Prognostic Meteorological Discussion
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FXAK02 KWNH 271749
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 PM EDT SUN JUL 27 2014

VALID 12Z THU JUL 31 2014 - 12Z MON AUG 04 2014

MODELS AND ENSEMBLES CONTINUE TO HIGHLIGHT OMEGA BLOCKING FOR MUCH
OF THE COMING WEEK OVER MID-UPPER LATITUDES COMPRISED OF SLOW
MOVING AND UNSETTLING CLOSED MEAN LOWS CENTERED JUST SOUTH OF THE
WRN ALEUTIANS AND OVER THE GULF OF ALASKA THAT BOOKEND AN
AMPLIFIED RIDGE EXTENDING NORTHWARD THROUGH THE CENTRAL ALEUTIANS
TO ACROSS THE BERING SEA. THIS PATTERN FAVORS WRAPPING PCPN UP
INTO THE WRN ALEUTIANS WITH SOME MODERATE AMOUNTS INTO COASTAL SRN
AND SERN ALASKA AS HARD TO PREDICT IMPULSES ALOFT ROTATE SOME
ACTIVITY EVEN WITH LESS FAVORABLE LOWER LEVEL FLOW. RIDGE
AMPLITUDE MEANWHILE FAVORS COOLING WITH NRN STREAM TROUGHING AND
SOME PCPN DOWN THROUGH THE N-CENTRAL INTERIOR THOUGH
CONTINUITY/DETAILS ARE LESS CLEAR IN GUIDANCE.

THE 06 UTC GFS ENSEMBLE MEAN AND 00 UTC NAEFS/ECMWF ENSEMBLE MEANS
SEEM REASONABLY COMPATABLE AND OFFER GOOD CONTINUITY TO ALLOW WPC
PREFERENCE FOR A COMPOSITE BLEND SOLUTION DAYS 4-8 AS A BASIS FOR
PRODUCTION OF THE WHOLE WPC MEDIUM-RANGE FORECAST PRODUCT SUITE.
ALSO INCLUDED SOME INPUT FROM THE 06 UTC GFS AND 00 UTC ECMWF THU
INTO FRI MORNING...BUT LATER RELIED UPON AN ENSEMBLE APPROACH IN A
PERIOD OF INCREASED DETERMINISTIC MODEL VARIANCE. THE GFS AND
ESPECIALLY THE ECMWF ARE FASTER TO BREAK DOWN THE BLOCK THAN THEIR
CORRESPONDING ENSEMBLES AND THAT SEEMS LESS LIKELY GIVEN THE
NATURE OF BLOCKS. MANUAL MODIFICATIONS AGAIN ACTED TO MAINTAIN
DECENT OCEANIC SURFACE LOW DEPTHS FOR THE COMING WEEK CONSISTENT
WITH LINGERING MID-UPPER SUPPORT.

SCHICHTEL

$$




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