Gale Warning 115, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
504 PM AKST Tue Jan 30 2024

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

Snow is coming to end for most places across Southcentral. A few
lingering snow showers continue for Prince William Sound
communities and along Kachemak Bay. All precipitation should be
coming to end though by Wednesday with the current system. A few
small flurries and fog is likely around the low lying areas along
Cook Inlet, including Anchorage, the Mat-Su Valleys, and Kenai.
The next system will move into the western Gulf and will bring
more snow, but will weaken as it moves east and is not expected
to move much more north than Kachemak Bay area and the southern
Kenai Peninsula through Wednesday morning.

Cold air will settle into place across southcentral Alaska from
midweek and into the weekend. Highs around or below zero and lows
well below zero are likely for much of the area outside of
immediate coastal locations along the PWS and Gulf of Alaska. As
northerly winds gradually increase Wednesday night and Thursday,
gap winds could be especially gusty and this will allow those gap
wind locations (such as Seward, Whittier, Valdez) to be almost ten
degrees warmer. Any clouds or fog formation of Cook Inlet fog/low
stratus could moderate temps a bit. That said, if conditions can
remain clear one of these nights, it's entirely possible ANC
records its lowest temp since 2009.

-Brown/Rux

&&

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

The most prominent feature tracking over the outlook area this
afternoon is a compact, intense low sitting near a strong thermal
gradient between an Arctic airmass sitting in place to the north
and east and slightly warmer air over the open waters of the
Bering Sea. This low's front is just beginning to move onshore
over Southwest, with southeast winds combining with falling snow
now starting to spread into the coastline to cause areas of
blowing snow. A Winter Weather Advisory remains in effect through
early tomorrow morning along the Kuskokwim Delta Coast, where the
worst visibility is expected ahead of the front with
falling/blowing snow overnight. The compact, gale force low
currently north of the Pribilofs will make landfall north of
Nunivak Island then rapidly dissipate as it starts to move inland,
with areas of snow following along the front over Southwest also
diminishing during the morning. Bitterly cold temperatures in the
-20s to -30s will also rise to the single digits above near the
coast on Wednesday, but much colder temperatures are set to
stubbornly hold in place over the Lower Kuskokwim Valley for the
next couple days.

Looking farther out ahead and at the broader picture, a change in
the pattern is set to take shape starting between Wednesday and
Thursday as a ridge builds in and sharpens over the eastern Bering
and AKPen while troughing develops near the western Aleutians and
begins to lift northeast into the southern Bering. This will allow
a southeast to northwest low track to set up along deep southerly
flow setting up between these two features, with a gale force
North Pacific low first crossing the Aleutians into the southern
Bering on Thursday. The developing southerly winds will also help
transport warmer air northwards with time, and this should help
areas of snow near the first system transition to mostly rain
along the central/eastern Aleutians by Thursday morning. Snow will
take more time to transition or mix with rain near the Pribilofs
where colder temperatures with the retreating Arctic air will hold
on for longer, and there could be periods of blowing snow and
reduced visibility near the first low's front lifting slowly
through between late Wednesday night and Thursday. Very strong
winds will also develop between a strong pressure gradient between
the incoming low and Arctic high pressure sitting over the
northern Bering, likely peaking well within storm force range west
of St Matthew Island between Thursday and Friday.

A second low and attendant front will push northeast across the
Aleutians into the southern Bering on Friday, producing another
round of southeast winds in high end gale force range and areas
of rain/snow along the Chain as it passes through. Meanwhile,
the remnant front associated with the first low will move into
Southwest, bringing returning chances for accumulating snow.

-AS

&&

.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...

An upper level closed low center over the Eastern Interior exits
into the Canadian Provinces for late Sunday. A moderate upper
ridge slides from the Eastern Bering across the Southern Interior
through Tuesday. These two features continue to pump arctic air
across most of the state. Another upper level low is working its
way across the Bering through the end of the forecast period.
Several significant troughs and fronts rotate around this Western
system, bringing periods of more active weather with each passage.
A well developed Eastern North Pacific low extends a trough
through the Eastern Gulf. The initial blended models slip smoothly
into the ensembles through the forecast period.

Between the approaching Eastern Gulf trough and systems pushing
over the Aleutians and Alaska Peninsula through the weekend, a
relatively steady warming trend spreads across Southern Alaska.
Rain will spread from the Alaska Peninsula, across Kodiak Island
and along the North Gulf Coast. Residual cold air should help
keep any precipitation as snow inland. Colder temperatures remain
an issue across the Bering as arctic air exits the Northern
Mainland through Southwest Alaska, and the Bering low draws frigid
air from the Russian Arctic. The Bering and Aleutians see a
return to active weather and can expect multiple fronts to bring
both rain and snow and gusty winds through the weekend. A strong
front extending from the Bering low comes with gale force winds
through the Eastern Aleutians and lower half of the AKPEN before
diminishing for Monday. The warmest air yet looks to arrive with
rain or freezing rain, both low probability, possibly reaching as
far north as Dillingham Sunday into Monday.

Kutz

&&

.AVIATION...

PANC...Although the main trough has passed, a couple trailing
short-waves could be just enough to produce some light snow
through this evening. The forecast challenge for the next two or
three days will then be fog. The environment is extremely
favorable for the formation of fog, so have made a large
adjustment to the 00Z TAF to add this in. Assuming fog does form,
timing of moving in and out of the terminal will be difficult.
Will have to monitor trends and adjust the TAF accordingly.

&&