Winter Storm Warning 1, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
505 PM AKST Sun Dec 31 2023

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
into next year)...

Nature deciding to kick things off with fireworks of its own with
an active pattern underway and for the foreseeable future.
Starting off first, an opening and weakening shortwave is making
its way inland this afternoon over the Kenai Peninsula, bringing a
mixed back of rain and snow overspreading the Alaska Gulf Coast
and up sloping over western portions of Cook Inlet. Temperatures
will gradually warm over the majority of southcentral AK through
the first half of the week with winds shifting more S/SE-ly as a
maturing low stalls due south of Kodiak Island by Monday evening.
This low eventually get absorbed into a second much larger and
stronger low tracking along the Western and Central Aleutian Chain
by Tuesday evening.

Precipitation-type (p-type) remains a challenge for Kodiak and the
north Gulf coast through Monday as the low stalls out southwest
of Kodiak Island. Still think it should keep air enough cold air
aloft for any precipitation to remain all snow except for the
lower elevations of the immediate coastline under ESE-ly wind.
Complicating matters further, will need to keep an eye on winds,
temperatures, and p-types by Wednesday evening for the Anchorage
bowl. With a strong E to SE-ly winds, anticipating downsloping to
keep much of the Anchorage and the Matanuska Valley dry or result
in light flurries during the day. However, as the attendant front
from the aforementioned strong Bering Low lifts up from the
south, with a surface high residing over the Arctic, expecting
some level of cold air to advect southward through the day on
Wednesday. As a result, best chances for a quick period of
potentially heavy snow would come on Wednesday afternoon into the
night time as the front lifts overhead with dense cold air at the
surface.

NM

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Today through Tuesday night)...

Offshore easterly wind flow across Southwest Alaska will increase
overnight tonight, and lead into a prolonged windy and gusty
pattern across Southwest into the mid work week. Rain and snow
showers across the Alaska Peninsula will continue through midweek
as a broad low pressure system in the Bering continues to send
active systems over the area. Over tonight, snow showers will move
north across the Southwest coastline bringing a 1-2 inches to
places such as Togiak up to Kongiganak. Locally higher snow totals
of 1-3 inches near Kipnuk and Mekoryuk. Snow showers are expected
to persist across Nunivak Island throughout the day Monday,
diminishing by Monday evening. Gusty winds coming through the
Kamishak Gap through Iliamna and Koliganek will become
increasingly strong from Monday and Tuesday, reaching peak
intensity by Tuesday afternoon.

By Tuesday afternoon, another new potent low moving into the
southern Bering Sea will push a strong front into Southwest,
effectively enhancing the already strong gradient and wind field
in place. Very strong gusts as high as 70 mph will be possible
with this next frontal system between Tuesday afternoon and
Wednesday morning, mainly where gap enhancement will again be most
prominent, roughly along a line running between Iliamna and
Koliganek. Additionally, over the marine areas of Bristol Bay,
near hurricane force southeasterly gusts will be pushing into
western Capes. Uncertainty for the exact strength and timing of
this next frontal system is still on the mild side, so be sure to
continue monitoring the forecast for updates as we continue to
hone in on this next impactful storm system.

CL

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 through 3:
Today through Tuesday night)...

Currently, the broad complex low pressure system across the
western Bering continues weakening, however the active pattern
across the Bering and Aleutians will be succeeded by a new
stronger system approaching early next week. For tonight, the
major system is a strong but weakening low pressure system pushing
northward from the southern Alaska Peninsula. This system is
pushing a wave of moisture, bringing a shot of snow showers across
the Alaska Peninsula into Southwest Alaska through the overnight
period tonight as well as mild gusty easterly winds up to 40 mph
near places like King Salmon. These winds and showers will likely
weaken slightly but continue until the next, stronger system
arrives Tuesday.

By noon Monday, a strong, storm force low will make it's presence
felt across the Aleutians as it approaches from the southwest.
Storm force easterly winds with gusts to Hurricane force will move
into the central Aleutians while temperatures initially remain
cold enough for incoming precipitation to fall as snow, possibly
resulting in near whiteout conditions at times for Adak and Atka.
The expected track of this low continues to shift west compared to
earlier projections, and this should allow warm air near the
low's center to make it into the central Aleutians and change snow
over to a rain/snow mix Monday evening before the low crosses the
Chain into the Bering and colder air rushes back in from the
northwest. Meanwhile, another strong low will move south of the
Alaska Peninsula, sending easterly gale force winds into the
eastern fringes of the Bering Sea close to the Alaska Peninsula
and Bristol Bay. This secondary system will merge with Bering
system's occluded front on Tuesday, eventually resulting in one
absolutely enormous low extending across much of the North
Pacific, Bering Sea and Mainland Alaska. Sustained winds between
gale and storm force range will affect most of the outlook area
around this system through at least Tuesday night, except right
near the center as it moves slowly east over the southern Bering
Sea.

AS/CL

&&

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

An active pattern is developing across the Bering Sea with two
strong upper lows to move through the region over the course of
the next week. The first upper low arrives early Tuesday, with
forecast guidance continuing to show potential hurricane force
wind gusts for portions of the Aleutians. The low will likely have
peaked by Tuesday afternoon, with a slightly weaker, but very
large upper low sitting over southern Bering from the start of the
long term forecast period on Wednesday through Thursday night. A
large wind field will see gales and storm force winds impacting
much of the Bering Sea with the potential for snow and blowing
snow from the Western Aleutians to the Eastern Aleutians. By
Wednesday the low's eastward progress will position the strongest
winds south of the Eastern Aleutians. Gale force winds gusting to
50+ knots will promote seas up to 35 feet on the Pacific side of
the Eastern Aleutians early Wednesday morning. Winds diminish into
Thursday with an axis of westerly gales stretching from north of
the Western Aleutians, southeastward across the Eastern Aleutians,
to the south side of the AKPEN. Attention then turns to the
weekend, where yet another strong low is forecast to emerge from
the North Pacific into the Aleutian Chain. This latter low does
not look to be as strong as the Tuesday low, but model discrepancy
abounds.

For Southcentral, Tuesday's Aleutian low will bring a stout front
into the Gulf of Alaska by Wednesday morning. This front will see
somewhat warmer temperatures associated with it, though with the
front already occluded the warm-up will likely be underwhelming.
Instead, expect to see a mix of rain and snow accompanied by gale
southeasterly winds moving across the Kenai Peninsula into Prince
William Sound through Wednesday afternoon. What have been largely
drier conditions across Southcentral will gradually transition to
a more unsettled pattern, with increasing snow chances across
Prince William Sound and the Copper River Basin. Precipitation,
while heaviest on Wednesday, will linger, especially along the
Gulf Coast, through early Friday. A second front arrives over the
weekend and closer to Sunday with renewed rain and snow chances
for Southcentral.

BL

&&

.AVIATION...

PANC..Conditions are expected to remain VFR around the airport
this afternoon and through the night as the next system moves
into the region. Southeast winds aloft moving over PANC will
continue to produce low level wind shear through this afternoon
into the evening.

CC

&&