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Alaska Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1835Z Aug 26, 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
235 PM EDT TUE AUG 26 2014

VALID 12Z SAT AUG 30 2014 - 12Z WED SEP 03 2014

MEDIUM RANGE PERIOD FOR ALASKA CONTINUED WITH THE 'TASTE OF
AUTUMN' THEME TODAY...USING THE 26/00Z ECENS AND THE PRIOR 2
CYCLES OF THE DETERMINISTIC ECMWF--WITH A FEW EXCEPTIONS.

THE EUROPEAN CENTRE VERSION OF THE ARCTIC LOW SOLUTION WAS FAVORED
OVER THE GFS...WITH LESS EASTWARD PROGRESSION ABOVE THE ARCTIC
CIRCLE AND DOWNSTREAM ACROSS THE YUKON AND NORTHWEST TERRITORIES.
ACROSS THE MID-LATITUDE PACIFIC...THE SOLUTION IS FLATTER AND
BETTER FITS THE UPPER-LEVEL FLOW PATTERN...WITH A
PROGRESSIVELY-ACTIVE GULF OF ALASKA...PANHANDLE AND WESTERN NORTH
AMERICAN COASTLINE.

THE DETERMINISTIC 26/00Z ECMWF DID SEEM TO LOSE A LITTLE TOO MUCH
CONTINUITY AROUND DAY 5 INVOF BRISTOL BAY/YUKON DELTA REGION WITH
ITS SURFACE LOW TRACK...AND THE 25/12Z ECMWF WAS A LITTLE CLOSER
TO THE 26/00Z ECENS WITH RESPECT TO TRACK AND DEPTH. BEYOND DAY
6...ITS (THE ECMWF) PROPENSITY FOR OVER-DEVELOPING EVERY MID-LEVEL
INTO A DEEP SURFACE CYCLONE IN NORTHEAST SIBERIA AND THE BERING
STRAIT DID NOT QUITE FIT THE PERSISTENT AND MORE CONSISTENT
250-MILLIBAR TO 500-MILLIBAR PATTERN ESTABLISHING ITSELF ALONG 50N
FROM THE DATELINE (ALEUTIANS) EASTWARD TO 130W LONGITUDE (THE
PACIFIC NORTHWEST COAST OF THE MAINLAND). BLENDED 80% OF THE ECENS
MEAN AFTER DAY 6 TO MITIGATE THE AREAS WHERE--AT TIMES--THE
DETERMINISTIC ECMWF TENDS TO 'OVERPLAY THE PATTERN' DOWNSTREAM. 

THE SELECTED BLEND CONTINUED WITH A DOWNWARD TREND IN
TEMPERATURES...WELL BELOW AVERAGE...850MB TEMP ANOMALIES OF 2
STANDARD DEVIATIONS. THIS COULD BE JUST ENOUGH TO GENERATE A FEW
POCKETS OF SNOWFALL FROM THE PRECIPITATION SHIELD(S) ROTATING
SOUTHWEST TO NORTHEAST DURING THE FIRST HALF OF THE MEDIUM RANGE
PERIOD. DID NOT THINK THE PATTERN ALOFT WAS THAT
'UNPREDICTABLE'...IE 500 HEIGHTS BELOW 522 DM...TO DOWNPLAY THE
INCREASING POTENTIAL ALOFT FOR AN 'AUTUMN' SENSIBLE WEATHER
PATTERN THAT WOULD BE AN ABRUPT CHANGE FROM THE 'SEMI-PERSISTENT'
DAMPNESS AND CLOUDY PATTERN.

VOJTESAK