Gale Warning 202, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
440 PM AKST Tue Feb 20 2024

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

As a weakening low pressure system continues to make it's way
inland, gusty winds continue across many areas of Southcentral.
The low pressure system also brought a frontal boundary bringing a
wave a moisture into coastal Southcentral. Along with this
moisture, gusty southeasterly flow continues, with much of
Southcentral is seeing unseasonably warm temperatures. As such,
coastal locations experiencing precipitation are seeing largely
rainfall from this current system. Most active areas currently
will begin to see conditions diminish throughout the overnight
period tonight.

Late tonight into early Wednesday morning, a band of moisture on
the backside of this system is expected to wrap around, bringing a
wave of precipitation to the Kenai Peninsula, and to the Anchorage
and Mat-Su valleys. As this wave moves through, precipitation is
expected to be a rain/snow mix due to the near-freezing
temperatures at sea-level with a wet snow more-so at higher
elevations. However, this wave is expected to be fairly transient
with accumulations from Kenai to Palmer expected to be 0.1 to 0.5
inches of a rain/snow mix, coming to an end by the morning commute
hours. By the late morning Wednesday and into the early afternoon,
much of Southcentral will have a lull in winds and precipitation,
but may be soon to change.

As we approach the latter half of Wednesday into Thursday, a
large and robust upper low over the Bering Sea will push another
system into Southcentral, bringing a period of widespread
precipitation. This system will be notably colder aloft, so the
threat of moderate to heavy snow returns across portions of
Southcentral. This system is expected to bring another round of
gusty air to many of the same areas as are gusty currently.
Anchorage and the Mat Valley will see some gusty winds from
Turnagain Arm and Knik River Valley respectively. With gusty winds
coming out of these areas, there is the chance for them to bring
in warmer air. However a similarly cold push of air will be coming
up Cook Inlet at the same time. This is complicating the
precipitation type forecast for Anchorage, if snow will prevail or
if it will remain a rain/snow mix. For now, light accumulations
are expected in the Anchorage Bowl, with slightly higher amounts
up on the Hillside. The highest amounts will be in and near the
Chugach Range, with 1 to 2 feet of heavy wet snow possible in
Valdez and up to 2 to 3 feet in Thompson Pass late Wednesday into
Thursday. The Sutton area and northern Susitna Valley could also
receive upwards of 6 inches.

&&

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

Key Messages:

Snow for Southwest
* Winter Weather Advisory is in effect for the Kuskokwim Delta,
  including Bethel and Nunivak Island, from 3am tonight through
  Wednesday afternoon. Expect winds gusting as high as 50 mph,
  visibility reduced to one-half mile at times, and total snow
  accumulations of up to 2-3" inches.

High Winds for the Aleutians
* High Wind Warning is in 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 80 mph possible.

* High Wind Watch remains in effect for the Central Aleutians,
  including Amchitka, Adak, and Atka, from Wednesday afternoon
  through early Thursday morning. Expect southwest winds 40 to 60
  mph with gusts up to 70-80 mph possible.

Discussion:

Active weather remains on tap for Southwest Alaska out to the
Aleutians through the rest of the work week.

Out west, 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 night into tomorrow morning for the Western
Aleutians, with gusts up to 80 mph possible. As the low
progresses eastward, there remains the potential for the central
Aleutians to see sustained west to southwest winds up to 40-60mph
with gusts up to 70-80 mph gusts. However, the location and timing
for when those winds decrease is playing a factor in where the
strongest winds relative the Aleutians will be located, and if the
High Wind Watch in the central Aleutians will be upgraded to a
High Wind Warning.

An approaching front from the aforementioned low will bring snow and
increased winds across the Kuskokwim Delta and Bristol Bay areas
late tonight through Wednesday afternoon. As a result, expecting
this front to reach Southwest Alaska coast by tomorrow morning,
bringing yet another round of snow for much of Southwest. The
heaviest snow expected around Dillingham, Aleknagik, west to Togiak,
the windward side of the Kuskokwim mountains, and along the
Kuskokwim coast. Highest snow accumulations for the Lower
Kuskokwim Delta around 2-3" expected near Toksook Bay and Nunivak
Island. Less snow is expected inland near Bethel, but higher
winds in combination with blowing snow may cause significantly
reduce visibility down to around one- half mile at times. Given
increased winds and resulting reduced visibilities, a Winter
Weather Advisory has been issued for the Kuskokwim Delta for
tonight through Wednesday afternoon. Not anticipating a long
duration event as snow will gradually taper off through the
evening on Wednesday.

-VR/NM

&&

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

A complex low over the Bering will send a series of shortwave
troughs across the Aleutians and into the mainland Alaska through
Saturday. Quasi-zonal flow late in the week will begin to
transition to more meridional as a low deepens over the Gulf and
trough starts to dig into the western Bering. In between these
systems, ridging will become more amplified as it moves over the
Aleutian Chain before dampening out once it translates into the
Gulf. These disturbances will bring locally heavy precipitation to
much of the Aleutian Chain, AKPen, Southwest and portions of
Southcentral. Warmer temperatures on the Pacific side should allow
for more rain or a rain/snow mix with rain/snow to all snow to be
found on the Bering side where much colder temperatures will
reside. As these colder temperatures continue to push across south
and east, more areas will see precipitation change over from rain
or a rain/snow mix to all snow as the weekend progresses.

&&

.AVIATION...

PANC...The gusty southeast winds are expected to diminish later this
evening, but then return again Wednesday afternoon and continue through
Wednesday evening. Light rain will mix with snow at times later
this evening and then continue into Wednesday afternoon. No snow
accumulation is expected tonight or Wednesday with temperatures
mainly at or slightly above freezing near PANC. With the
persistent southeast winds, ceilings and visibilities are expected
to remain VFR through Wednesday. There is a chance for a brief
dip to MVFR conditions overnight as precipitation moves through
the area.

-CC

&&