Prognostic Meteorological Discussion
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FXAK02 KWNH 261921
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
321 PM EDT FRI AUG 26 2016

VALID 12Z TUE AUG 30 2016 - 12Z SAT SEP 03 2016

...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER
HIGHLIGHTS/THREATS...

A COMPLEX FLOW PATTERN UNFOLDS BY TUE WITH WEATHER FOCUSING CLOSED
LOWS/TROUGHS ALOFT OVER KAMCHATKA...JUST SOUTH OF THE
ALEUTIANS...AND OFF SERN AK. THESE ALL SURROUND A BERING/BERING
STRAIT RIDGE. FORECAST SPREAD IS REDUCED COMPARED TO THE LAST FEW
DAYS WITH RECENT GFS/ECMWF RUNS AND ENSEMBLE MEANS.
HOWEVER...LINGERING UNCERTAINTY AND WFO COORDINATION SUPPORTS
PREFERENCE FOR A MIDDLE OF THE ROAD/CONTINUITY SOLUTION MOST IN
LINE WITH THE 00 UTC ECMWF INTO MIDWEEK. THEREAFTER...THE
EXTRATROPICAL TRANSITION OF TYPHOON LIONROCK (FORECAST TO WRAP
NORTHWESTWARD INTO JAPAN THANKS TO AN INCOMING/DIGGING UPPER LOW
IN THE SEA OF JAPAN) WILL HELP BUILD A DOWNSTREAM RIDGE AND THEN
SUPPORT FURTHER CONSOLIDATION/DEEPENING OF A DOWNSTREAM CLOSED
TROUGH/LOW NEAR THE WESTERN ALEUTIANS. A QUESTION REMAINS ON HOW
THIS UNFOLDS AND INTERACTS WITH THE EARLIER WEEK IN SITU UPPER LOW
SOUTH OF THE ALEUTIANS...BUT FORECAST SPREAD HAS DECREASED WITH
RECENT RUNS TO BOLSTER CONFIDENCE. EVEN SO...PREFER A MORE
ENSEMBLE MEAN BASED SOLUTION WITH EMPHASIS ON THE 00 UTC ECMWF
ENSEMBLE MEAN TO MAINTAIN MAX CONTINUITY. THIS SIGNIFICANT WEATHER
FEATURE WOULD SUBSEQUENTLY WORK INTO/ACROSS THE SOUTHERN BERING
SEA LATE IN ABOUT A WEEK IN AMPLIFIED FLOW.

SCHICHTEL

$$





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