Gale Warning 538, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
503 PM AKDT Sun Sep 21 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Tuesday)...

An upper level low currently centered over the western Gulf
continues to rotate shortwaves across Southcentral, promoting wet,
dreary weather through tomorrow morning. Radar imagery this
afternoon shows persistent widespread rain along the coast along
with a band of precipitation rotating across the Susitna Valley
down through Cook Inlet towards Kodiak Island. As the upper low
nudges to the east in the Gulf, another shortwave and accompanying
surface trough lifts out of the Gulf for Monday morning into
Monday afternoon, bringing another chance for light rain across
inland areas. Northwesterly flow through the AKPen on the back
side of the low brings gale- force winds to the waters from the
Barren Islands south through Shelikof Strait through Tuesday.

The footprint of rain across Southcentral will gradually shrink
through Monday afternoon between systems, though showers should
still be expected for the northern Copper River and Susitna
Valleys thanks to a trough lifting up across the Alaska Range.
Similarly, rain will continue for portions of the Prince William
Sound and adjacent areas due to continued troughing in the Gulf
and moist upslope flow into the mountains.

Modest cold air advection associated with the arctic trough
digging across the Interior will bring somewhat cooler
temperatures to much of Southcentral AK by late Monday through
Tuesday, particularly to the higher elevations. Southerly flow
ahead of the next system in the Gulf increases the coverage of
precipitation across Southcentral for Tuesday, and may yield some
snow to some higher elevation areas such as Hatcher Pass and along
the Denali Highway, including possibly the Paxson / Summit Lake
area of the Richardson Hwy. Warmer, deep southeasterly flow across
the Gulf and Southcentral begins to dominate by Wednesday morning
as a large frontal system brings widespread rain to the coast
through midweek, while cross- barrier flow likely leaves much of
inland Southcentral downsloped and mainly dry.

&&

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

Tonight, a broad low pressure system in the Gulf of Alaska will
continue to pull gusty northerly winds through the southern Alaska
Peninsula favored gaps and passes. Showers to continue similarly
in this region tonight, while both rain and winds are expected to
diminish later tonight into Monday morning. The prolonged
northerly flow has worked to cool out much of Southwest Alaska,
depressing the overnight low temperatures, which are expected to
be near freezing for the next few mornings.

Attention then quickly shifts to what will soon become a powerful
low expected to move up from the North Pacific into the western
Bering Sea between Monday. By noon Monday, the low's occluded
front will reach the Adak and Atka islands, with a corridor of
southeasterly gales. Access to a deep tropical moisture tap is
expected to support locally heavy rainfall rates as the front
moves past from west to east. Progression of the front is expected
to be relatively quick, limiting rainfall totals to a quick inch
or less for just about any given location along the Chain through
Monday night.

From Monday night into Tuesday, a corridor of even stronger winds
wrapping into the southern side of the low will spread across the
entire southern Bering Sea and Aleutian Chain behind the low's
leading front. A sting jet curling southeast around the low,
coupled with additional support from multiple shortwaves
transiting along the Chain, will support a region of storm force
sustained winds. Storm force winds will arrive near Adak and Atka
by noon Tuesday. Peak wind gusts around this timeframe for
Shemya, Adak and Atka are between 55 and 70 mph. By Tuesday
night, the low center will reach the Pribilofs as it finally
begins to weaken, while high-end gale force winds persists across
much of the southern Bering and along the central/eastern
Aleutians. However, a shortwave in the upper levels of the low may
promote another push of storm- force winds down into the Nikolski
and Unalaska islands. These westerly wind core is currently
expected to move over Nikolski directly by early Wednesday
morning, with Unalaska on the periphery of the strongest winds.
This feature does have moderate uncertainty in the models so stay
tuned as we resolve the rest of this event. By Wednesday
afternoon, the low will weaken significantly and begin to move out
of the area, with a ridge building into the central Bering Sea
behind it.

-CL

&&

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

The latter half of next week will see a lingering trough over the
Gulf of Alaska while high pressure builds into the western
Bering. A strong pressure gradient between the two features,
situated atop the Eastern Aleutians and Alaska Peninsula, should
finally be weakening, with small craft to gale force northerly
winds to persist over portions of the Aleutian Chain Thursday and
Friday. Ongoing northerly flow into Southwest Alaska will also
help to usher in colder temperatures for the duration from
Thursday into Sunday with potential overnight lows dipping into
the upper 20s/low 30s for some locations.

Due to how far south ensemble guidance is putting the trough over
the Gulf of Alaska, Southcentral should be relatively dry with
the exception of the locations along the Gulf Coast and within
upslope flow over the coastal mountains. Similarly, the Bering is
also favored to be less wet while high pressure overspreads the
region, though low stratus and fog may prevail in the place of
precipitation. Elsewhere, southwest flow into the Western
Aleutians may maintain a chance for at least isolated showers
through the end of next week into the weekend.

BL

&&

.AVIATION...

PANC...Rain will become less prevalent overnight, but showers are
likely to continue. MVFR to IFR cigs and vis are likely to develop
again tomorrow morning with rain redeveloping. Winds will remain
light out of the north.

&&