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Prognostic Meteorological Discussion (PMD)

Issued by National Weather Service (NWS)

                            
000
FXAK02 KWNH 211910
PMDAK 

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
309 PM EDT Tue May 21 2019

Valid 12Z Sat May 25 2019 - 12Z Wed May 29 2019

Models continue to show relatively good agreement for this weekend
(days 4-5) with the consensus of a low pressure system crossing
the eastern Aleutians and driving an occluded front across the
Peninsula and towards the Southern Coast. This would result in a
period of potentially heavy precipitation, focusing along the
coast of the Peninsula, Kodiak Island, and the Southern Mainland
Coast. Given the consensus, the forecast for days 4-5 was based on
a majority deterministic blend between the 00z ECMWF/12z GFS.

Beyond this weekend, the ensembles show very good agreement
through day 8 (next Wednesday) as the initial low lingers in the
Bering Sea as another upper shortwave slides in underneath, and
gradually weakens strong upper ridging across the eastern
Pacific/western North America into northern Alaska. This results
in another area of low pressure moving across or just south of the
Aleutians early next week with generally showery activity along
the coast. Deterministic model solutions show increasing
variability and noise with respect to timing and intensity details
of individual systems sliding through the larger scale trough. Due
to this, the blend used increasing weighting of the ECENS/GEFS
ensemble means beyond day 5. The overall forecast blend for the
entire period (Sat - Wed) resulted in a forecast close to
yesterdays continuity.

Santorelli

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 precipitation across portions of the Alaska Panhandle and
mainland Alaska, Fri-Mon, May 24-May 27.

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

$$