Gale Warning 241, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
419 AM AKDT Thu Mar 13 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Thursday through Sat evening)...

A surface low south of Seward, frontal boundary across Prince
William Sound, surface trough over Anchorage, and an upper-level
wave (vorticity max) over northern Cook Inlet have all combined to
produce bands of snow showers from south of Cordova west to the
Anchorage Bowl this morning.

The heaviest snow bands overnight and into early this morning have
been along the surface trough and east of the upper-level wave,
from Portage, Whittier, and Turnagain Pass west to Anchorage. Some
bands produced snowfall rates of up to one inch per hours
resulting in 3 to 5 inches of snow from Portage Valley to South
and West Anchorage. As of 4am, the NWS office in West Anchorage
measured 3.7" of snow, the highest storm total snow since
November 15th, 2024 (117 days). The 4" snow depth measured at 4am
is also the most snow on the ground at the office since January
17th.

These bands will continue to slowly lift north and west through
the first half of the morning as both the surface low and upper-
level wave lift northeast. These snow bands, however, are not
expected to be quite as intense as earlier this morning, as the
axis of greatest moisture advection is also lifting north over the
Chugach Mountains. Still, an additional one to two inches of snow
cannot be ruled out this morning.

As these feature lift northeast, Cordova and Valdez will see
another round of showers. Rain may mix in with snow for Cordova;
however, it will remain cold enough for all snow with an
additional 1 to 4 inches of snow possible today. Snow showers will
also be likely for Seward today as the low lifts north and
a southerly flow develops in its wake.

A second, weaker surface trough and upper-level wave will move
from Kodiak to around Kachemak Bay this afternoon. The
southwesterly flow aloft will help draw moisture up over the
Western Kenai Peninsula as another vorticity lobe embedded in the
flow moves from Southwest Alaska over the Susitna Valley. The
result will likely be a band of snow stretching from Homer north
to Kenai and eventually Talkeetna. This band looks to set up just
west of Anchorage at this time; however, there is still some
uncertainty in the forecast.

The upper-level low then lifts north Friday morning, with the flow
aloft becoming more easterly. This will drive moisture and
precipitation along favored upslope areas of the eastern Kenai and
western Susitna Valley. The precipitation then diminishes for
these areas to start the weekend as the upper-level support wanes.
A shortwave will then quickly move from west to east across
Southcentral for Sunday with the chance for some light snow,
especially at elevation.

-TM

&&

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

The large low North Pacific low pushing its front through the
Aleutian Islands this week has become elongated and redeveloped
a more focused center south of the Alaska Peninsula this morning.
With this reorientation of the low, northerly winds bringing
cooler air from the Bering Sea across the Aleutians has allowed
snow to begin mixing back in with rain. The air mass cools
through the day as north to northeasterly winds around 20 to 30
kts continue, transitioning precipitation completely to snow by
this evening. At the same time, the bulk of the weakening front
sinks south of the Aleutians, meaning shower activity becomes
much more isolated in coverage.

Brisk northerly winds and air temperatures in the single digits
to 10s across the northern Bering Sea will lead to heavy freezing
spray close to the ice edge through Friday night before winds
diminish on Saturday. Southwest Alaska, meanwhile, enjoys clear,
cool and calm conditions amidst dry offshore flow and weak high
pressure aloft, until an upper level low drifting west across the
central Interior approaches the west coast for Friday. An
inverted trough over Southcentral Alaska shifts west across the
Alaska/Aleutian Range tonight, and the combination of the two
features leads to increased moisture and lift that spreads cloud
cover across Southwest Alaska. Close to the western Alaska Range,
sufficient instability for snow showers will lead to light
accumulations along an axis from Iliamna to Lime Village through
Saturday as the upper low lingers over the Seward Peninsula.

Shifting attention back out west, a new and much stronger front
pushes into the western Aleutians Friday night. Current
indications are that this will bring high-end gale force winds to
the western Bering/Aleutians, although gusts in storm force range
will be possible as the front advances eastward on Saturday
across the southwestern Bering and into the central Aleutians. By
Saturday night, the leading edge of the front reaches the eastern
Aleutians and Pribilof Islands. An initial mix of rain and snow
should transition to mostly rain for locations along the Aleutians
as warmer air moves in along and behind the frontal axis.

CQ/AS

&&

.LONG TERM FORECAST (Days 4 through 7 - Sunday through Wednesday)...

Conditions on the Alaska Weather map shows a rather dynamic set
of features, starting with an upper level trough from the Mainland
along the Southeast Panhandle which exits the region late Sunday.
A moderate amplitude upper ridge moves in and builds into the
Interior through Wednesday. Out west, a closed upper low inside a
broad trough moves from the Western Aleutians Sunday into the
Western Gulf of Alaska before dissipating into a trough over the
Gulf of Alaska on Wednesday. This arrangement keeps most of the
active weather across the Southern tier through the forecast
period. Model guidance shows good overall agreement through
midweek, with the Canadian model going light on the low that moves
over the Aleutians and Alaska Peninsula through Tuesday.

Weather remains fairly quiet over Interior Alaska until late in
the period. A well developed surface low in the far Western Bering
extends a front over the Aleutians and Bering through Monday,
bringing locally moderate rain and gusty winds along its track.
Areas of gale force winds are expected over the Western Bering
Sunday, diminishing. The front continues pushing into Southwest
Alaska, AKPEN, Kodiak Island and across the rest of Southcentral
Alaska to the Canadian border through midweek, with locally
moderate rain and gusty winds. Isolated areas of heavy rain are
possible along the AKPEN coast, Kodiak Island, the Eastern Kenai
Peninsula and Western Prince William Sound late Tuesday into
Wednesday.

- Kutz

&&

.AVIATION...

PANC... Mostly MVFR to IFR conditions, light northerly winds, and
snow showers will persist into the morning hours. A few instances
of LIFR are also possible early this morning in heavier snow
showers. Snow shower activity will taper off late this morning
with conditions returning to VFR. However, another round of
flurries or light snow showers is possible this afternoon into the
evening hours as another disturbance approaches the area.
Confidence in this round is a little bit lower in where the snow
placement will ultimately be; whether the snow band remains over
Cook Inlet or clips West Anchorage and the terminal. MVFR
conditions are possible if the band does end up clipping the
terminal late this afternoon into the evening hours.

&&