457
FXAK68 PAFC 150121
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
421 PM AKST Tue Jan 14 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: This
afternoon through Friday afternoon)...

Two storms impact Southcentral Alaska from tonight through
Wednesday, and again from Thursday evening through Friday, with
spells of quieter weather in between. Our current spell of quieter
weather is coming to an end as an occluding low approaches from
the Southwest. Kodiak and parts of Kachemak Bay are already
beginning to see rain and snow from this storm, with precipitation
expected to move into Kenai Peninsula and the north Gulf coast
from the rest of tonight through tomorrow.

Confidence is moderate with precipitation and snow amounts.
Models continue to show some differences with where the plume of
moisture will be directed, leading to uncertainty. However, there
are some aspects of the forecast we have higher confidence in.
First, we continue to expect the highest precipitation/snow
amounts along Eastern Kenai Peninsula, with about 4-8 inches of
snow in the Moose Pass to Seward corridor and in the Whittier and
Portage Valley area. Secondly, models are trending towards a more
southerly track with the upper trough, leading to a lower
likelihood of snow for interior locations from about Anchorage and
north. Finally, confidence is high that with colder temperatures
in place, most locations outside of Kodiak Island will see
precipitation fall as snow.

By Wednesday afternoon, much of the precipitation will come to an
end. Then, attention shifts towards gusty offshore winds as a low
near Yakutat tightens surface pressure gradients. Without good
cold air advection, winds may be gusty but shouldn`t be too much
higher than about 25-35 mph, even at favored gap wind locations
like Seward and Whittier. Drier conditions and clearer skies
persist through Thursday afternoon as a ridge moves through. Then,
by Thursday afternoon, the front of a Bering Sea storm will move
into Southcentral, advecting warmer air and moisture in southerly
flow. For now, most of the precipitation looks to be focused along
the coast, where temperatures climbing into the mid to high 30s
will likely bring rain to some locations. For interior locations,
strong winds aloft may lead to downsloping, reducing precipitation
chances for at least the early part of Friday.

-Chen

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Tuesday through Thursday)...

A fast moving, weak low continues to bring light rain and snow to
the Alaska Peninsula and light snow across the Bristol Bay region.
Additional snow accumulations are expected to be no more than a
trace to a couple inches for areas of Bristol Bay from Dillingham
eastward toward Koliganek. Gusty northwest winds from 30 to 40 mph
on the backside of the low are expected to continue through this
evening for the AKPen before the low moves into the western Gulf.
A ridge of high pressure across the Aleutians today will continue
to shift eastward over southwest Alaska for Thursday, bringing
slightly higher temperature and clear skies ahead of the next
system.

Further west, a strong Pacific low approaches the western
Aleutians tonight, bringing gale and storm force winds for the
western and central Aleutians through Wednesday as the front
moves northeastward. Wind gusts through the central Aleutian gaps
are forecasted to range from 50 to 60 knots and persist into
Thursday morning. As the front lifts northwards into the Bering
Sea by Thursday afternoon, a large swath of gale force winds are
expected from the Pribilof Islands to Nunivak Island as well as
much of the Southwestern Alaskan coast. The lifting front will
also bring strong southeasterly gradient-driven winds through
Kamishak Gap, bringing gale to storm force wind gusts to areas
such as Iliamna and Koliganek. Precipitation beginning tomorrow
morning as snow and a rain/snow mix will switch quickly to all
rain by the afternoon hours for the Western Aleutians.
Precipitation tomorrow afternoon and evening in the Central
Aleutians as snow will change to rain by the late evening hours. A
brief period of accumulating snow is likely in the Pribilof
Islands early Thursday morning before switching to a rain/snow mix
and then rain Thursday afternoon. As precipitation reaches
southwest Alaska by Thursday evening, strong southeasterly flow
should keep typically downsloped regions relatively dry with the
heaviest precipitation falling in higher elevations and in the
Kuskokwim Delta, mainly west of Bethel. Temperatures are expected
to remain cold enough for these regions to see accumulating snow
through Friday morning before switching to a possible rain/snow
mix as precipitation tapers off.


&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

Starting Thursday, a high amplitude weather pattern will push in
across the state with upper level ridging extending from the Gulf
of Alaska through the interior and up to the Bering Straight. This
feature will slowly shift eastward through the long term forecast
period being pushed by a broad upper level trough moving from the
Aleutians to the Arctic through the Bering Sea. As the system
traverses northward, gale-force gusts and moderate snow
transitioning to rain are expected for Southwest Alaska from
Thursday through Saturday.

Southerly onshore flow will bring moderately strong wind and
precipitation to the Eastern Aleutians Thursday before progressing
eastward to the Alaska Peninsula on Friday and finally across the
Southcentral coast through the weekend. Shortwaves moving through
the flow will enhance rains along coastal locations, with locally
heavy snow over higher elevations from the Alaska Peninsula to
Prince William Sound. Areas of snow in leeward locations like the
Western Kenai, Anchorage, and Mat-Su are possible at the end of
the forecast period, but downsloping will likely limit significant
accumulation.

A new system from the North Pacific will bring another round of
increased winds and precipitation to the Western and Central
Aleutians beginning Sunday morning.

&&

.AVIATION...

PANC...VFR conditions and light northerly winds will persist
through much of the TAF period. Cloud cover will move in this
afternoon and stay above 5000 ft. There is a slight chance for
light snow Wednesday afternoon, though some uncertainty remains.
Snow accumulation would be less than an inch.

&&


$$