Prognostic Meteorological Discussion
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FXAK02 KWNH 161926
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EST TUE JAN 16 2018

VALID 12Z SAT JAN 20 2018 - 12Z WED JAN 24 2018

FOR THE MEDIUM RANGE FORECAST PERIOD...A RIDGE WILL CENTER ITSELF
OVER NORTHERN ALASKA EXTENDING FROM ASIA...WITH SYSTEMS
UNDERCUTTING THE RIDGE INTO THE GULF OF ALASKA THROUGH THE
FORECAST PERIOD. A LARGE OCCLUSION WILL APPROACH WESTERN
ALASKA/ALEUTIAN ISLANDS BY SATURDAY AND INTO SUNDAY...AND MOVE
INTO THE GULF OF ALASKA BY DAY 6/MONDAY. AT FIRST...THE 06Z GFS
AND 00Z ECMWF DIFFERED ON THE SOLUTION OF THIS PARTICULAR SURFACE
LOW...WITH THE 06Z GFS SHOWING THE SURFACE LOW ABSORBING INTO THE
TROUGH SET UP ALONG THE SOUTHERN ALASKAN COAST. THE 00Z ECMWF
SHOWED THE LOW MOVING FARTHER SOUTH INTO THE NORTH PACIFIC. THE
12Z GFS SHOWED A SIMILAR PATH TO THIS LOW. THIS SYSTEM WILL
APPROACH THE COAST BY DAY 8/WEDNESDAY. GIVEN THAT THE RIDGE OVER
ALASKA WILL STAY IN PLACE OVER THE MEDIUM RANGE PERIOD, THE
SOUTHERN TRACK SEEMS MORE LIKELY OF A SOLUTION. OTHERWISE...MOST
OF THE GUIDANCE SEEMED IN FAIR AGREEMENT THUS TOOK A BLEND OF THE
00Z ECMWF/12Z GFS AND THE 06Z GEFS MEAN/00Z ECENS WITH MORE WEIGHT
ON THE ENSEMBLE MEANS BY THE END OF THE PERIOD.

PRECIPITATION WILL BEGIN TO STEADILY INCREASE BY MONDAY AS AN
INCREASE IN MOISTURE FROM THE GULF OF ALASKA MOVES NORTHWARD INTO
THE SOUTHERN ALASKAN COAST.  THIS INCREASE IN CHANCE OF
PRECIPITATION WILL PERSIST THROUGH WEDNESDAY AND IS EXPECTED TO BE
CONFINED TO THE COAST.  TEMPERATURES ARE EXPECTED TO BE NEAR
AVERAGE.

REINHART

$$





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