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000
FXAK02 KWNH 201806
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 PM EDT MON MAY 20 2013

VALID 12Z FRI MAY 24 2013 - 12Z TUE MAY 28 2013

MEDIUM RANGE GUIDANCE IS SHOWING IMPROVED CONVERGENCE WITH RESPECT
TO THE FCST DEVELOPMENT OF CNTRL PACIFIC LOW PRESSURE AND ASSOC
CLOSED LOW ALOFT THAT SHOULD TRACK INTO THE ALEUTIANS/BERING SEA
DURING THE PERIOD.  THIS LEADS TO HIGHER CONFIDENCE IN THE OVERALL
FCST COMPARED TO 24 HRS AGO WHEN THE 00Z/19 ENSEMBLE RUNS MADE A
SIGNIFICANT ADJUSTMENT TOWARD THE CURRENTLY ACCEPTED SCENARIO.
DOWNSTREAM FROM THIS SYSTEM THERE IS REASONABLE AGREEMENT THAT A
RIDGE ALOFT BUILDING INTO THE NERN PAC/MAINLAND ALASKA EARLY IN
THE PERIOD WILL CONNECT WITH THE RIDGE INITIALLY OVER WRN
CANADA... YIELDING A MEAN RIDGE EXTENDING NWWD FROM WRN CANADA BY
THE LATTER HALF OF THE FCST.  AT THE SFC THE CONSENSUS FCST
INDICATES A PERSISTENT CNTRL MAINLAND TROUGH BETWEEN A NARROW
RIDGE OVER THE EXTREME NERN PAC AND ANOTHER RIDGE ALONG/N OF 70N
LATITUDE.

IN THE DAYS 4-6 FRI-SUN TIME FRAME A COMPROMISE AMONG THE 12Z
GFS/00Z ECMWF AND 00Z ECMWF/NAEFS MEANS OFFERS A GOOD INTERMEDIATE
SOLN FOR THE SYSTEM EVOLVING OVER THE NRN PAC/ALEUTIANS/BERING
SEA... WHILE LEANING AWAY FROM THE 06Z GFS/GEFS MEAN WHICH
SUPPRESS THE RIDGE ALOFT OVER THE MAINLAND RELATIVE TO OTHER
GUIDANCE.  INTERESTINGLY THE 00Z-12Z/19 RUNS OF THE ECMWF ALSO
SUPPRESSED THE RIDGE BEFORE THE 00Z/20 RUN ADJUSTED TO CONSENSUS.
DAYS 7-8 MON-TUE FAVOR THE 00Z ECMWF MEAN AS THE STARTING POINT
FOR THE FCST DUE TO NAEFS/GEFS MEANS BECOMING SLIGHTLY
FASTER/WEAKER WITH THE ALEUTIANS/BERING SEA SYSTEM AND TYPICALLY
LOWER CONFIDENCE IN OPERATIONAL MODEL DETAILS BY THAT TIME FRAME.

RAUSCH

$$