High Wind Watch 1, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
505 AM AKST Thu Jan 4 2024

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

A frontal system moving toward the Southcentral coast this
morning is bringing rain to the coast and snow from Cook Inlet to
the Copper River Basin. Snow is also falling at higher elevations,
with a focus on the mountains of eastern Kenai Peninsula and
Central Chugach. As the front moves north, a weak area of low
pressure along the front will move into western Prince William
Sound. This track will bring the strong southeasterly cross-
barrier flow to end and allow snow to fill in over the Anchorage
Bowl and Mat-Su Valleys as the gusty northeasterly winds subside.
Up to an inch of snow is possible from Kenai to Palmer and
Talkeetna through early Thursday afternoon. Similar amounts are
also possible across the Copper River Basin.

As the first system continues to move inland and weaken, a second
shortwave will move north from the western Gulf. This feature will
advect colder air aloft along with more moisture from the North
Pacific. The resultant increase in lapse rates instability will
drive bands of showers north over the Southcentral coast. With
temperatures hovering in the mid 30s, places like Seward and
Whittier will likely see a mix of rain/snow showers, with the
precipitation type driven, in part, by precipitation intensity.
Farther inland and at elevation, these showers will remain all
snow, with several inches of snow possible across the eastern
Kenai Peninsula from Turnagain Pass to Bear Creek. A similar set
up is likely for Prince William Sound, with Valdez likely seeing
several inches of snow and Cordova likely to see a mix of rain
and snow showers.

The bulk of the shower activity tapers off by late Friday, with
only scattered showers lingering across western Prince William
Sound. The frontal system moves from from the AKPen to Kodiak by
late Saturday. Southeasterly gales will develop across the Gulf
with gusty northeasterly winds returning for interior passes and
the Matanuska Valley.

-TM

&&

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

Our large low is centered just south of Saint George, where it
will remain today before heading off to the east towards Bristol
Bay. It will continue weakening before dissipating completely
shortly after making landfall over Greater Bristol Bay late on
Saturday. Overall, most areas across Southwest Alaska and the
Aleutian Chain have or will see improving conditions. Winds near
or at gale force will continue along the Central/Eastern Aleutians
today and then coming down overnight tonight.

Benign weather will continue through Friday morning before a
second strong North Pacific low pushes toward the Aleutian Chain
Friday evening. Like the most recent system, the front includes
high end gale force winds with areas of storm force gusts.
However, this system differs in a couple of ways. First, the
initial front is warmer and is likely to result in more rain
rather than snow along the Aleutians. Secondly, there is a good
pull of colder air from eastern Russia filtering into the
western/southern edges of the low. This is primarily affecting
wind speeds over the Central Aleutians on Saturday, with storm
force winds and a chance for hurricane force gusts at times.

&&

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

Active weather in the western portion of the state is expected
through the forecast period. On Sunday, there is model consensus
that a strong low pressure system will be over the Bering Sea,
with the frontal boundary extending into the Gulf of Alaska. As
the system moves northward, strong gale-force winds are expected
along the western Alaska coast. Temperatures will be close to
freezing, which should help reduce the chances of blizzard
conditions occurring along the west coast, however reduced
visibility at times with the system should be expected. As the
frontal boundary moves closer to the gulf coast, heavier
precipitation is expected along the coastline mostly in the form
of a rain-snow mix.

From the start of the week through midweek, a building ridge will
begin to settle into central Alaska, while a series of low
pressure systems will continue to impact the Bering Sea. While
there are inconsistencies with the strength and impacts of the
low, there is presently model agreement that the system will
traverse through the Bering late Tuesday into Wednesday. The ridge
over central Alaska should provide calm conditions during the
latter portion of the forecast period and beyond, and depending on
the strength of the ridge should help keep the Bering low farther
away from land.

BS

&&

.AVIATION...

A weakening front and upper level wave lifting up the Kenai
Peninsula this morning will support snow spreading into the
terminal this early this morning along with MVFR to briefly IFR
ceiling/visibility. Precipitation should clear out from south to
north by about midday (roughly 21z) and lead to return to
predominantly VFR conditions for the remainder of the TAF period.
However, there could be a short window for light freezing drizzle
early this afternoon after the snowfall ends as the mid to upper
levels dry out while a saturated layer holds on for a while longer
close to ground level. Surface winds will also remain light to
northerly, but southeasterly flow will increase later this
afternoon and evening aloft. There is some potential for marginal
LLWS to develop near the 2000 ft threshold as southeast winds
increase to around 30 to 35 kts near and above this layer starting
this afternoon through tonight.

-AS

&&