Prognostic Meteorological Discussion
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FXAK02 KWNH 111806
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 PM EDT FRI JUL 11 2014

VALID 12Z TUE JUL 15 2014 - 12Z SAT JUL 19 2014

TRENDS FROM 24 HRS AGO SHOW SOMEWHAT HIGHER HGTS BUILDING INTO THE
NERN PAC AND THUS GREATER POTENTIAL FOR CONSOLIDATION OF SEPARATE
PIECES OF NRN PAC ENERGY... WHILE A STRONGER RETROGRADING RIDGE
OVER THE BERING SEA AS OF TUE SEEMS TO BE SUPPRESSING THE NRN SIDE
OF THE ENVELOPE FOR NRN PAC SFC LOW PRESSURE EARLY IN THE PERIOD.
HOWEVER GUIDANCE SUGGESTS ONCE THIS RIDGE REACHES FARTHER WWD THE
STRONGER TREND MAY SUPPORT MORE INTERACTION BETWEEN A MEAN TROUGH
DEVELOPING JUST W OF THE MAINLAND AND THE NRN PAC SYSTEM...
ULTIMATELY LEADING TO A FARTHER NWD TRACK IN THE SECOND HALF OF
THE PERIOD.

THE PAST TWO ECMWF RUNS ARE AT ODDS WITH MOST OTHER SOLNS FOR THE
NRN PAC SYSTEM... BRINGING THE FEATURE INTO THE NERN PAC WHERE
CONSENSUS IS CURRENTLY EXPECTING A DEEP LAYER RIDGE.  THE 00Z
ECMWF MEAN IS MUCH CLOSER TO THE MAJORITY WITH A SFC LOW TRACK
THROUGH THE SERN BERING SEA ALBEIT WITH A MODEST WEAKNESS
EXTENDING EWD JUST S OF THE GULF OF ALASKA.  COMPARING REMAINING
GUIDANCE IN THE FIRST HALF OF THE PERIOD... OPERATIONAL RUNS
CLUSTER IN THE NERN PART OF THE BROADER AREA OF NRN PAC SFC LOW
PRESSURE SHOWN IN THE ENSEMBLE MEANS SO PREFER A COMPROMISE
BETWEEN THE OPERATIONAL AND ENSMEAN SOLNS.

BESIDES PSBLY INTERACTING WITH THE NRN PAC SYSTEM... THE MEAN
TROUGH DEVELOPING TO THE W OF THE MAINLAND SHOULD SUPPORT A
LEADING FRONTAL BNDRY THAT MAY BE WAVY AND SLOW MOVING TO STNRY
DEPENDING ON SHRTWV DETAILS.  AS WITH THE EVOLUTION TO THE S... A
COMPROMISE BETWEEN MODEL AND ENSEMBLE MEAN SOLNS APPEARS BEST FOR
RESOLVING UNCERTAIN DETAILS SFC/ALOFT OVER THE NRN MAINLAND.

THROUGH DAY 7 FRI THE DESIRED OPERATIONAL MODEL/ENSEMBLE MEAN
COMPROMISE IS ACHIEVED THROUGH A BLEND OF THE 00Z-12Z GFS/00Z
ECMWF AND 06Z GEFS/00Z ECMWF MEANS... REMOVING THE 00Z ECMWF AFTER
DAY 5 WED.  OPERATIONAL MODELS STILL FIT WITHIN THE BROAD SCALE
ENSEMBLE MEAN PATTERN BY DAY 8 SAT BUT DEPTH/DETAILS BECOME
SUFFICIENTLY UNCERTAIN TO GIVE PRIMARY WEIGHTING TO THE ENSEMBLE
MEANS AT THAT TIME.

RAUSCH

$$





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