Gale Warning 140, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
517 PM AKST Mon Feb 26 2024

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

A triple point low has formed slightly south than modeled over
eastern Kodiak Island this afternoon, and is expected to lift
slowly north/northeast just off the southern Kenai Peninsula coast
through Tuesday morning. As the low moves northeast, its front
will slide over the northern Gulf coast with widespread
precipitation and easterly storm-force winds. While total snow
accumulations will be slightly less than previously anticipated,
snow and strong winds will still develop for the eastern Kenai
Peninsula with the strongest winds for Whittier and Portage late
Monday. Snow will also likely become heavy in intensity at times
across these locations, as well as Turnagain Pass, Monday night
through early Tuesday morning as the low begins to drift south and
the flow aloft becomes northeasterly. A Winter Weather Advisory
is in effect for Portage, Whittier, and Turnagain Pass from Monday
afternoon through Tuesday morning where gusty winds will create
areas of blowing snow and reduced visibilities.

Gusty northeasterly winds will also ramp back up through Thompson
Pass as the front approaches. The combination of winds and light
snow will likely bring reduced visibilities through the pass late
today into Tuesday morning. The western Kenai Peninsula will also
see a significant increase in northerly winds through the rest of
the day today. These winds may resuspend snow already on the
ground, causing areas of blowing and drifting snow from Kenai
south to Homer. Gusty winds in the Mat Valley are also expected to
continue through late tonight and slowly diminish throughout the
day tomorrow.

Northerly gap winds along the coast along with a reinforcing shot
of colder air will return to Southcentral late Tuesday through
the end of the forecast period as this system moves southeast and
exits the region. Temperatures will fall well below average for
the end of February. Wind gusts could reach 45 to 60 mph by
Wednesday morning for Seward, Whittier, and Valdez, and up to 65
mph for Thompson Pass.

-ME/TM

&&

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

A mature low pressure system that brought wind and snow to the
majority of continues its influence late into this afternoon. The
low will begin to weaken and cross the Alaska Peninsula tonight, a
development that will bring a general decrease in impacts across
Southwest Alaska throughout tonight. Communities along the Alaska
Peninsula likely to see snowfall tonight and some gusty winds as
the low tracks across the area. Periods of blowing snow are
possible, however due to some higher temperatures and terrain
blockage, conditions are not expected to be as impacts as the
currently ongoing impacts in mainland Southwest.

Following the departure of the low pressure system to the south,
winds will shift increasingly northerly tonight and becoming more
gusty by Tuesday morning. With the departure of the low pressure
system, northerly flow will become the dominant pattern across
Southern Alaska and for Southwest, will lead to increasingly
colder temperatures. Overnight low temperatures in the Lower
Kuskokwim Valley are expected to reach 0 to -10 degrees F tonight,
and will continue to drop into the week. Arctic air will fill
Southwest beginning tonight and continuing to flow steadily in the
rest of the week. This cold, dry air will bring clearing skies,
allowing for even colder overnight temperatures due to radiational
cooling. As cold air begins to flow more regularly into Southwest
from the north by midweek, winds will become more gusty,
especially through north- south orientated gaps and out into
Bristol Bay and the southern side of the Alaska Peninsula. Gusts
to 45 mph through terrain, and even in surrounding areas gusts to
30 mph will accentuate the feeling of cold air, so prepare for the
cold appropriately. This cold, clear, dry, and gusty regime is
expected to hold steady over mainland Southwest Alaska and the
Alaska Peninsula into the end of the work week at least.

By Wednesday morning, a polar low will develop in the northern
Bering Sea, diving southeast toward the Pribilofs. The system is
expected to intensify rapidly, and move into the Pribs by late
Wednesday morning. This system is currently advertised by the
models to bring gale-force winds with about another inch of new
snowfall, beginning Wednesday morning and persisting into the
mid-afternoon. However, we have observed these systems over-
performing the model expectations in the past, so a round of
blowing snow and reduced visibilities will be a focus of the
upcoming forecasts.

Simultaneously Wednesday morning, the leading edge of a north
Pacific low's front will push into the westernmost Aleutians.
Gale-force winds, as well as a round of initially snowfall
transitioning to mixed to plain rain is expected through the day
Wednesday, persisting and spreading north and eastward, reaching
Adak by Wednesday afternoon. Throughout the day Thursday the front
is expected to continue pushing across the Bering, reaching the
Pribs and Nikolski by late Thursday afternoon.

-CL

&&

.LONG TERM FORECAST (Days 4 through 7)...

In the wake of a weak ridge through the Aleutians, unsettled
conditions will dominate the long term period as a Bering low
moves through the region. Models remain in disagreement of its
exact track however strong winds are likely in the Central and
Eastern Aleutians. Cold air over the interior brings a return to
unseasonable temperatures to Southcentral and the Copper River
Basin late this week and into the weekend with lows in the -20 to
-30 range for the interior and -20 to -10 for Southcentral. Highs
will struggle to reach the teens during this time in Southcentral
and the Copper River Basin.

-DJ

&&

.AVIATION...

PANC...VFR conditions are expected through the prevailing period.
Light northerly winds will begin to increase Monday night with
a period of windshear this evening as southeasterly winds above 1
kft increase faster than northerly surface winds. A period of
flurries or light snow may move into the terminal but no snow
accumulation or impacts are anticipated.

&&