Prognostic Meteorological Discussion
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FXAK02 KWNH 291843
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT SUN MAR 29 2015

VALID 12Z THU APR 02 2015 - 12Z MON APR 06 2015

...PATTERN/SENSIBLE WEATHER HIGHLIGHTS...

ALASKAN MEDIUM-RANGE FLOW FEATURES A WELL ORGANIZED LOW THAT
TRACKS FROM THE NRN TO ERN GULF OF ALASKA THU-SAT. MODEL AND
ENSEMBLE FORECAST SPREAD HAS DECREASED FROM THE LAST FEW DAYS WITH
THIS FEATURE WHOSE ENSEMBLE LOW CLUSTERING IS NOW MUCH TIGHTER.
THIS ACTIVE LOW SHOULD FAVOR HIGH WIND/WAVES AND MODEST TO TERRAIN
ENHANCED LOCALLY HEAVIER PCPN POTENTIAL SPREADING FROM SRN THROUGH
SERN AK. THIS OCCURS UNDERNEATH GRADUALLY BUILDING INTERIOR AK
HIGH PRESSURE WITH ONLY SOME LIGHT NRN AK IMPULSE RELATED SNOW.
UPSTREAM...ADDITIONAL WELL ORGANIZED LOW DEVELOPMENT WORKS INTO
THE SRN BERING SEA JUST NORTH OF THE WRN TO CENTRAL ALEUTIANS
THU-NEXT MON. THIS SYSTEM HAS TRENDED SLOWER AND SLIGHTLY FURTHER
NORTH THAN YESTERDAY AND THAT SEEMS CONSISTENT WITH WATER VAPOR
LOOPS/OVERALL FLOW AMPLIFICATION. THE LOW AND SECONDARY WAVE
DEVELOPMENT TO THE SOUTH OF ALEUTIANS WILL FOCUS UNSETTLED SEAS
AND A MODEST BUT PROLONGED SWIRL OF WRAP-AROUND PCPN SPREADING
ACROSS THE EXPANSIVE REGION.

..GUIDANCE/UNCERTAINTY/CONTINUITY ASSESSMENT...

WPC ALASKAN MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS
ALONG WITH ASSOCIATED HIGH RESOLUTION SENSIBLE WEATHER GRIDS HAVE
BEEN PRIMARILY DERIVED FROM A BLEND OF THE 12 UTC GFS...00 UTC
ECMWF...AND OVERALL COMPATABLE 00 UTC ECMWF/NAEFS ENSEMBLE MEANS.
PLACED INCREASING EMPHASIS ON THESE ENSEMBLE MEANS BY/AFTER DAY 5
THURSDAY CONSISTENT WITH GROWING EMBEDDED SYSTEM FORECAST SPREAD.

SCHICHTEL

$$




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