Small Craft Advisory 899, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
516 PM AKDT Thu Oct 10 2024

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

The focus is shifting toward a strong storm that is currently in
the southern Bering Sea and moving towards the western Gulf of
Alaska. A stronger low with develop south of the Alaska Peninsula
toward the western Gulf and strength to high end storm force low
south of Kodiak. The initial front will cross Kodiak Friday and
continue to head to the north Gulf coast and bring in very strong
winds to that region as well. Gusts will be hurricane strength
with winds up to 75 mph. Some locations in the Barren Islands and
St Augustine could reach 80 mph. Shelikof Strait will be gusty as
well and some of the terrain gaps could enhance winds further.
This whole storm system is a bit chaotic and is unusually
difficult to nail down when and where the heaviest rain and
strongest winds will be. It does look like the main impacts will
be very strong winds in Kodiak (the high wind watch has been
upgraded to a warning for Friday) and the along the northern Gulf
to southern Cook Inlet for Friday. The coastal regions will also
see periods of heavy rain tomorrow. As the front moves inland
across Prince William Sound and the northern Gulf, winds will
decrease substantially. However, models are hinting toward
additional surface low development along the front over the
weekend, which could change the forecast details for various
locations of Southcentral. None the less, winds could be quite
strong along the coast and even become prolonged depending on
where and when another low develops at the surface. This could
pose a potential issue through mountain passes, such as Thompson
Pass, should enough cold air linger for a wet snow this weekend.
Plan ahead for more stormy weather and keep an eye out for changes
to the forecast.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Today through Sunday morning)...

A broad occluded low currently centered northeast of Atka is the
primary feature of concern through the weekend. Currently a broad
swath of high-end gales exists within the cold sector of this
storm from Shemya to just west of Nikolski, while the warm sector
is pushing through the Alaska Peninsula (AKPen) this evening with
breezy winds and rain. While the primary low center will fill in,
it will be replaced by multiple new centers developing within the
baroclinic zone along the front over the next 24 to 36 hours.
Models currently have one of these progged to develop over the
southern AKPen this afternoon, which can be seen beginning to take
shape on satellite imagery by a small kink in the cloud shield
along the primary cold/occluded front. This will become the
deepest low center for the overnight period, which will help to
amplify winds and increase the gradient to the north of the AKPen
and eastern Aleutians. As this drops south early Friday morning,
the strongest winds can be expected for the eastern Aleutians due
to cold air advection and an isallobaric component to the winds.
Meanwhile, an additional, and stronger low will develop farther to
the south along another triple point, before recurving up to the
north and performing the Fujiwara dance with the low that
developed overnight. Models have consistently placed this very
small, and deep low near Sand Point around sunrise on Friday. This
will once again tighten the gradients and bring the period of the
strongest winds to Bristol Bay and the Alaska Peninsula during
the daylight hours on Friday before it then drops to the south.
Winds will be the highest through channeled terrain on the south
side of the AKPen, particularly King Cove and False Pass.

For the precipitation aspect of this forecast, expect light to
moderate rain/showers from the eastern Aleutians through the AKPen
and into Bristol Bay. With the strong winds, this rain will likely
fall sideways and overall be an unpleasant day to be outside.
Despite relatively cold air aloft, the strong winds through
Kamishak Gap and downsloping off the Alaska and Aleutian Ranges
should keep sea level locations in the mid 30s to 40s and rain.

For Late Saturday and Sunday the influence of the low will slowly
wane, but breezy conditions will persist from the central Bering
east and throughout Southwest Alaska. Shortwaves moving north into
the Interior will also bring chances to areas of likely light snow
for the Kuskokwim Valley and Delta.

&&

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

The workweek opens with a well developed upper level closed low
over the Western Gulf of Alaska. Forecast confidence remains quite
high through the week. A reasonably clustered GFS/ECMWF/Canadian
composite hold through late Tuesday before an ensemble blend takes
over the changes in the pattern through Thursday. This low
weakens through midweek and dissipates into a trough entering
Southeast Alaska for Thursday. Strongest winds on the backside of
this low with areas of gale force gusts over the Eastern Bering
and Alaska Peninsula diminish over the North Pacific early
Tuesday. Areas of heavy rain move from Kodiak Island and the Kenai
Peninsula along the North Gulf Coast move towards the Canadian
Border by Wednesday. Higher elevations will see more snow. An
upper level ridge extends across the Northern Bering through the
week.

The moderately strong remains of Tropical Storm Barijat invade
the Western Aleutians late Monday. Some heavier rains and gusty
winds with areas of gale force gusts spread into the Central and
Eastern Aleutians through Wednesday before the low weakens and
drift back into the North Pacific to the South of the AKPEN by the
end of the period. Another upper level ridge stretches over the
Bering from the West through Thursday.

Kutz

&&

.AVIATION...

PANC...Predominantly MVFR/VFR conditions to persist through the
afternoon then VFR expected through the remainder of the period.
Northerly surface winds to remain under 10 kts through Friday
morning but increasing chances for windshear as easterly winds
aloft start to increase in response to system moving into the
western Gulf of Alaska.

&&