Wind Chill Advisory 3, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
524 AM AKST Wed Jan 31 2024

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

Intermittent light snow has ended over the Anchorage and Mat-Su
Valley as the upper level trough finally lifts north into central
Alaska. Most of the associated cloud cover from this system has
eroded, but as skies clear this morning...the chance of fog
developing along the western Kenai Peninsula northward towards the
Mat-Su Valley will increase. This will play into low temperature
trends this morning as areas with clear skies have plummeted into
the negative teens and 20s while areas that are starting to see fog
and stratus are holding steady at near zero to around 10 below. This
will be the start to several very cold days as another push of cold
air moves in behind the departing trough. For most of Southcentral
(with the exception of the Gulf coastal areas and southern Kenai),
temperatures will struggle to reach near zero temperatures for the
next several days. Many inland areas may not see daytime
temperatures rise above the negative teens until Saturday or Sunday.
Surface high pressure will settle over inland Alaska tonight through
Friday and both Thursday and Friday morning look very cold for
Southcentral. The Susitna Valley and Copper River Basin look to see
the coldest temperatures with readings dropping to 30 to 40 below by
Friday morning. The Copper River Basin will hold onto the cold air
Saturday morning with temperatures once again dropping to near 40
below. With surface high in place, winds will remain light in the
Copper River Basin. For now...have held off on a Wind Chill Advisory
for the basin due to the light winds, but will need to keep an eye
on the potential. Thompson Pass is more likely to see the
combination of both cold temperatures and gusty winds as the gap
flow winds start to respond to the dense cold air and increasing
gradient. The one caveat to these cold temperatures will be any
cloud cover that works into the region helping to keep temperatures
from plummeting.

A weak front extending from a weakening low over Southwest Alaska
will push through the AKPen this morning. Kodiak Island may see a
period of light snow as the front moves through, but it should be
short-lived with little to no accumulation.

- PP

&&

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

The compact surface low that brought localized blizzard
conditions to the Kuskokwim Delta coast overnight is moving
inland this morning. Scattered snow showers and gusty winds will
continue through mid morning before conditions improve this
afternoon as the low weakens and the precipitation moves west
toward the Alaska Range. Temperatures are also rising as this
system moves inland; however, the very cold temperatures will
return in the wake of this low as the arctic airmass over the
interior drifts back over Southwest Alaska through the next
couple days.

For the Pribilofs, a stalled frontal boundary and developing
surface low will over the islands will lead to another round of
snow, blowing snow, and gusty winds today. 2 to 4 inches of snow
could fall through this evening, with the highest amounts across
Saint Paul Island. Most guidance has this boundary draped between
Saint Paul and Saint George, so while gusty easterly winds are
expected for Saint Paul Island today, gusty southwesterly winds
are expected for Saint George Island.

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 mix with rain, or changeover to all 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 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 and
blowing snow.

-TM/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...As light snow ends from early this morning and skies begin
to clear, fog will become the primary forecast challenge over the
terminal for the next few days. The environment is extremely
favorable for the formation of fog, and if fog does form, timing
its arrival and dissipation will be difficult. We will continue to
monitor trends and current conditions and will update the TAF
accordingly.

&&