Prognostic Meteorological Discussion
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FXAK02 KWNH 161939
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
338 PM EDT WED AUG 16 2017

VALID 12Z SUN AUG 20 2017 - 12Z THU AUG 24 2017

THE UPPER-LEVEL PATTERN STARTS OFF AND REMAINS BELOW AVG
THROUGHOUT THE FORECAST PERIOD, PER 500MB HEIGHTS. BOTH THE GEFS
AND ECMWF MEANS INDICATE THIS REGIME AT 500MB, GENERALLY 1 TO 1.5
STANDARD DEVIATIONS BELOW AVG. THE FORECAST PERIOD STARTS OFF WITH
A COLD CLOSED MID TO UPPER LOW OVER THE WESTERN/SWRN PORTION OF
THE STATE WITH A WAVE OF PAC UPPER DYNAMICS UNDERCUTTING THE
LARGER FEATURE. BROAD SWRLY UPPER-LEVEL FLOW SHOULD BE IDEAL FOR
THE START OF A RATHER WET REGIME INTO THE PANHANDLE AND SOUTHERN
COAST. BY MON, THE SPLIT FLOW WILL THEN EITHER PHASE OVER THE GULF
OF AK OR THE LEADING SOUTHERN/PAC STREAM SHORT WAVE ARRIVES INTO
THE PANHANDLE, WHILE THE CLOSED LOW STILL DEEPENS OVER THE GULF OF
AK. EITHER WAY, EACH SCENARIO PRODUCES A RELATIVELY DEEP AREA OF
SURFACE LOW PRESSURE. THE VORTICITY ALONG THE PAC JET APPEARS TO
CONTAIN THE REMNANTS OF TYPHOON BANYAN, EXPECT ANOMALOUS MOISTURE
FLUX INTO THE PANHANDLE FROM LATE WEEKEND THROUGH MID NEXT WEEK.
AS THIS LARGE SYSTEM GRADUALLY DEPARTS OFF TO THE SOUTH AND EAST,
ANOTHER RATHER STRONG UPPER TROUGH WILL APPROACH FROM UPSTREAM. SO
NEXT THURS UPPER PATTERN WILL MIMIC SUNDAYS QUITE CLOSELY. WPC
REALLY FELT COMFORTABLE WITH A 60 PERCENT OF THE FORECAST BLEND
BEING OPERATIONAL GUIDANCE THROUGH MON AND SHIFTED TO 50 TO 70
PERCENT OF THE BLEND BEING MEANS NEXT TUES-THURS. AS MENTIONED,
THIS SHOULD SPELL A VERY WET NUMBER OF DAYS FOR THE SOUTHERN
PORTION OF THE STATE INTO THE PANHANDLE.

MUSHER


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