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FXAK02 KWNH 302322
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
721 PM EDT Thu May 30 2024

Valid 12Z Mon Jun 03 2024 - 12Z Fri Jun 07 2024

...Overview...

A closed upper low south of the Alaska Peninsula to start the
period on Monday will move into the Gulf Tuesday-Wednesday. This
should support a modestly deep surface system in the Gulf of
Alaska and a period of heavy precipitation across Southeast Alaska
and the interior mountains. Meanwhile, an upper low in the Arctic
looks to send at least some energy southward into the Bering Sea
where there is some support for a modestly deep upper low by late
period, while several weaker shortwaves traverse the southern side
of this mean troughing south of the Aleutians and towards the
Gulf. Over the Mainland itself, upper ridging should build.


...Guidance Evaluation and Preferences...

The latest guidance shows pretty good agreement in both placement
and strength of the upper low and resulting surface system over
the Gulf Monday to Wednesday, as well as southward progressing
energy from the Arctic through the Bering Strait. By mid-week
though, uncertainty increases substantially with regards to how
much energy dives southward from the Arctic low and how
strong/dominant it becomes over the Bering Sea. The latest 12z
runs of the ECMWF and the GFS both suggest a stronger upper low
reflection over the Bering Sea by next Thursday, with the Gulf
energy/low eventually becoming wrapped up into it. The CMC however
keeps the stronger upper low north over the Arctic with a stronger
system well south of the Aleutians and upper ridge over the Bering
creating a more blocky pattern. The GFS and ECMWF are by far the
strongest with an upper low over the Bering but the AI/ML models
and ensemble means do generally suggest more late period troughing
over the Bering than the CMC does.

The WPC forecast was able to use a blend of the deterministic
models for the first half of the period amidst good model
agreement. Began increasing weighting of the ensemble means late
in the period to help smooth out the harder to resolve details.
For this most part, this maintained good continuity with the
yesterdays WPC forecast as well, through day 7.


...Weather/Hazards Highlights...

The deep upper low and surface system over the Gulf early next
week should bring a period of moderate to heavy precipitation to
much of the Southeast/Panhandle and into parts of the interior
mountains. Several inches of rainfall is possible, especially
along the coast, during this multi-day period. Showers are also
possible farther inland and north/west associated with upper level
energy dropping down the West Coast. Expect temperatures to be
below to well below normal across much of the Southern half of the
Mainland most of the period, as well as the North Slope region
(trending warmer by late week). The beginning of the week should
be warmer than average across the eastern Interior region but may
trend cooler/back towards normal later in the week.

Santorelli


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

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