Gale Warning 43, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 PM AKST Fri Jan 10 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Sunday night)...

Key Points:

* The forecast is on track. A strong upper level jet stream will
  continue to steer two strong storm systems from the North
  Pacific to southern Alaska tonight through Sunday night, leading
  to widespread impacts to travel from wind and precipitation.

* For tonight, gusts in excess of 50 mph are anticipated for the
  East Anchorage Hillside, with winds peaking before 3AM. A Mat-
  Valley wind will promote northeasterly gusts ranging from 35 to
  45 mph through the morning hours on Saturday from Sutton into
  Wasilla.

* A High Wind Watch is in effect late Saturday night into Sunday
  for the Mat-Valley, Anchorage and Anchorage Hillside, as well
  the Eastern Turnagain Arm and Portage Valley. There is
  increasing confidence that the region is set to experience a
  damaging Chinook windstorm with the second storm system on
  Sunday.

* Coastal areas will see periods of heavy rain at lower elevations
  and heavy snow in the mountains. Inland areas will see much less
  precipitation, though there will be brief periods of
  precipitation spreading inland.

* Colder air will move in behind the second storm system Sunday
  night into Monday. All signs point to a shift in the overall
  pattern, with a return to more seasonable temperatures and
  chances of snow for Southcentral Alaska next week.

There are minimal changes to the previous forecast and much of
the previous forecast discussion remains the same. A deepening low
immediately south of the Alaska Peninsula will lift into the
western Gulf through the overnight hours as a negatively-tilted
trough. The trough remains forecast to bring gusty conditions to
Southcentral through the morning hours on Saturday as well as
widespread precipitation into the Gulf Coast and Prince William
Sound. Southerly flow associated with the trough will result in
warming temperatures to above freezing for much of the region.
Thompson Pass is expected to see a long duration of light to
moderate snow with periods of gusts as high as 45 mph. resulting
in blowing snow and reduced visibility and hazardous travel
conditions from Saturday morning into Monday morning.

Saturday's trough will be followed by a much larger and more
impressive upper low Saturday night into Sunday. All indications
point to a significant wind event across the Chugach, extending
from the Mat-Valley, down into Anchorage and Anchorage Hillside,
and further east into the Turnagain Arm and Portage Valley. Gusts
to as high as 70 mph will be possible at the lower elevations of
Anchorage while gusts to as high as 100 mph will be possible over
the Anchorage Hillside.

Aside from the wind threat, precipitation looks very heavy along
coastal areas Saturday night through Sunday. This could lead to
localized ponding of water or even minor flooding as rain falls in
the lower elevations. With such a dynamic set-up with high
atmospheric moisture content, expect precipitation to spread
inland Sunday, falling primarily in the form of rain. This will
soak into and remaining snow/ice covered roadways. As the storm
continues northward across western AK Sunday night and Monday,
Arctic air will wrap around the south side of the low across
southern AK, likely bringing a quick shot of snow before
precipitation ends. This looks like it will lead to larger shift
in the pattern, bringing an end to the prolonged period of warm
and windy conditions with little snowfall.

-SEB/BL

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3: Today through Monday night)...

A weakening low is centered over Nunivak Island this evening and
continues to push northeast producing scattered rain and snow
showers over the Kuskokwim Delta through early tonight. Along the
coast, southeasterly onshore winds gust up to 50 mph are expected
through early tonight, leading to potential for storm surge. The
main flooding threat occurs around high tide early tonight, where
water levels could reach up to four feet above the normal highest
tide line. The low weakens and exits into the northern Bering Sea
Saturday morning, allowing the coastal flood threat to subside.

A second storm-force low near Kodiak Island brings a front across
the Alaska Peninsula into Bristol bay tonight, spreading light
snow into the Kuskokwim Delta early Saturday. Some light showers,
mostly in the form of rain, are possible to the east of the front,
particularly in portions of Bristol Bay east of Dillingham. Warm
air has the potential to work in and turn snow to rain at times as
temperatures remain above freezing in Bristol Bay, though where
precipitation remains heavy it will likely remain snow. There is
potential for snow to persist for much of the night from
Dillingham west, which could result in snow totals of 2 to 4
inches, though most locations across Southwest Alaska will receive
closer to 1 or 2 through Saturday. The front lifts north across
Southwest Alaska on Saturday as some colder air works in behind
the exiting low and temperatures in the Kuskokwim Delta may drop
back into the 20s.

A third, stronger and larger low pressure system enters the
eastern Bering Sea from Saturday into Saturday night. Strong
southeast winds will spread into Southwest Alaska through the
Kamishak Gap into the greater Bristol Bay region along with rain
and snow moving back across much of the area as well. Northerly
gale force winds set up across the Pribilof Islands and eastern
Aleutians, bringing in a colder air mass from the western Bering
Sea. Much of the model guidance continues to situate the western
periphery of a front right along the Pribilof Islands, which leads
to significant uncertainty in the potential for low visibility
and blowing snow, with any westward shift in track favoring this
and an eastward shift making it virtually a non-issue. Confidence
is increasing in moderate snowfall, with around 6 inches of snow
accumulation possible for Nunivak Island and the Kuskokwim Delta
coast from Kipnuk north Saturday night into early Sunday morning.
Confidence is low at this time, but blowing snow/reduced
visibility may also pose a threat for these locations as well.

Eovino/Quesada

&&

.LONG TERM FORECAST (Days 4 through 7: Tuesday through Friday)...

On the Alaska Weather map, an elongated upper level trough
stretching from the Russian Far East across the Aleutians and
Bering. This trough gets a little boost from passing shortwaves to
reorient over Southwest Alaska and the Gulf of Alaska for
midweek, before continuing its Eastward track into Canada by
Thursday. An upper ridge building across the Western Aleutians
Tuesday moves to extend across the Gulf of Alaska and Western
Alaska into Northeast Russia through the end of the week.
Deterministic GFS and ECMWF carry the features and changes well
through Thursday with the Canadian models joining up into the
weekend.

A decaying surface low on the Southcentral coast spreads locally
heavy rains along the coastal locations, with locally heavy snow
further inland and over higher elevations through Wednesday. A
second low over the Shumagin Islands brings mostly rain with snow
over Bristol Bay from the Eastern Aleutians, Alaskan Peninsula and
Kodiak Island through midweek, before moving over the Kenai
Peninsula before dissipating over Prince William Sound Thursday.
Bands of snow progress across the Bering through Thursday. A well
developed North Pacific low and fronts spreads snow changing to
rain across the Western and Central Aleutians Wednesday and
continues over The Bering, Southwest Alaska and the AKPEN by
Friday. Gusty winds with gale force gusts work their way from the
Central Aleutians over the AKPEN and Bering through Friday.

&&

.AVIATION...

PANC...VFR will generally prevail through the TAF period. Low-level
winds will increase out of the southeast tonight in response to an
approaching low and its front. Have included low-level wind shear as
a result. Can't rule out a little bit of spillover rain tonight into
early tomorrow, but the best probability of any precip comes as the
wave lifts overhead, or between 21z and 00z. Ceilings may briefly
lower to MVFR as a result. As the wave lifts, this will also be the
best chance for gusty southeast winds out of the Turnagain Arm to
bend in Anchorage.

&&