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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1859Z Aug 30, 2014)
 
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Abbreviations and acronyms used in this product
 
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT SAT AUG 30 2014

VALID 12Z WED SEP 03 2014 - 12Z SUN SEP 07 2014

THE MEDIUM RANGE ALASKAN WEATHER PATTERN REMAINS HIGHLIGHTED BY A
MAJOR ARCTIC VORTEX NEAR THE NORTH SLOPE FOR MUCH OF NEXT WEEK
ALLOWING FOR A PERIOD OF MID-UPPER LEVEL TROUGHING FROM THE ARCTIC
OCEAN THROUGH THE INTERIOR THAT LINGERS INTO NEXT WEEKEND. STILL
EXPECT BELOW NORMAL TEMPS FOR MUCH OF ALASKA AS 500/700 MB HEIGHT
ANOMALIES WILL CENTER 2-3 STANDARD DEVIATIONS BELOW NORMAL NORTH
OF THE ARCTIC CIRCLE. THE PATTERN SHOULD ALLOW MODEST LINGERING
IMPULSES AND SURFACE DEVELOPMENT UNDERNEATH OVER THE ALASKAN
SRN/SERN TIER AND THE NRN GULF OF AK CHANNELING OVERTOP A
PERSISENT NE PAC MID-UPPER LEVEL RIDGE. 

MEANWHILE...THE UPSTREAM DEVELOPMENT ACROSS THE MID-UPPER PACIFIC
LATITUDES OF A MEAN MID-UPPER LEVEL TROUGH JUST SOUTH OF THE
ALEUTIANS SHOULD FAVOR ASSOCIATED CYCLOGENESIS/FRONTOGENESIS THAT
SEEMS MOST LIKELY TO ORGANIZE AND WORK TOWARD THE ALEUTIANS AND SW
ALASKA INTO LATE WEEK AROUND THE WRN PERIPHERY OF THE
AFOREMENTIONED NERN PACIFIC RIDGE. THE 00 AND LATEST 12 UTC ECMWF
IN PARTICUALAR CONTINUE TO SHOW MORE STREAM INTERACTION/PHASING
COMPARED TO OTHER DETERMINISTIC MODELS UP INTO THE BERING SEA/SW
ALASKA NEXT WEEK...BUT THIS DOES NOT SEEM SUPPORTED AT THIS POINT
BY ENOUGH ENSEMBLES TO EMBRACE WITH TOO MUCH VIGOR.

AS UNCERTAINTY IS ABOVE AVERAGE OVER THE FORECAST PERIOD...THE WPC
ALASKAN MEDIUM RANGE PRODUCT SUITE REMAINS DERIVED FROM AN
ENSEMBLE MEAN FORECAST APPROACH. THE 00 UTC GFS ENSEMBLE MEAN WAS
AGAIN PRIMARILY USED AS IT BEST MAINTAINS WPC PATTERN CONTINUITY
WITH EMBEDDED FEATURES WHILE STAYING REASONABLY COMPATABLE ALOFT
WITH 00 UTC ECMWF/NAEFS ENSEMBLE MEANS.

SCHICHTEL