Prognostic Meteorological Discussion
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FXAK02 KWNH 281847
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 PM EST FRI NOV 28 2014

VALID 12Z TUE DEC 02 2014 - 12Z SAT DEC 06 2014

THERE IS DECENT AGREEMENT AMONG GUIDANCE IN THE LARGE SCALE
PATTERN BUT A NUMBER OF IMPORTANT MEDIUM TO SMALLER SCALE DETAIL
ISSUES MAY TAKE A WHILE TO RESOLVE SATISFACTORILY.

A MEAN RIDGE IS FCST TO BECOME ESTABLISHED OVER EXTREME WRN CANADA
AND EXTEND INTO THE SERN MAINLAND AHEAD OF AN UPR LOW ASSOC WITH A
FAIRLY DEEP SYSTEM OVER THE BERING SEA EARLY IN THE WEEK.
MEANWHILE ENERGY FLOWING AROUND AN UPR HIGH... LIKELY TO TAKE THE
FORM OF A CLOSED LOW AS PER OPERATIONAL SOLNS... MAY BRUSH THE
NWRN MAINLAND AND THEN SETTLE OVER OR NEAR THE BERING SEA.  THIS
FEATURE IS EXPECTED TO BECOME MORE DOMINANT WITH TIME RELATIVE TO
THE INITIAL BERING SEA SYSTEM... AND SHOULD HELP TO MAINTAIN THE
DOWNSTREAM MEAN RIDGE NEAR ITS MIDWEEK POSN.

AFTER EARLY DAY 5 WED THE PRECISE TRACK/FORM OF ENERGY REACHING
THE NRN BERING SEA VICINITY AS WELL AS DETAILS OF PROGRESSIVE AND
LOW AMPLITUDE FLOW ACROSS THE PAC WILL INFLUENCE THE
TRACK/TIMING/STRENGTH OF THE INITIAL BERING SEA SYSTEM... AND OF
COURSE PAC FLOW DETAILS WILL DETERMINE SPECIFICS OF ANY PSBL
UPSTREAM WAVES.  FCST DIFFICULTIES AT THE SFC ARE REFLECTED IN THE
COMBINED GEFS/ECMWF/CMC 00Z ENSEMBLE LOW PLOTS.  BY LATE THU THERE
IS A NEARLY EVEN DISTRIBUTION OF PSBL SFC LOWS FROM THE EXTREME
WRN PAC BTWN 35-55N LATITUDE TO THE ERN BERING SEA AND S OF THE
MAINLAND BTWN 45-60N LATITUDE.  FOR THE INITIAL BERING SEA LOW
PREFER A TRACK CLOSE TO CONTINUITY BRINGING IT NEAR KODIAK ISLAND.
 OVER THE PAST DAY THE FARTHER SWD TRACK OF RECENT ECMWF RUNS HAS
HAD SUPPORT FROM ISOLD RUNS OF OTHER MDLS THOUGH THE 00Z RUN IS A
LITTLE NWD OF PRIOR RUNS.  THE 12Z GFS PARALLEL AND UKMET GO ALONG
WITH THIS SRN ROUTE.  WOULD LIKE TO SEE SOME TRENDING IN THE
ENSEMBLE MEANS BEFORE GRAVITATING TO THAT ALTERNATE SCENARIO.  AT
THE VERY LEAST THE STRENGTH/PERSISTENCE OF THE DOWNSTREAM RIDGE
ALOFT SHOULD TEND TO PLACE LOWER PROBABILITY ON ANY SOLNS FOR THIS
SYSTEM OR OTHER WAVES WITH A TRACK ON THE SERN SIDE OF THE SPREAD
ONCE REACHING THE NERN PAC.  MEANWHILE ENERGY SETTLING OVER THE
BERING SEA MAY HAVE A TENDENCY TO LOWER SFC PRESSURES IN ITS
VICINITY BY THE LATTER HALF OF THE PERIOD BUT SO FAR THE FULL
ARRAY OF GUIDANCE DOES NOT OFFER ENOUGH CONFIDENCE FOR THE
PLACEMENT OF A WELL DEFINED SFC SYSTEM.

OVERALL PREFER A DAYS 4-8 TUE-SAT APPROACH THAT EMPHASIZES
CONTINUITY AND MAJORITY CLUSTERING WITH A REFLECTION OF AGREEABLE
OPERATIONAL DETAIL EARLY AND LARGE SCALE PATTERN OF THE ENSEMBLE
MEANS LATE.  TUE INTO EARLY WED INCORPORATE A BLEND OF 00Z ECMWF
AND 00Z-06Z GFS/00Z GFS PARALLEL TO MAINTAIN DETAIL FOR THE
INITIAL BERING SEA SYSTEM AND HIGH LATITUDE ENERGY THAT THE MDLS
SAY SHOULD BE MORE CLOSED THAN FCST BY THE ENSEMBLE MEANS.  ENOUGH
SPREAD DEVELOPS TO FAVOR ADDING SOME COMPONENT OF THE 06Z GEFS/00Z
ECMWF MEANS TO THE OPERATIONAL CLUSTER LATE WED THROUGH FRI.
PREFER AN EVEN BLEND OF THE ENSEMBLE MEANS EXCLUSIVELY BY NEXT SAT
THOUGH A LITTLE MANUAL ENHANCEMENT WAS NEEDED TO IMPROVE DETAIL AT
THE SFC.  THE RESULTING FCST BY NEXT SAT REPRESENTS A GOOD
COMPROMISE AMONG VARIED SOLNS OF THE LAST FOUR 12-HRLY GEFS/ECMWF
MEAN RUNS.

RAUSCH

$$




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