESSIVE WITH THE NRN STREAM SYSTEM
RELATIVE TO 00Z-06Z GFS/GEFS SOLNS.  IN SOME WAYS THE 12Z GFS
SHOWS SOME 00Z ECMWF-LIKE ADJUSTMENTS BUT CONFIDENCE IN DETAILS
REMAINS BELOW AVERAGE.  THE MAJORITY SCENARIO LEADS TO MORE
EMPHASIS ON BERING SEA SFC LOW PRESSURE VERSUS HAVING A SLOW
MOVING SYSTEM TO THE S OF THE WRN ALEUTIANS THROUGH NEXT TUE-WED.
THE 00Z ECMWF MEAN HAS SLOWED SOMEWHAT COMPARED TO PREVIOUS RUNS
SO IT PROVIDES A GOOD INTERMEDIATE SOLN BETWEEN THE FASTER 00Z
CMC/CMC MEAN AND LESS PROBABLE 00Z-06Z GFS/GEFS MEAN.

RAUSCH

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