Prognostic Meteorological Discussion
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FXAK02 KWNH 221917
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
317 PM EDT FRI JUL 22 2016

VALID 12Z TUE JUL 26 2016 - 12Z SAT JUL 30 2016

...PATTERN OVERVIEW/GUIDANCE AND UNCERTAINTY AND WEATHER/THREAT
HIGHLIGHTS...

THE LATEST GUIDANCE ISSUED RECENTLY SEEMS TO BE INDICATING THAT
THE DEVELOPING TROUGH IN THE MEDIUM RANGE OVER WESTERN ALASKA AND
THE ADJACENT GULF MAY BE MORE PROGRESSIVE LATER IN THE
FORECAST...AS THERE IS MORE EVIDENCE THAT THE ACTIVITY OVER
NORTHEAST SIBERIA/THE NORTHERN BERING SEA AND THE ADJACENT ARCTIC
APPEARS MUCH MORE ACTIVE THAN EARLIER SEEN.  UNFORTUNATELY...THERE
IS STILL SO MUCH SPREAD LATER IN THE FORECAST THAT ANY SIGNIFICANT
SYNOPTIC FEATURES APPEAR TO BE SMOOTHED OUT IN THE MEANS.

THAT SAID...AN ACTIVE PATTERN ALONG THE NORTHERN AND NORTHWEST
AREAS OF THE FORECAST DOMAIN COULD LEAD TO A VERY ACTIVE WET
PATTERN ACROSS THE CENTRAL AND NORTHERN PARTS OF THE STATE AS WE
HEAD INTO THE END OF JULY.

TO START OFF...A DEEPENING TROUGH OVER SOUTHWEST ALASKA ON
TUESDAY/DAY 4 IS SUPPORTED BY THE OPERATIONAL 12Z GFS/ECMWF WITH
CYCLONIC FLOW ACROSS THE ENTIRE NORTHERN GULF AND NORTHEAST
PACIFIC. A DEEP UPPER LOW LOCATED ABOUT 500 TO 6O0 MILES NORTH OF
THE NORTHERN SIBERIAN COAST IS EXPECTED TO REMAIN A POWERFUL
PLAYER IN THE FORECAST AS IT MOVES AND REFORMS UNDER THE INFLUENCE
OF SHORTWAVE FEATURES THAT ARE HARD TO RESOLVE BUT COULD HELP TO
KEEP THE FLOW FARTHER SOUTH MORE PROGRESSIVE AS ANY ARCTIC SYSTEMS
BEING TO MOVE SOUTHEAST ACROSS THE NORTHERN BERING SEA INTO
WESTERN ALASKA BY DAYS 5 AND 6/WEDNESDAY AND THURSDAY.  BOTH THE
LATEST OPERATIONAL GFS/ECMWF KEEP A DEEP LOW JUST NORTH OF ALASKA
BY LATE IN THE FORECAST ALTHOUGH THERE IS INCREASING SPREAD ON
SHORTWAVE FEATURES EMANATING FROM THIS SYSTEM OR HOW THESE SYSTEMS
INTERACT WITH THE TROUGHING OVER SOUTHWEST ALASKA...THAT THEN
HEADS EASTWARD ACROSS THE NORTHEAST PACIFIC ON DAYS 7 AND 8/FRIDAY
AND SATURDAY.  IT IS DURING THIS PERIOD THAT ANY DETAILS ARE LOST
WITHIN THE ENSEMBLE MEAN SPREAD.

WET WEATHER WILL OCCUR ALONG THE GULF COAST WITH THE TROUGHING
BEGIN FOCUSED OVER THAT REGION EARLY IN THE FORECAST BUT APPEARS
TO HEAD EASTWARD BY THE WEEKEND.  WET WEATHER WILL MOVE OUT OF
NORTHEAST ALASKA WITH A SHORTWAVE SYSTEM ON TUESDAY/DAY 4 BUT WILL
THEN REDEVELOP BY WEDNESDAY AND THURSDAY ACROSS THE NORTH AS
SEVERAL POTENTIAL SYSTEMS MOVE ACROSS THE REGION.

KOCIN

$$




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