Prognostic Meteorological Discussion
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FXAK02 KWNH 172001
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EST WED JAN 17 2018

VALID 12Z SUN JAN 21 2018 - 12Z THU JAN 25 2018

ONCE AGAIN...A RIDGE WILL IN GENERAL CENTER ITSELF OVER THE BERING
SEA/CHUKOTSK PENINSULA DURING THE MEDIUM RANGE PERIOD. A TROUGH
WILL SET UP OVER THE GULF OF ALASKA...MEANWHILE FRONTAL SYSTEMS
WILL MOVE TO THE SOUTH OF IT IN THE PACIFIC.  AN OCCLUDED FRONT
WILL APPROACH THE PANHANDLE BY DAY 7/WEDNESDAY...MOVING INLAND
DURING THE DAY AND DYING AS IT CROSSES MOUNTAINS. THE 12Z GFS AND
00Z ECMWF HAD DIFFERENCES WITH THE SURFACE LOW THAT SPLITS OFF
FROM A MATURE OCCLUDED FRONT IN THE BERING SEA ON MONDAY...WITH
THE 12Z GFS BEING FASTER AND NOT AS DEEP WITH THE LOW. THIS WILL
IMPACT THE EVOLUTION OF THE TRACK WITH THE LOW GOING INTO
TUESDAY...HOWEVER BOTH SETS OF GUIDANCE KEEPS IT PRETTY FAR SOUTH
OF THE SOUTHERN ALASKAN COAST...BUT THE TIMING WILL IMPACT THE
PANHANDLE/BRITISH COLUMBIA COAST IN TERMS OF PRECIPITATION GOING
INTO WEDNESDAY AND THURSDAY. THE 06Z GEFS/00Z ECENS WERE IN BETTER
AGREEMENT WITH THE TRACK OF THIS LOW. WPC BLENDED THE 12Z GFS/00Z
ECMWF AND THE 06Z GEFS/00Z ECENS AND PUT MORE WEIGHT ON THE
ENSEMBLE MEANS BY THE END OF THE MEDIUM RANGE PERIOD.

BY MONDAY...THE CHANCE OF PRECIPITATION WILL STEADILY INCREASE
ALONG THE SOUTHERN ALASKAN COAST AND CONTINUE THROUGH THURSDAY.
THE AMOUNT OF PRECIPITATION AND TIMING WILL BE DEPENDENT ON THE
POSITION OF THE UPPER LOW/HOW THE SURFACE LOW EVOLVES AS IT MOVES
ACROSS THE PACIFIC AND TOWARD SOUTHERN ALASKAN
COAST/PANHANDLE/WESTERN BRITISH COLUMBIA. TEMPERATURES WILL BE
BELOW NORMAL ACROSS THE INTERIOR OF ALASKA AND INTO WESTERN
ALASKA/THE ALASKAN PENINSULA FOR MOST OF THE WEEK.  TEMPERATURES
WILL BE NEAR NORMAL FROM SOUTHEASTERN ALASKA TO THE PANHANDLE
REGION THROUGH THE MEDIUM RANGE PERIOD.

REINHART

$$





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