Gale Warning 967, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
439 PM AKST Mon Dec 23 2024

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

Synoptically, a broad trough in the Bering Sea stretching
northwest to southeast will continue to rotate and bring a low
across Kodiak Island through this evening and a warm front to
Southcentral Alaska tomorrow afternoon/Wednesday morning.

Mostly dry conditions are expected for Southcentral Alaska
including Anchorage, Kenai and Palmer through mid-week with
temperatures in the 30s. Though gusts at Portage have ranged from
50 to 60 mph this afternoon they will diminish overnight.
Persistent northerly winds into Anchorage have kept these winds
from bending into the city.

Precipitation for Kodiak Island and the eastern Kenai Peninsula
with 12-hour rainfall amounts ending at 3:00 pm ranging from
0.20" to 1.00". After a lull in precipitation and areas of patchy
fog from this evening through tomorrow morning, rain returns to
Kodiak Island, coastal areas of the Eastern Kenai Peninsula and
Prince William Sound as a warm front moves through the Gulf of
Alaska. This front will change precipitation to all snow as it
moves into the Copper Basin though little if any accumulation is
expected. Colder air moves southward over the CRB, Mat-Valley and
Anchorage area mid-week. Mid-week, another low pressure system
forms at the end of the aforementioned trough. Though its exact
track remains uncertain, model consensus continues to show a more
eastward direction toward the Panhandle. Confidence remains low of
its track and impacts at this time though given the varied model
solutions of this low's placement over the past 24 hours.

&&

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

This afternoon, a layer of warm air aloft has finally cooled
enough to end the freezing rain, which has lingered across
Southwest Alaska for the past several days. Remnants of a low in
the Gulf will lift north as an open wave trough, bringing light,
mixed precipitation northwest across parts of Bristol Bay, and
falling as snow where surface temperatures are below freezing.

The front of a 945 mb North Pacific low is advancing eastward
along the Aleutian Island chain. A new low is expected to form
along the frontal boundary just south of or over the eastern
Aleutians and Alaska Peninsula by Tuesday afternoon. It will then
slowly track north and east and deteriorate through the week.
Ahead of the front and behind the low may see widespread gale
force wind and moderate to light rain through Thursday. Northerly
wind behind this low will bring colder temperatures across
comparatively warmer water. This could generate convective snow
showers for the Pribilof and Aleutian Islands, and increase the
risk of freezing spray for the eastern Bering, where water
temperatures are colder. The most likely areas for heavy freezing
spray are in coastal waters and beyond the ice edge from Cape
Newenham to St Lawrence Island through Thursday afternoon.

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

A broad trough extending from the Arctic down to the North Pacific
and Gulf of Alaska will linger into the weekend, along with
several surface lows swirling around the Alaska Peninsula and
Kodiak Island. Precipitation along the coastline will be mainly
rain, with snow likely over portions of interior Southwest as
bitter cold air dives in from central Alaska. A ridge will start
building in over the far western Aleutians on Friday before
situating itself close to the western coastline of Alaska late
Saturday. This will drive the main surface low eastward towards
the central Gulf, weakening as it does so over the course of the
weekend. From a temperature standpoint, expect a noticeable drop
in temperatures over interior Southcentral and Southwest as cold
air digs in to the north and west of the surface low.

Behind the previously-mentioned ridge will be a strong Kamchatka
upper level low/trough, with its front moving over the western
Aleutians and Bering on Saturday. Strong winds will be expected
along the front as it shifts eastward over the weekend. The
trough will extend southeastward towards the North Pacific on
Sunday as a ridge in Southeast Alaska and portions of western
Canada builds towards the interior. By the end of the extended
forecast period, the ridge and upper trough will be positioned in
a SE-to-NW alignment, with the trough residing over most of the
Bering and the ridge persisting over the interior. The Bering
trough will results in periods of precipitation over the Aleutians
and western Alaska coastline, with almost everywhere else in the
forecast area having relatively calm conditions.

&&.AVIATION...

PANC...VFR conditions will persist. A weak Turnagain Arm jet,
which currently bends strongly southward down the Inlet will shift
northward toward Fire Island and Anchorage overnight tonight as a
short-wave heads inland. However, Anchorage-Homer pressure
gradients will remain positive, meaning the stronger winds should
remain to the south of the terminal. There could be a brief period
where the wind direction shifts to southeasterly, but if so, the
wind speed should remain less than 10 kts.

&&