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000
FXAK02 KWNH 191912
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
311 PM EDT Mon Aug 19 2019

Valid 12Z Fri Aug 23 2019 - 12Z Tue Aug 27 2019

...Continued rain for the Panhandle...

Upper pattern favors troughing over eastern portions of the
mainland (around 140-150W) with zonal flow across the northeastern
Pacific (50N) which will sustain the moisture plume into the
Panhandle. There remain large timing/track differences with
respect to a second system in this forecast period (Fri-Tue) on
the heels of the lead/deeper system Friday. The former has a good
consensus position/strength and a deterministic blend sufficed to
start. The latter is expected to pass south of the area early next
week (Sun/Mon) but was much quicker per the 00Z ECMWF while the
12Z GFS stalled it south of the Aleutians. 00Z Canadian
represented a good middle ground in track/strength/timing which
weakens it by Sunday south of the area, but mid-level flow would
continue the rain chances for the Panhandle.

For Sun-Tue, Canadian was likely too aggressive to drop a
shortwave around the mean upper low in the Arctic through the
Interior, so a trend toward majority ensemble weighting was used.
Farther south, the ECMWF fell back into line with the consensus as
a weak low likely lifts northeastward toward the Gulf in between
high pressure centers to the WNW/ESE. Cyclonic flow will still
dominate much of the mainland but remain westerly across the
Panhandle with higher rain chances. Multi-day amounts may exceed
several inches, on top of short range amounts from a prior system.

Fracasso


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

- Heavy rain across portions of the Alaska Panhandle, Thu-Sat, Aug
22-Aug 24.

WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:

https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html

$$




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