Gale Warning 196, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
402 PM AKDT Sun Mar 12 2023

.ANALYSIS AND UPPER LEVELS...

High pressure over eastern Alaska is weakening as an upper level
trough slides across western Alaska this morning. Well ahead of
this trough are cirrus clouds that span from Kodiak to Nelchina.
Thicker clouds behind the cirrus will slowly move in. Some light
showers exist on the western side of the Alaska Range, but will
diminish as they move into the dry airmass across south central.
Intense cold air that is moving from the Bering Strait will
increase freezing spray intensity as air temperatures dip below
zero across the St. Matthews and Nunivak Island waters.

&&

.MODEL DISCUSSION...

At the synoptic levels, models are in really good agreement. Among
the main models, all are in agreement with the Aleutian chain high
pressure getting pinched to the northwest, before rebuilding over
the western Bering. A weak trough dropping south across western
Alaska will weaken tomorrow, before an upper level low dives in,
parking over Bristol Bay by mid week. The strength and extent of
the cold arctic air advancing in over the region remains locked in
agreement as well.

&&

.AVIATION...

PANC...VFR conditions and light winds will for a few hours this
evening. Northerly winds will become gusty into the evening hours.
Winds should peak around 30 kt by early Monday morning, before
slowly weakening into Monday's daylight hours.

&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Wednesday)...

A cold arctic airmass continues to advect southward across
Southcentral as various upper-level features traverse the area
from the north. Clouds returned today as an upper trough
approaches the region from the northwest. The trough will drop
southeastward into Cook Inlet and the western Gulf tonight before
tracking into the Pacific on Monday. Increased chances for light
snow accompany this feature, mainly along the Kenai Mountains and
western Chugach Range from tonight through early tomorrow morning.
A surface low forms over the Gulf tonight and Monday, and the
tightening offshore pressure gradient combined with cold air
advection supports the development of gusty north to northwesterly
winds. Winds will strengthen through tonight and then persist
through Monday. The strongest winds are expected Monday morning
through the bays and passes along the coast, especially near
Kodiak Island, Seward, Valdez, and the Copper River Delta. Skies
are expected to clear for a brief period on Monday afternoon as a
shortwave ridge builds in advance of a large upper low approaching
from the northwest. By Tuesday, the low is advertised to enter
the western Gulf while low pressure strengthens at the surface
near the Southcentral coast. Through Wednesday, winds will shift
east-southeasterly and chances for snow showers and accumulation
increase for western Prince William Sound and eastern Kenai
Peninsula.

&&

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

An upper-level shortwave continues to dig southward across
Southwest tonight with another quick on its heels. Cold air will
be pulled southward with the aforementioned shortwaves and lead to
a cooling trend in the coming days. Winds will also increase in
response to these features tracking through the region. The second
trough/shortwave will likely bring some light snow showers to the
Kuskokwim Delta on Monday afternoon, but the bulk of the
precipitation will be along the Alaska Peninsula starting Monday
night. Snow is expected to continue for the Alaska Peninsula
through at least Thursday with gusty winds that could produce
blowing snow that may reduce visibilities at times.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 3: Tonight
through Wednesday)...

High pressure continues along the northern and western Bering with
a trough extending into the central and eastern Bering. A
shortwave continues to drop southward from the north across
Southwest tonight, with a second shortwave/trough following soon
after. The first will be relatively benign with no major impacts.
The second will bring a swath of cold air and rounds of showers
across the southern Bering Sea and Alaska Peninsula. Continued
snow showers across the eastern Aleutians paired with gusty winds
could lead to blowing snow that may reduce visibilities at times.
Strong cold air advection will produce gusty conditions and
elevated seas in the northern and eastern Bering. The combination
of strong winds, cold temperatures, and building seas is expected
to lead to extreme vessel icing at rates of 4 cm an hour or
greater from late Monday night through Wednesday night for areas
in the northern and eastern Bering Sea. Conditions may persist
into Thursday or longer, so be sure to know before you go and
check back with the forecast for updates!

&&

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

Unsettled but largely benign weather is expected for the extended
period, with a general warm-up from chilly conditions in the
short-term forecast. The feature to watch will be a strong low
moving into the Western Bering/Aleutians late next Sunday,
bringing the potential for storm force winds.

Much of the long-term forecast through Saturday will be dominated
by a somewhat stagnant pattern, with a broad upper level low in
the Gulf and a ridge of high pressure over the Western Bering
Sea. The upper level low will help spur the development of
several surface lows in the Gulf, with considerable uncertainty
remaining in the track and strength of these individual surface
features. These lows will likely bring winds of small craft to
gale force to marine areas, with gusty northerly winds possible
across Southcentral (especially Valdez) as the pressure gradient
tightens between high pressure inland and low pressure offshore.
The Gulf coast can expect multiple rounds of snow through
Thursday, with a stronger plume of moisture bringing the potential
for coastal rain and inland precipitation for Friday and
Saturday. Given uncertainty with the track and strength of individual
lows, there is lower forecast confidence regarding the
timing/magnitude of winds and precipitation amounts.

Further west, light winds and little to no precipitation are
expected across the Western Bering and Aleutians due to the ridge.
The Central to Eastern Aleutians, sandwiched between the ridge to
its west and the low to its east, can expect brisk northerly winds
and snow showers gradually tapering off through Sunday. Mostly
dry conditions are expected for Southwest Alaska. By Saturday and
Sunday, an upper level trough moving east from Russia will weaken
and begin displacing the ridge. A front will sweep west to east
across the Bering Sea, followed by a strong low moving into the
Western Bering by Sunday night. This low could bring the
potential for storm force winds along the Western Bering and
Aleutians.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Kodiak, SW Alaska, Bering Sea
 Heavy Freezing Spray Kodiak, Cook Inlet, SW Alaska, Bering Sea
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SS
SOUTHCENTRAL ALASKA...AF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...NS
LONG TERM...KC