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FXAK68 PAFC 300004
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
404 PM AKDT Tue Sep 29 2026

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

The forecast remains on track with only a few changes. The
shortwave trough that brought light precipitation to the western
half of Southcentral this morning has since lifted east-
northeastward over the Copper River Basin, allowing for clear
skies this afternoon for the northern Cook Inlet region. Panning
out, this wave is embedded within a broad longwave trough that
stretches from the western Bering to the eastern Gulf. Within this
longwave, a more robust shortwave now over the Bering will round
the base of the trough through tomorrow morning as a surface low
continues to develop downstream across the far northern Gulf.
Starting midday Wednesday, models have come into better agreement
overnight and this morning in regards to the surface low
placement, and the consensus now is that most precipitation with
be mostly confined to the eastern Kenai Peninsula and Prince
William Sound locations. The progression of the upper level wave
has more clarity this afternoon as well in regards to timing as
models have converged on the wave passing over the area Wednesday
evening. The overall weak flow with this system will lead to the
western fringes of precipitation propagating westward to encompass
Anchorage and the Matanuska Valley as well Wednesday evening to
early Thursday morning, and a sharp cutoff in rainfall extent will
most likely line up just west of Anchorage.

Precipitation type from Wednesday afternoon through Thursday
morning will be largely elevation dependent. For lower elevations
areas such as the Anchorage Bowl northward to the Matanuska
Valley, only a cold rain is expected as snow levels will remain
too high and temperatures only drop to near 40 degrees F for
overnight lows Thursday morning. With snow levels bottoming out
anywhere from 1300 to 1800 feet during the bulk of the
precipitation duration, higher elevation locations like Thompson
Pass, South Fork Eagle River, Upper Hillside, and the Talkeetna
Mountains are on track to see 1 to 3 inches of snowfall with
isolated 4 inch amounts. Locations lower in elevation like the
Anchorage Hillside, Rabbit Creek, Turnagain Pass, and Talkeetna
will most likely see a rain/snow mix as temperatures and snow
levels fall Wednesday night through Thursday morning. All said,
there is a good amount of cold air advection aloft associated with
the incoming trough, the coldest air of the season for most,
however, it appears that the coldest air does not arrive until
much of the precipitation is on its way out on Thursday.

The trough axis takes a negative tilt over Southcentral and
begins to lift out of the region late Thursday morning to midday
Thursday as the surface low skirts eastward. This will shift the
precipitation eastward toward Valdez and Cordova; decreasing
precipitation coverage to the west.

-AM

&&

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

Key Messages:

* Chance of marine lightning (10 to 20%) across the central Bering
  Sea this afternoon and evening and progressing to the southeast
  Bering Sea through Wednesday morning.

* Sub-freezing overnight temperatures move into Southwest Alaska
  throughout the week.

* A front brings rain and a corridor of gale-force winds in the
  western Bering Sea starting this afternoon for the rain and
  tonight for the stronger winds. This spreads eastward through
  Friday.


Discussion:

Current satellite imagery reveals a short wave digging
southeastward across the northwestern Bering Sea. There is a
strong 300mb jet streak accompanying this shortwave as well with
300mb winds approaching 130 kts. Cold air aloft and instability
will bleed in from the north as this feature works to the south
and east through Wednesday. With the unstable airmass associated
with this digging shortwave, a few lightning strikes are possible
(10 to 20% chance) across the central Bering this afternoon and
evening and across the southeast Bering through Wednesday morning.
A widespread lightning over water event is not anticipated. Aside
from marine lightning potential, the surface low associated with
the upper-level shortwave will also move from the north-central
Bering this afternoon and to the Alaska Peninsula (AKPEN) by
Wednesday afternoon. Rain will spread from the Pribilof Islands
this afternoon to the AKPEN this evening through Wednesday.

A follow-up shortwave, behind the initial shortwave causing the
potential marine lightning, drops down from Northern Alaska and
across mainland Southwest Alaska through Thursday. This feature
will bring cold temperatures across Southwest starting tonight and
lasting throughout the week. Daytime high temperatures will
struggle to get out of the 40s with nighttime/morning lows in the
20s. Due to cloud cover, temperatures across the AKPEN should stay
above freezing through the week.

Farther west, the Aleutians will see a front from a Kamchatka low
moving into the western Aleutians this afternoon, and pushing
the exiting ridge east. Nonetheless, showers and southeasterly
to easterly small-craft winds are expected to accompany the
front, especially in the western Aleutians with gale-force winds
to the north in the offshore western Bering zone. The low
eventually becomes elongated and catches up to the front Wednesday
night. Higher chances for precipitation spread to the eastern
Aleutians and eventually to the Southern AKPen on Thursday as the
low continues east. The area of gale-force winds also moves east
to the central Bering by Wednesday evening and Thursday as high
pressure builds across the northern Bering and Bering Strait
region. Gales become more confined to the North Pacific south of
Nikolski/Unalaska Thursday night into Friday as the Bering Sea low
transfers it energy to a new developing low in the North Pacific
by then. Aside from the gusty gale-force winds, rain works from
the Western Aleutians this afternoon eastward across the rest of
the Aleutian Chain by Friday morning.

&&

.LONG TERM FORECAST (Days 4 through 7)...

Looking ahead toward this weekend, models are synoptically in
good agreement in the midrange forecast, featuring a low moving
toward Kodiak Island from the North Pacific and another low into
the Bering Sea from the west. Precipitation with east to southeast
winds will be more than likely for Southcentral, especially
closer to the Northern Gulf coast and Kodiak Island. By Sunday,
the front extending from the Bering Sea low reaches Southwest
Alaska and the Alaska Peninsula bringing rain, snow, and southerly
flow across the area. As the low sinks southward Monday, models
diverge on how far south the low will dip. Generally, the low
appears to pass through the Alaska Peninsula and near Kodiak
Island/Western Gulf. As this pattern sets up through the first
half of next week, cold air advection and northerly winds will
become enhanced through gaps along the Aleutians. If the low sinks
south farther east, the Alaska Peninsula would see more cold air
advection and those northerly winds. While temperatures overall
for southern Mainland are trending cooler in the short term, some
moderation of that trend is expected toward more seasonable norms,
but will remain on the cooler side.

&&

.AVIATION...

PANC...VFR with light northerly winds expected. Precipitation
chances increase Wednesday morning between 12 and 18Z. Rain, and
potentially lower ceilings (around 1000 feet), should be brief
and showery, tapering off throughout the day.

&&

$$