Gale Warning 247, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
528 AM AKDT Thu Mar 16 2023

.ANALYSIS AND UPPER LEVELS...

High amplitude ridge/trough pattern is set up over much of the State
and the Bering Sea. Cold air descending along the eastern edge of
the ridge sitting in the western Bering stretches across the
central/eastern Bering and across Southwest Alaska through the end
of the week. The complex system in the Gulf of Alaska has a series
of embedded mesolows and shortwaves. A developing low in the North
Pacific pushes into the Gulf of Alaska on Friday, and the trough
becomes negatively tilted. Flow will then transition to
southeasterly and will pull a good amount of moisture out of the
North Pacific towards Southcentral. Eventually the low will make
its way towards Kodiak Island, who will hold on to the north to
northwesterly flow.

&&

.MODEL DISCUSSION...

Models are in decent overall agreement thorough the next 48
hours. Beyond 48 hours, model spread begins to rapidly grow,
namely with a series of incoming lows developing in the North
Pacific. The 06Z NAM is showing better agreement matching the
timing of the GFS/Canadian as it tracks towards northern Kodiak
Island, but is still placing it further north, with the Canadian
furthest south and the GFS between the two. Model agreement
diverges again late friday night as the low pushes over Shelikof
Strait.

&&

.AVIATION...
PANC...VFR conditions and light winds will persist.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Thursday and Friday)...

An area of low pressure just off of Kodiak will be the initial
weather maker today. A weak, but noticeable, frontal boundary
extending to the east is bringing snow showers across the Gulf of
Alaska and into Prince William Sound. As this low lifts north and
dissipates this afternoon, so too will the front across the coast.
Some of the steadier and heavier snow showers will abate by the
early afternoon hours. Attention will then turn towards a low that
is developing deep in the Pacific. This low will lift north
through the day on Thursday and deepen to 980MB or deeper by
Friday morning, again, just east of Kodiak Island. A warm front
with this low is progged to drive north, and drape across the
southern Alaskan coast, dipping as far south as Prince of Wales
Island. High end gales force winds will accompany this front,
aiming for the Gulf of Alaska. Steadier and heavier snow will
spread over Prince William Sound tomorrow night. The heaviest will
start over the eastern Gulf and spread west by Friday morning.
For mainland coastal locations, precipitation type should should
flip from snow to rain by sunrise on Friday. The incoming stronger
winds with the front, coupled with the colder higher elevations
in Thompson Pass may lead to reduced visibilities from blowing
snow. Farther west, Turnagain Pass may encounter some blowing
snow, but with less intense winds. The morning hours on Friday
also present the next chance of snow for the Anchorage area at
large. Lower elevation areas from the airport, to downtown and
northeast through Palmer may get 1/2" of accumulation. Higher
elevations could see around 2". Around that time, winds along
Turnagain Arm and the mountains will pick up, quickly shutting off
any real snow chances. This also means that from Kenai to
Wasilla, and all areas west, should remain cloudy and dry. Models
start to diverge as another low will lift north this weekend, so
confidence quickly fades into Saturday. Regardless, the weeks of
sunny and blue will be on pause as we move into a relatively
active weather pattern.

&&

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

Offshore flow continues across Southwest Alaska, no significant
weather is expected.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Unsettled weather will continue across the eastern
Bering/Aleutians as cold air advection will continue to produce
ocean-effect snow. These snow bands will locally reduce visibility
at times. Otherwise, no significant weather is expected.

&&

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

The extended period begins with an retreating ridge in the
Central Aleutians being pushed out as a North Pacific low enters
the Western Bering/Aleutians. A complex of lows will be spinning
about in the Gulf, with multiple waves and lows showing potential
to bring precipitation across coastal Southcentral and Kodiak.
Confidence regarding the low's behavior in the Bering is moderate
to high, however in the Gulf there is much disagreement between
the models how the low complex moves. It can be said that a
generally unsettled pattern will persist through the remainder of
the weekend into the early week in Southcentral. Back out west,
the strong Pacific low will enter the Western Bering/Aleutians
Sunday morning and push northward to the Central Bering by Monday
morning. While the low advances northward, a front will sweep
eastward across the Chain. Starting Sunday morning in the Western
Aleutians, the front is expected to reach Nikolski by Monday
morning and Southwest Alaska by Tuesday morning. Following the
passage of the front along the Chain, mostly zonal flow is
expected with light showers possible. Additionally, by Tuesday
morning as the front reaches Southwest, potential for the front to
spin up a low at a triple- point is being investigated. This
system could bring amplified precipitation to Southwest Tuesday
and Wednesday, and the chance for a wave of precipitation coming
to Kodiak then coastal Southcentral Wednesday night into Thursday
morning.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: Western Gulf of Alaska, Northern Gulf of Alaska,
		 Prince William Sound, Barren Islands, Shelikof Strait, Cook Inlet
		 Heavy Freezing Spray Warning: Alaska Peninsula, Pribilof Islands,
		 Bristol Bay, Eastern Bering, Shelikof Strait, Cook Inlet
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KM
SOUTHCENTRAL ALASKA...SS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
LONG TERM...CL