Gale Warning 198, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
503 PM AKST Mon Feb 19 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Monday
evening through Thursday)...

A southerly flow and its moisture plume are directed towards
SouthCentral as its parent low, located south of the Alaska
Peninsula, drifts north into Bristol Bay and the Southwest before
breaking down over the interior Tuesday. This pattern will keep
warmer than normal temperatures across the region in place for
another day, with snow levels sitting around 1000 to 2000 feet
(rain, the predominant precip type below these levels). Gusty
winds have prevailed today as southeast-to-northwest aligned
valleys, including the Turnagain Arm wind, Knik Wind, and south
Copper River Valley wind, become favored under this pattern.
These winds have largely inhibited precipitation from falling
across their effected locations, though could see a light sprinkle
break through if winds diminish some. Otherwise, these Chinook
and gap winds are forecast to continue through the overnight hours
tonight and tomorrow before diminishing late Tuesday as the
aforementioned low breaks down.

The pattern begins to shift overnight Tuesday and Wednesday as
the front over the Gulf dissipates and its southerly flow shuts
off, bringing a cooling trend to Southcentral. Much of the
precipitation that falls across the region will transition to
snow, with south-facing and coastal mountains still receiving
quite a bit of snow.

A transition to more seasonable temperatures and increased
chances of precipitation arrive late Wednesday into Thursday as a
deep trough comes barreling into mainland Alaska, bringing colder
temperatures to the region once again. Mountain snow will have
tapered off across most areas by this time, through the eastern
Prince William Sound will continue to see increased snow amounts
across its mountaintops. Along area roadways, snow amounts will be
relatively light other than along Thompson Pass which will
receive snow rates of about 6 inches or so per 12 hour period.

-AB

&&

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

Key Messages:

* Winter Weather Advisory is in effect for the Lower Kuskokwim
  Valley, including Sleetmute, from 10pm this evening through
  Tuesday afternoon with additional snow accumulations of 4-8 inches
  expected.

* Winter Weather Advisory is in effect for Bristol Bay, mainly from
  Dillingham north and west and around Port Heiden, from 10pm this
  evening through Tuesday morning with additional snow accumulations
  of 4-8 inches expected and wind gusts up to 40mph between Kokhanok
  and Koliganek.

* High Wind Watch will go into effect for the Western Aleutians,
  including Attu, Shemya, and Amchitka, from Tuesday afternoon
  through Wednesday. Anticipate southwest winds 50 to 70 mph with
  gusts up to 85 mph possible.

* High Wind Watch will go into effect for the Central Aleutians,
  including Amchitka, Adak, and Atka, from Wednesday afternoon
  through Thursday. Anticipate southwest winds 40 to 55 mph with
  gusts up to 80 mph possible

Discussion:

Active weather remains on tap for Southwest Alaska out to the
Aleutians through the rest of the work week. First up will be a
deepening low pressure located over Bethel, which is expected to
continue northward towards St. Lawrence Island through Tomorrow
morning. As this low traverses north, expecting a band of moderate
to heavy snow to develop roughly on a line from Port Heiden to
Dillingham then north to Sleetmute by late tonight through
tomorrow with forecast snowfall totals around 4-8inches. The
heaviest snow will fall overnight through early tomorrow morning
before becoming lighter during the afternoon. For locations east
of the Dillingham / Port Heiden line, snow will likely mix with
rain, limiting snow amounts. A corridor of gusty gap winds up to
40 mph is expected between Kokhanok and Koliganek by early
tomorrow morning.

Out west, the hits keep coming as a High Wind Watch has been issued
for Tuesday afternoon through Wednesday for the Eastern and Central
Aleutians as a deepening Kamchatka low starts to develop and shifts
eastward. Expecting this low to approach the Western Aleutians with
increased winds starting tomorrow mid-afternoon. Highest winds are
expected by late tomorrow night into Wednesday morning for the
Western Aleutians, with gusts up to 80mph possible. As the low
progresses eastward, there remains the potential for the central
Aleutians to see sustained west to southwest winds 40-55mph with
highest gusts up to 80mph by Wednesday afternoon.

-NM

&&

.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...

The upper level low in the Bering weakens and begins an easterly
track through Interior southcentral Alaska. It forms a weak
center over the Gulf Sunday morning, and dissipates by Monday
morning. The tightest gradients remain along the Southern
periphery propelled by a generally zonal jetstream. Transient
fronts and troughs will bring locally heavy precipitation across
the Aleutians, AKPEN and Southwest Alaska. Precipitation will be
mostly rain on the Pacific side, with mixed rain and snow or all
snow on the Bering side through Friday. Temperatures cool back
below freezing over the weekend, expanding the areas of snow
through Monday. After a shortwave ridge transits the Bering,
another upper level low moves out of the Russian Far East.

-ER

&&

.AVIATION...

PANC...Gusty southeasterly Turnagain Arm winds are expected to
persist across the terminal through Tuesday. There may be a brief
lull in these winds later this evening into early Tuesday morning
as the overall wind field bends more down inlet as the next in a
series of surface lows deepens south of the Alaska Peninsula. Any
lull in the southeasterly surface winds would likely introduce
LLWS to the terminal as strong southeasterly winds remain over the
Anchorage Hillside. Ceilings will lower to around 5,000 ft through
this evening, but should remain VFR. There is also the chance for
very light rain this evening if winds do subside.

-TM

&&