Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
736 PM EDT Mon Apr 15 2024

Valid 12Z Fri Apr 19 2024 - 12Z Tue Apr 23 2024

...Synoptic Overview...

An amplified upper level flow pattern is forecast to be in place
across the Alaska domain for the end of the week, with a strong
ridge axis and closed upper high situated over the Yukon
Territory, and a broad upper low several hundred miles south of
the Alaska Peninsula and weaker low over the northern Bering Sea. 
Onshore flow directed towards the coast will produce periods of
moderate precipitation from the Alaska Peninsula to the Prince
William Sound, and abating in intensity going into the weekend.  A
second area of low pressure will likely develop over the Aleutians
by early next week with the Gulf low weakening over time, and a
frontal boundary will be draped across the northern half of Alaska.


...Guidance Evaluation and Preferences...

The 12Z model guidance suite, along with the 18Z GFS/GEFS mean,
are in reasonably good synoptic scale agreement on Friday.  The
CMC takes the main Gulf low farther to the north by Saturday
towards the coast, and this continues going into Sunday with its
solution over the southern Bering with the surface low, while the
consensus favors a position a few hundred miles south of Kodiak
Island.  Going into Monday, the GFS remains stronger with the Gulf
low while the CMC/ECMWF weaken it substantially more.  Model
spread becomes noteworthy for the next low pressure system
approaching the Aleutians/Bering Sea region for early next week,
with the CMC well to the south of the GFS/ECMWF, and then the GFS
is farther west with the main low going into next Tuesday.  The
WPC fronts/pressures forecast was primarily derived from a
multi-deterministic model blend on Friday, and then gradually
increasing percentages of the ensemble means through next Tuesday
as storm system differences become larger.  Lesser weighting was
applied to the CMC solution given the differences noted.


...Weather/Hazards Highlights...

Coastal rain and mountain snow is expected to be moderate to
locally heavy going into the second half of the work week from the
southern Alaska Peninsula to the Prince William Sound region with
continuing onshore flow northeast of the Gulf low, with the
heaviest precipitation likely on Thursday.  There should be
gradual abatement in the precipitation going into the weekend as
the moisture flux towards the coast weakens.  Lighter showers are
possible farther inland across western portions of mainland
Alaska.  Temperatures are generally expected to be pleasantly mild
with readings in the upper 40s to upper 50s for highs across most
Interior locations south of the Brooks Range, and generally 40-45
degrees near the southern coastal areas.  A cooling trend is
likely by early next week as the upper ridge axis breaks down. 
The Brooks Range will be the demarcation for much colder
conditions across the North Slope and extending to the Arctic
Coast. 

Hamrick


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

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