High Wind Warning 15, NWS Anchorage, AK

405 
WWAK72 PAFC 151351
NPWALU

URGENT - WEATHER MESSAGE
National Weather Service Anchorage AK
451 AM AKST Wed Nov 15 2023

AKZ187-151500-
/O.EXP.PAFC.HW.W.0015.000000T0000Z-231115T1400Z/
Central Aleutians-
Including the city of Atka and Adak
451 AM AKST Wed Nov 15 2023

...HIGH WIND WARNING WILL EXPIRE AT 5 AM AKST EARLY THIS
MORNING...

Gusty west winds will slowly diminish this morning. Occasional 
gusts between 60 and 70 mph will remain possible for the next few 
hours, but higher winds are not expected to continue.

$$

For more information from the National Weather Service visit
https://weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
539 AM AKST Tue Nov 14 2023

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

Generally quiet weather is expected for much of southcentral Alaska
on Tuesday. Satellite imagery shows the low that brought yesterday's
snow has now pushed into SE Alaska and Yukon. Meanwhile, the next
system to bring rain/snow into the area is now moving across the
Bering Sea near the western Aleutians. The otherwise quiet weather
in between has resulted in nearly clear skies, which in turn has
allowed freezing fog and low stratus to develop and expand through
the Susitna Valley and northern Cook Inlet, including Anchorage.
With limited radiational heating and mixing this time of year, along
with little horizontal air movement, fog may be quite slow to erode
through the day.

By late afternoon today, the warm front extending out from the
Bering low will bring rain (high elevation snow) and increased wind
to Kodiak Island and adjacent islands. This front will eventually
work its way northeastward through the Kenai Peninsula and into
the greater Anchorage area during the overnight hours. Snow is
expected at onset for most locations with lingering cold air in
place. Intensifying low- to mid-level SE flow will create a bit of
a precipitation / downslope hole for Anchorage and portions of
the western Kenai on Thursday, as well as slightly warmer
temperatures. The biggest forecast challenge will be in the
vicinity of Prince William Sound, such as Whittier, where
lingering cold air will be slow to scour out, but onshore flow and
relatively warm sea surface temperatures may promote a low-level
temperature profile more suitable for rain rather than snow.
Initial thoughts for Whittier and the coastline is that snow is
expected at onset, but a changeover to rain is likely with
continued onshore flow. Should a conversion not occur, one to two
feet isn't out of the question for Whittier, where nearly 2 inches
of liquid is expected by Friday morning.

High-resolution model guidance is indicating rather strong Turnagain
Arm and Hillside + South Anchorage winds for Wednesday, with gusts
exceeding 40mph possible. This will have to be monitored closely as
trees and other structures already have a high snow load on them.
High wind may cause some snow to blow off in some cases, but may
bring higher stress to some structures or vegetation.

By Wednesday evening, the downsloping will diminish across the
Anchorage Bowl, allowing precipitation to fill back in as shortwave
troughs lift through the area within the deeper trough as it swings
through Mainland Alaska. Precipitation-type remains tricky from late
Wednesday through the first half of Thursday as low-level air hovers
in the lower 30s. All in all, precipitation during this timeframe
looks limited. Even if all snow were to occur, most areas
wouldn't receive *too* much more snow. Colder air begins to filter
into the area late Thursday into Friday, allowing any rain or
mixed precip to change back over to snow. Additional snow accumulation
up to a couple inches is possible from Anchorage through the Mat-
Su Valley By Friday morning.

-Brown

&&

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

A strong, maturing low is making a final approach to the southwest
corner of the Bering Sea this morning, with a recent scatterometer
pass detecting a swath of sustained storm force winds south of the
center, or a ways southwest of Shemya out in the North Pacific.
This low is expected to move steadily into the Bering Sea during
the next 36 hours or so, eventually making landfall near the
Kuskokwim Delta as it weakens to gale force on Wednesday evening.
The low's occluding front and a supporting southwesterly jet
streak currently visible on satellite over the Bering Sea and
Aleutians will meanwhile make rapid progress northeast, reaching
the Southwest coastline by tonight, then moving quickly inland as
it begins to shear apart over the higher terrain of the Alaska
Range and Kuskokwim Mountains.

This system will bring with it a variety of hazardous conditions,
ranging from strong winds and high seas moving across the southern
Bering Sea and along the Aleutian Chain, to possible high surf and
coastal erosion along the Southwest coastline. The main impacts
the Aleutians will come first, with the core of storm force winds
expected to move near and south of the low as it heads east-
northeast, progressing from the western Aleutians this morning to
the eastern Aleutians by midday Wednesday. Gusts to Hurricane
force will be possible as this core of strong winds shifts east,
namely across the central Aleutians where a High Wind Watch for
gusts up to 80 mph remains in effect starting later this evening.
The stronger winds will weaken somewhat as they shift into the
eastern Aleutians and the low's central pressure begins to rise,
but areas between Nikolski and Dutch harbor should still be on
alert for gusts between 60 and 70 mph as the strongest winds move
through on Wednesday afternoon.

Attention then shifts to Southwest, where concerns are increasing
for the possibility of a prolonged period of strong, onshore winds
behind the frontal passage starting later tonight. Prior to this,
expect a band of moderate snow to reach the coast along and ahead
of the front later this afternoon, then move quickly inland
overnight tonight as the front continues northeast. Strong warm
air advection and deep, southwesterly flow behind the front should
very quickly push temperatures above freezing and change snow over
to rain, limiting snow accumulation to a few inches at most for
the majority of Southwest through Wednesday. More notably, the
overall trend for the front's parent low has been for a slower and
more northerly track. This will put much of Southwest under a more
prolonged period of gusty, onshore winds than previously
anticipated, and the potential for high surf and coastal erosion
from tonight through Wednesday night has increased as a result.

Looking briefly at the remainder of the forecast period, the low
should finally move inland as winds across Southwest and the
eastern Bering Sea turn northwesterly and begin to subside
between Wednesday and Thursday. Much colder air will also begin
to shift back into place as northwesterly flow drags Arctic air
into place behind the low and upper trough moving over Southwest,
turning rain showers back over to snow showers by early Thursday
as temperatures drop from above average to below average by
Thursday night.

AF/SS

&&

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

The long term forecast period begins on Friday with a cooling
trend anticipated. Light to moderate snow should be ongoing across
the Copper River Basin and portions of Prince William Sound,
east, as an upper low shifts into Southeast Alaska into Saturday
night. The bigger story is an expected trough drifting into
interior Alaska. Which will pull a broad swath of colder
temperatures in from the north. At the same time a drier air mass
will help to clear out most precipitation for both Southwest and
Southcentral through the weekend. The exception will exist over
the Bering where isolated to scattered snow showers are forecast
with the trough's passage. A Kamchatka low then brings a strong
front into the Bering Sunday into Monday with potential high winds
as the front moves through the Western and Central Aleutians. The
front will progress into the eastern Bering by Monday with a
rain/snow mix and enhanced southerly winds along the front, from
the Eastern Aleutians up into the Chukchi Sea.

BL

&&

.AVIATION...
PANC...Low stratus and/or fog with IFR conditions is likely
through this morning, but low confidence as to whether it will
move over the terminal. Otherwise, expect VFR conditions through
this afternoon. The next chance for snow with lower clouds and
visibility will occur late tonight around midnight, but as
southeast winds pick up through Turnagain Arm Wednesday morning,
snowfall chances will decrease over the terminal. Expect winds to
remain light and variable through the TAF forecast period.

&&