Gale Warning 838, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
534 PM AKST Sun Nov 17 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
The upper level pattern is a little less complex today as the main
upper low center has shifted into the Gulf of Alaska. Weak ridging
aloft is extending into the Interior from the Seward Peninsula.
Cold arctic air can be seen flowing off of the Mainland in
satellite imagery as cloud streets and open-celled cumulus over
the Gulf of Alaska. Gap winds have been going strong all along the
Gulf Coast from Shelikof Strait through Resurrection Bay and to
the Copper River Delta. The upcoming forecast will focus on
continued gap winds, shifting toward Valdez, colder air, and some
blowing snow along the Glenn Highway.

Clouds are diminishing across the Southcentral Mainland as drier
air impinges on the area which will set the stage for some of the
coldest minimum temperatures of the year so far. The coldest spots
will be the Willow area and Copper River Basin getting well below
zero. However, the Matanuska Valley wind is expected to get going
later tonight and continue through early Tuesday, which will keep
temperatures from bottoming out wherever the winds are elevated.

The arctic air entrenched across the area is the cause for gap
winds along the usual spots, but a disturbance dropping southward
on Monday will enhance these winds, specifically for the Matanuska
Valley and Valdez/Thompson Pass areas. The Mat Valley winds will
loft recent low density snowfall and reduce visibility around the
Glenn Highway on Monday afternoon/evening. For the Valdez area,
slowly increasing winds will have the potential to reach high wind
criteria (gusts greater than 75 mph) as conditions become more
favorable on Monday afternoon and evening. Winds will slowly
decrease in all areas from west to east Tuesday into Wednesday as
upper level ridging builds in from the west along with a warmer
air mass.

MTL

&&

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

As snow showers over the eastern Bering, Aleutians, Alaska
Peninsula, and SW Alaska coastline begin to wind down tonight,
bitter arctic air will begin to sweep over Southwest Alaska.
Additionally, as a weak North Pacific low moves away from the
western Aleutians, a ridge of high pressure will begin to build in
over the western Bering. This will continue to expand until it
reaches SW Alaska and the Alaska Peninsula on Tuesday.

Arctic air will flow into the Interior this evening through
Tuesday morning with many places in the Interior staying below
zero Monday afternoon through Tuesday morning. Guidance continues
to show the coldest air will be during the late Monday evening to
the late Tuesday morning hours. This will coincide with a mostly
clear sky too. Therefore, Tuesday morning's lows ranging from the
middle 20s to the middle teens below zero will be wide spread from
Aniak to Lime Village northward. Wind chills ranging from the
middle -20s to the middle -30s are expected during this time too
in this area. South of this line, including Bethel and
Dillingham, lows drop to the single digits above and below zero
will be common.

A ridge of high pressure moves over the Aleutians this weekend
bringing temperatures into the 40s, producing fog and rain
showers. This warm air moves over the Bering Sea, Alaska Peninsula
and Southwest by Tuesday afternoon quickly rising temperatures
into the 20s in the AK Pen, the 30s along the Southwest coast from
Goodnews Bay northward and above zero in the Interior. Widespread
fog over SW Alaska will be common, too. A brief wave of snow will
pass over the northern portions of the forecast area late Tuesday
into early Wednesday, though impacts should be minimal. On
Wednesday, a narrow but amplified trough on the far western
portions of the Bering will slowly crawl eastward, setting up a
band of rain and gale-force winds for the far western Aleutians.

-BS/DJ

&&

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

By Thursday, a high pressure ridge will be the dominate feature
across most of the state, with a north-south oriented axis running
through Southwest Alaska. This will bring northerly flow to the
southern mainland and southerly flow to the central and western
Aleutians. Warmer air aloft is associated with this feature, so we
are expecting the cold temperatures from the first half of the
week to give way to more moderate temps in both Southwest and
Southcentral. The Copper River Basin could be the exception here
and stay colder.

Tightening pressure gradients could bring moderately strong
southerly winds over the western Aleutians and central Bering Sea
on Thursday ahead of a North Pacific low that looks to enter the
Bering Sea Thursday night. This system will be pushed to the
northeast as it moves through the top edge of the amplified ridge.
The low should stay in northern Alaska, but there is some model
disagreement here about how much it will flatten out the ridge.
This will be something to keep an eye on going forward as a couple
solutions have this wave bringing its energy south of the Alaska
Range on Saturday night and digging through Southcentral.

Lighter winds and little precipitation are expected throughout
the long term outlook for most of Southcentral and Southwest
Alaska.

&&

.AVIATION...

PANC...VFR conditions will persist. Gusty northerly winds should
increase overnight and persist through Monday. The biggest
question is how strong these winds will get as the core of
strongest winds will likely be just west of the airport. Will
gusts remain around 25 kt, or could a few reach close to 35 kt at
times Monday.

&&