Prognostic Meteorological Discussion
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FXAK02 KWNH 101843
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ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
142 PM EST SAT DEC 10 2016

VALID 12Z WED DEC 14 2016 - 12Z SUN DEC 18 2016

ENSEMBLES REMAIN IN SOMEWHAT DECENT AGREEMENT THROUGH THE PERIOD,
BUT WITH MORE NOTICEABLE DIFFERENCES BY THE END OF NEXT WEEK. THE
ECMWF ENSEMBLES REMAIN UNCHARACTERISTICALLY QUICKER AND LESS
AMPLIFIED OVER THE EASTERN PACIFIC FROM THE SUBTROPICS NORTHWARD
INTO THE HIGH LATITUDES WHILE THE GEFS ENSEMBLES WERE GENERALLY
SLOWER AND DEEPER. GIVEN THE UPSTREAM AND DOWNSTREAM AMPLITUDE OF
THE UPPER FLOW (DEEP LOW OVER KAMCHATKA AND SIGNIFICANT TROUGHING
OVER THE NW CONUS AND SW CANADA) OPTED TO PUT MUCH MORE WEIGHT IN
THE 06Z GEFS MEAN OVER THE 00Z ECMWF ENSEMBLE MEAN. OF THE
DETERMINISTIC SOLUTIONS, THE 06Z GFS WAS CLOSEST TO THE ENSEMBLE
CONSENSUS (AND THEN THE 06Z GEFS MEAN) FOR MOST OF THE PERIOD
WHILE THE 00Z ECMWF AND 12Z GFS WERE JUST DIFFERENT ENOUGH THAT
ONLY A MINORITY WEIGHTING WAS USED (ECMWF ONLY). INITIAL QUESTION
IS THE TRACK OF A WESTERN BERING SEA SYSTEM NEXT THURSDAY (12Z GFS
WAS SUDDENLY FATHER SOUTHEAST, SOMEWHAT LIKE THE 00Z ECMWF AND NOW
LIKE THE 12Z ECMWF), BUT OPTED TO STAY NEAR THE ENSEMBLE CONSENSUS
UNTIL MORE CONSISTENCY IS SEEN -- THOUGH THE TREND HAS BEEN A BIT
FARTHER SOUTHEAST.

LINGERING QUESTION THEN BECOMES HOW MUCH THE RIDGE HOLDS ON
THROUGH THE INTERIOR AND WHAT SHORTWAVES MAY TRY TO CHIP AWAY AT
THE TOP AND BOTTOM OF THE RIDGE. FOR NOW, HELD ONTO THE RIDGE
THOUGH THE FLOW WILL BE A BIT CHAOTIC UPSTREAM, MEANING THE
POTENTIAL IS THERE FOR A DEEP SYSTEM TO PUSH THE RIDGE DOWN/EAST.
12Z GFS IS RATHER EXTREME EXAMPLE OF THIS WITH A 923MB LOW IN THE
BERING SEA NEXT WEEKEND INTO NEXT MONDAY.

TEMPERATURES WILL SLOWLY RISE FROM WEST TO EAST THROUGH THE PERIOD
AS THE COLD AIR RELUCTANTLY ABATES. WESTERN COASTAL AREAS SHOULD
SEE A WARM SURGE AND NEAR RECORD WARM TEMPERATURES WHERE THE WARM
FRONT CAN DISLODGE THE COLD AIR. PRECIPITATION WILL FOCUS IN THE
ALEUTIANS AND WESTERN AREAS BUT SLOWLY PUSH EASTWARD DEPENDING ON
HOW THE UPPER/SFC PATTERN EVOLVES AND HOW MUCH RIDGING HOLDS
TIGHT.


FRACASSO



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