THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


ALASKA EXTENDED FORECAST DISCUSSION




ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT MON SEP 01 2014

VALID 12Z FRI SEP 05 2014 - 12Z TUE SEP 09 2014

THE ALASKAN FLOW PATTERN OVER THE NEXT FEW DAYS IS HIGHLIGHTED BY
A COLD AND UNSETTLING ARCTIC VORTEX CENTERED OFF THE NORTH SLOPE
WITH AN ASSOCIATED INFLUENCE THROUGH THE INTERIOR. THIS VORTEX
MOVES STEADILY EASTWARD LATE WEEK LEADING TO MODERATING ALASKAN
WEATHER. THIS OCCURS AS AMPLE UPSTREAM TROUGH ENERGY PROGRESSES
SEWD FROM THE BERING SEA TO SW/SRN AK AND THE GULF OF AK/SE AK.
THIS AND LEADING MID-LATITUDE TROUGH ENERGY NOW SEEMS TO SUPPORT
BETTER ORGANIZED SURFACE SYSTEM DEVELOPMENT AND PCPN/WEATHER FOCUS
OVERTOP A NE PACIFIC MID-UPPER LEVEL RIDGE FRIDAY-SUNDAY.

MEANWHILE...UPSTREAM DEVELOPMENT ACROSS THE MID-UPPER PACIFIC
LATITUDES OF A AMPLIFIED MEAN MID-UPPER LEVEL TROUGH JUST SOUTH OF
THE ALEUTIANS SHOULD FAVOR POTENT CYCLOGENESIS/FRONTOGENESIS THAT
WELL CLUSTERED MODEL AND ENSEMBLE GUIDANCE ORGANIZES AND WORKS
WINDS/PCPN TOWARD THE ALEUTIANS AND SW ALASKA NEXT WEEKEND AND
EARLY NEXT WEEK ON DAYS 5-8 AROUND THE WRN PERIPHERY OF THE
AFOREMENTIONED NERN PACIFIC RIDGE.

BACK UP NORTH...GUIDANCE IS MORE MIXED SO FORECAST UNCERTAINTY IS
NOT STELLAR...BUT THERE SEEMS DECENT POTENTIAL FOR ANOTHER
ORGANIZED ARCTIC SYSTEM TO PASS NORTH OF THE NORTH SLOPE BY EARLY
NEXT WEEK THAT COULD FORCE A TRAILING FRONT TO NWRN AK.

MODELS AND ENSEMBLES OVERALL NOW OFFER EVEN MORE COMPATABLE
GUIDANCE THAN HAS BEEN TO CASE IN RECENT DAYS.
HOWEVER...DIFFERENCES BETWEEN ENSEMBLE MEANS AND THEIR RESPECTIVE
DETERMINISTIC MODEL RUNS STILL LENDS PAUSE AT LONG TIME FRAMES.
ACCORDINGLY...THE WPC ALASKAN MEDIUM RANGE PRODUCT SUITE HAS BEEN
PRIMARILY DERIVED FROM A BLEND OF COMPATABLE GUIDANCE FROM THE 06
UTC GFS/GEFS MEAN AND 00 UTC ECMWF/ECMWF ENSEMBLE MEAN DAYS 4/5
AND THEN JUST THE 06 UTC GEFS MEAN AND 00 UTC ECMWF ENSEMBLE MEAN
DAYS 6-8.

SCHICHTEL





Last Updated: 236 PM EDT MON SEP 01 2014