Prognostic Meteorological Discussion
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
129 PM EST FRI JAN 19 2018

VALID 12Z TUE JAN 23 2018 - 12Z SAT JAN 27 2018

RECENT MODELS AND ENSEMBLES REASONABLY AGREE TO DEVELOP AND
MAINTAIN AN AMPLIFIED AND BLOCKY LARGER SCALE MEDIUM RANGE FLOW
PATTERN OVER THE ALASKAN REGION AND VICINITY NEXT WEEK. THIS
PATTERN WILL BE HIGHLIGHTED ALOFT BY A NEAR DATELINE CENTERED HIGH
LATITUDE RIDGE SANDWICHED BY UNSETTLED TROUGHS OFF NERN ASIA AND
ANOTHER COLD TROUGH FROM THE ARCTIC AND NORTH SLOPE DOWN ACROSS
THE INTERIOR THROUGH A GULF OF ALASKA MEAN CLOSED LOW. GULF OF
ALASKA MARITIME INTERESTS AND COOLED SRN/SERN ALASKA COASTAL
COMMUNITIES/TERRAIN WILL BE THREATENED BY PERIODS OF ENHANCED
WINDS/MOISTURE AND WINTER PRECIPITATION WRAPPING AROUND A SERIES
OF ORGANIZED OFFSHORE LOWS ALL NEXT WEEK.

PREFER AN ENSEMBLE MEAN FORECAST APPROACH DAYS 4-8 AS LATEST
DETERMINISTIC MODEL GUIDANCE OFFERS LESS MANAGEABLE FORECAST
VARIABILILTY WITH EMBEDDED WEATHER FEATURES DESPITE A REASONABLY
SIMILAR LARGER SCALE FLOW EVOLUTION ALOFT. THE WPC PRODUCT SUITE
WAS PRIMARILTY DERIVED FROM THE 06 UTC GEFS MEAN THAT HAS SLIGHTLY
BETTER CONTINUITY THAN THE 00 UTC GEFS/NAEFS MEANS. OPTED TO
DISCOUNT THE 00 UTC ECMWF ENSEMBLE MEAN AS A LESS LIKELY OUTLIER
BRINGING MUCH MORE HEIGHT RISES NORTHWARD NEXT WEEK OVER THE GULF
OF ALASKA. PREFER INSTEAD NRN STREAM TROUGHING TO BE MORE DOMINANT
DUG DOWN OVER THE GULF OF ALASKA NEXT WEEK CONSIDERING EXPECTED
AMPLIFICATION AND OVERALL BLOCKY LOOK SLATED TO DEVELOP OVER THE
HIGH LATUTUDES IN MOST DETERMINISTIC MODEL AND ENSEMBLE
SYSTEMS...INCLUDING THE 00 UTC AND NEWEST 12 UTC ECMWF RUNS. THIS
WPC/ALASKAN WFO COLLABORATED SOLUTION MAINTAINS EXCELLENT WPC
FORECAST CONTINUITY IN A PATTERN WITH NEAR TO SLIGHTLY ABOVE
NORMAL PREDICTABILITY.

SCHICHTEL

$$





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