Prognostic Meteorological Discussion
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FXAK02 KWNH 271904
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 PM EDT WED JUL 27 2016

VALID 12Z SUN JUL 31 2016 - 12Z THU AUG 04 2016

SPLIT-FLOW PATTERN FEATURES ANOTHER MODERATE ARCTIC SHORTWAVE
MIGRATION ACROSS THE STATE FROM NORTHWEST TO SOUTHEAST --- IN THE
DAY 4 TIME FRAME. THIS COOLER AIR SEEPS INTO THE GULF OF ALASKA
AND RE-INVIGORATES A MOIST CYCLONIC FLOW FOR THE COAST AND FRONTAL
PRECIPITATION AND BREEZY CONDITIONS ACROSS THE INTERIOR.

THE CHALLENGE YESTERDAY WAS WHAT THE FLOW PATTERN WOULD LOOK LIKE
ALOFT IN THE GULF OF ALASKA AND SOUTHERN BERING SEA ONCE THE
MID-LEVEL AND UPPER-LEVEL EXITS THE STATE. SEEMS THE 27/00Z CYCLE
CLEARED THIS UP --- IN A SENSE --- IT HAS. THE 27/00Z GFS `LET GO`
OF IT`S SLOW SOUTHERN TROUGH SOLUTION AND `PINCHED OFF LOW` IN THE
SOUTHERN BERING--- AND LOOKED MORE LIKE THE ECMWF IN THE GULF OF
ALASKA. ON THE OTHER END OF THE SPECTRUM---THE 27/00Z ECMWF DID
PROG A CLOSED H5 LOW IN ITS 26/00Z. BUT ITS 27/00Z SOLUTION IS A
TAD WEST AND NORTH WITH ITS PREVIOUS POSITION NOW.

ACROSS THE ARCTIC CIRCLE AND NORTHWARD --- A COOLER WESTERLY FLOW
FROM NORTHEAST RUSSIA WILL PREVAIL AFTER DAY 4 AND A POLAR CYCLONE
SHOULD LIFT AWAY FROM THE REGION IN THE 27/00Z GUIDANCE--- BUT THE
ECMWF DOES POSSESS ADDITIONAL SHORTWAVE ARCTIC ENERGY THAT POSES A
SECONDARY CHALLENGE FOR DAY 6 INTO DAY 7. A WARM FRONT AND A
WEST-SOUTHWEST COMPONENT TO THE FLOW.

USING THE 27/00Z ECENS/DETERMINISTIC ECMWF DOES SEEM TO WORK WELL
ALOFT ACROSS THE SOUTHWEST INTERIOR DURING THE DAY4-5 ARCTIC WAVE
MIGRATION --- ENOUGH DETAIL FOR DAY 6 ACROSS THE ARCTIC AND GULF
OF ALASKA... THEN DOWNSTREAM INTO THE CENTRAL PORTION OF NORTH
AMERICA --- TO CARRY IT THROUGH THIS PACKAGE (GRIDS/DAILY
GRAPHICS).

VOJTESAK

$$





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