Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1
000
FXAK02 KWNH 231831
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
230 PM EDT SAT MAY 23 2015

VALID 12Z WED MAY 27 2015 - 12Z SUN MAY 31 2015

FOR THE MAINLAND AND PANHANDLE... ENERGY REACHING THE SRN COAST
LATE IN THE SHORT RANGE TIME FRAME HAS TRENDED MORE CLOSED IN
LATEST RUNS.  BY THE EXTENDED TIME FRAME IT BECOMES INCREASINGLY
DIFFICULT TO RESOLVE WHAT THIS FEATURE WILL DO AS IT ESSENTIALLY
BECOMES EMBEDDED WITHIN THE LARGE SCALE MEAN RIDGE.  SOLNS RANGE
FROM CONTINUED PROGRESSION IN THE 00Z ECMWF/CMC TO AN EVENTUAL
NWWD/WWD DRIFT IN RECENT GFS RUNS.  CURRENTLY FAVOR THE ENSEMBLE
MEANS TO YIELD A WEAKER SOLN GIVEN THE SURROUNDING MEAN RIDGE AND
CONSIDERABLE SPREAD.  REGARDING THE UPR RIDGE THE ENSEMBLE MEANS
HAVE GENERALLY BEEN MORE CONSISTENT/AGREEABLE RELATIVE TO
OPERATIONAL MODEL RUNS.  AS SPORADIC MODEL RUNS HAVE ADVERTISED
THOUGH... LATEST GEFS MEANS SHOW GREATER POTENTIAL THAN OTHER
MEANS FOR A CLOSED HIGH TO FORM DURING A PORTION OF THE PERIOD AND
WITH HIGHER HGTS.  GIVEN ENSMEAN TRENDS OVER THE PAST 36 HRS
TOWARD A STRONGER RIDGE IT SEEMS REASONABLE TO INCLUDE AT LEAST
SOME WEIGHTING OF THE 06Z GEFS MEAN AND COMPROMISE 00Z NAEFS MEAN
ALONG WITH THE 00Z ECMWF MEAN.  THERE IS MINIMAL SUPPORT FOR THE
00Z ECMWF THAT BRINGS SIGNIFICANT HGT FALLS/COMPACT CLOSED LOW
INTO THE MAINLAND FROM THE NORTHEAST NEXT WEEKEND.

MEANWHILE GUIDANCE CONTINUES TO BE CHALLENGED BY EVOLUTION ACROSS
THE BERING SEA/ALEUTIANS/NRN PACIFIC.  A RELATIVE CONSENSUS
APPEARS TO HAVE FORMED FOR THE LEADING BERING SEA SYSTEM THAT HAD
CONSIDERABLE SPREAD 24 HRS AGO... KEEPING THE SFC LOW ON THE WRN
SIDE OF THE PRIOR SOLN ENVELOPE.  MODELS/INDIVIDUAL ENSEMBLE
MEMBERS STILL VARY WIDELY FOR THE NRN PAC SYSTEM EXPECTED TO
APPROACH THE ALEUTIANS WED-THU.  00Z/06Z GFS RUNS ARE MORE SIMILAR
TO RUNS FROM 12-24 HRS EARLIER AS WELL AS PRIOR ECMWF RUNS IN
BRINGING THE SYSTEM INTO THE BERING SEA.  HOWEVER THERE IS A
NOTABLE SWD TREND IN LATEST GEFS/ECMWF MEANS AS WELL AS THE 00Z
ECMWF.  CMC RUNS HAVE BEEN S OF THE ALEUTIANS FOR AT LEAST THE
PAST 2-3 CYCLES.  CONFIDENCE REMAINS BELOW AVG BUT HINTS AT
FURTHER RETROGRESSION/WWD BUILDING OF THE MAINLAND RIDGE PLUS
SIGNIFICANT CHANGES IN THE 12Z GFS RUN/CONTINUITY IN THE CMC AT
LEAST PROVIDE ADDED SUPPORT FOR SOME SWD ADJUSTMENT FROM YDAYS
ENSMEAN CONSENSUS.

ACCOUNTING FOR THE ABOVE CONSIDERATIONS... THE FCST THROUGH THE
DAYS 4-8 WED-SUN PERIOD STARTS WITH A 60/20/20 BLEND OF THE 00Z
ECMWF MEAN/00Z NAEFS MEAN/06Z GEFS MEAN WITH MINOR ADJUSTMENTS AS
NEEDED.

RAUSCH

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.