Gale Warning 732, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
440 AM AKDT Wed Oct 23 2024

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

The upper level trough over the Arctic is moving east and is
positioned over the Beaufort Sea. Its trough axis stretches from
the northern ALCAN border through the central Alaskan interior.
Predominantly zonal flow prevails across much of the Bering Sea
and southern half of the state. Extending south of the Alaska
Range, weak embedded shortwaves are expected to move quickly from
west to east across Southcentral for roughly the next 24 hours.
The result will be persistent snow showers for higher elevations,
especially with upslope flow along terrain. Meanwhile, cold air
advection is expected to initiate a cooling trend for
Southcentral through the rest of this week. As colder air arrives,
on the developing westerly flow aloft, winds will diminish across
Cook Inlet but increase for Whittier, Seward, and other gaps
along the Southcentral coast.

Snow shower activity will likely diminish by this afternoon for
all locations with the exception of the central Chugach and
Wrangell Mountains. The next low arrives to the western Gulf from
the eastern Bering later Thursday afternoon. Where Kodiak was
being downsloped by westerly winds, a front will shift the pattern
completely, bringing rain and southeast winds to the Island for
Thursday through Friday. The front lifts north later on Thursday,
spreading precipitation across the northern Gulf coast and Prince
William Sound. The surface low and front look to remain far enough
south to keep most of the precipitation closer to the Gulf/Prince
William Sound coastlines with northerly offshore flow for much of
Southcentral. Broad Pass, Matanuska Valley, Thompson Pass, and
other coastal gap locations could become gusty with northerly
winds starting Thursday and potentially lasting through this
weekend.

Model consensus is reasonably good through the short term with
some slight variation beginning to emerge Thursday morning when
the surface low develops near Kodiak Island. The movement of this
low north- south will play a role in the strength of the offshore
winds through gaps, but also how far north precipitation will move
along the Kenai Peninsula Thursday and how much precipitation
Prince William Sound communities could recieve through Friday.

-TM/rux

&&
.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (TODAY THROUGH THURSDAY...)

A surface low pressure forming over the western Bering Sea this
morning will strengthen with strong mid-level and upper jet
support as it quickly moves eastward. The associated upper level
trough will dig southward across the Alaska Peninsula Thursday
morning with strong cold air advection across the Bering and
Aleutian chain. Coincident with modest pressure rises, an area of
storm force winds is expected on the backside of the low near the
eastern Aleutians/Alaska Peninsula, particularly near and just
east of Unimak Pass. Showers across these areas will become a more
steady rain late tonight into Thursday morning, possibly mixing
with snow at times.

After rain initially across portions of Southwest Alaska,
conditions will be cold enough to support mostly snow after for
coastal regions of the Bristol Bay area through Thursday morning.
There is still low confidence on the inland extent of
precipitation with this system, but up to 1 to 3 inches of snow is
possible along portions the Bristol Bay coast, including
Dillingham and King Salmon Wednesday night into Thursday morning.

Another low forming off the coast of Kamchatka Thursday morning
will push its front into the western Aleutians bringing a period
of rain. Rain chances continue through Friday as the system
lingers over the western Bering and additional moisture streams in
from the North Pacific. The entire system finally pushes eastward
through the Bering and through the Pribilof Islands and central
Aleutians by Friday evening. Winds with this front/system will be
weaker than today's, but a corridor of gale-force winds is still
expected.

-ME

&&

.LONG TERM FORECAST (FRIDAY TO NEXT TUESDAY)...

A deepening low in Bristol Bay Thursday moves over the AKPen and
into the North Pacific by Friday morning.  During its
southeastward progression, southwest winds and increasing wave
heights are likely along the northern AKPen and portions of the
Southwest AK coastlines. After it crosses into the North Pacific
Ocean, northerly storm force winds through the Central and
Eastern Aleutians are likely through Friday afternoon. Elsewhere,
high pressure in the North Pacific south of Adak will progress
southeastward Thursday as a front from a Kamchatka Low moves
through the Aleutians Saturday reaching the Southwest coastline
early next week. A second low begins to move through the Bering
Sea next Monday.

A low crossing into the North Pacific deepens as it progresses
into the Gulf of Alaska this weekend. During its southeastward
travel through the Gulf, increasing winds through Shelikof
Strait, Kodiak Island and the Kenai Peninsula can be expected.
Confidence in its exact placement is moderate with its
strengthening and eastward progression toward Southeastern
Alaska. As the low strengthens and progresses eastward, the
possibility of increased gap winds return for Price William Sound
for the end of this weekend into early next week. Elsewhere, as
the high in the North Pacific moves to the southeast, signals
point toward a weak low forming and moving northeastward along
the Aleutians toward the Northern Gulf of Alaska.

-JOHNSTON

&&
.AVIATION...

PANC...VFR ceiling and visibility persist. Winds subside through
the day and shift from southerly to northerly.

&&