Gale Warning 78, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
458 PM AKST Mon Jan 15 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through
3/Tonight through Thursday morning)...

Conditions across Southcentral are largely calm and benign this
evening. Earlier fog responsible for quarter mile visibility from
Anchorage down into Kenai has lifted, at least temporarily.
However, a dense fog advisory has been extended through noon
Tomorrow. However, in anticipation of fog redeveloping later this
evening. If this were the only notable weather the next few days
things across Southcentral would be awesome for this time of year.
Unfortunately, this is not the case.

A building ridge of high pressure over the Bering is forecast to
expand into Southcentral through the end of the week. Beginning
tomorrow evening, a shortwave trough is expected to slip southward
and into the Gulf ahead of the building ridge, resulting in
increasing northerly flow and cooler temperatures. Gap winds will
become more prominent tomorrow night into Wednesday morning. A
high wind watch has been issued for Valdez and Thompson Pass in
anticipation of increased winds. Additionally, gusty conditions
will exist across all of the other usual gap wind vulnerable
locales. Seward, Whittier, the Copper River Delta, and the Mat
Valley should all experience gusts of up to 50 mph, even if the
higher gusts occur for only a short period. Otherwise, windy
conditions across Southcentral will linger into the second half of
the week.

Otherwise, dry conditions will prevail through the end of the
week. Any fog and stratus that impacts Southcentral tonight and
tomorrow should begin to clear out by tomorrow evening as
northerly flow increases across the region.

&&

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

A very benign pattern is expected to take shape over the Bering
Sea and Southwest as a strong upper ridge already in place over
the southern Bering Sea becomes even more amplified and shifts
slowly northwest through much of the upcoming week. For the
shorter term, a rapidly weakening cold front draped between the
central Bering and Norton Sound will make rapid progress east into
the Kuskokwim Delta later tonight as winds ahead of it quickly
diminish from 30 kts to 20 kts or less between the Pribilofs and
Kuskokwim Delta Coast. As the front moves onshore, a band of very
light precipitation will advance east and inland across the
Kuskokwim Delta late tonight into Tuesday morning.  The northern
fringes of the Lower Kuskokwim Valley will also possibly see a
short window for very light snow as the front brushes past later
on Tuesday morning. Mid to upper levels will stay fairly dry as
this front moves through with more moist low levels, and this may
favor some drizzle or freezing drizzle mixing in with snow at
times across the Y-K Delta early on Tuesday morning. Any icing
amounts should be no more than a trace, but communities across the
Kuskokwim Delta should still be wary of possible slick spots
forming on Tuesday morning.

Otherwise, the main story will be the very strong upper level
ridge that will expand across the entire outlook area between
Tuesday and Thursday. Winds as strong as gale force will develop
around the periphery of the ridge as shortwaves rotate around it,
including along and south of the Aleutian Chain and AKPen from
Monday and persisting nearly steady-state through Thursday. A
strong low level inversion will likely develop as temperatures
aloft gradually warm under the persistent upper ridging, while
temperatures at the surface change little beyond the cool down
behind the frontal passage across across Southwest on Tuesday
evening. However, at this time low stratus and fog do not look
especially favored with a fairly dry low level air mass, so much
of the region could be treated to a rare string of mostly sunny
days.

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

An upper-level ridge will be situated over Southern Alaska and
the Bering Sea, suppressing active weather across our region
through next week. While the high pressure is in place through the
remainder of this workweek, a clear and cool pattern will prevail
for most of Southcentral and Southwest Alaska. With the high
pressure system centered over Southwest Alaska, models are keying
in on some low pressure system originating from the Gulf of Anadyr
and the Northern Pacific to move up the western- most Bering sea
and ride the northern edge of the ridge into Western Alaska.
Pockets of energy are coming up and over the northern side of the
ridge, bringing up the winds across Southcentral and out of the
local gaps. Potentially strong and gusty winds with colder
temperatures will likely be the impact felt for Southcentral and
Southwest through the latter half of the week into the weekend.
Areas of outflow winds develop along the Alaska Peninsula and
Southcentral Coasts, with gale force gap winds through the Barren
Islands and Shelikof Strait and along the Alaska Peninsula Coast
into the Eastern Aleutians developing for Thursday and diminishing
Friday. Gaps such as Seward, Thompson Pass, and Matanuska Valley
will be feeling some gusty winds by Friday potentially diminishing
by the early weekend. Model solutions are suggesting an unusual
retrograde of the ridge, advancing the high pressure to the
northwest into the weekend. By Saturday afternoon, there is the
potential for a new low to approach coastal Southcentral from the
Gulf of Alaska, however uncertainty on this system remains high.
As the new low pressure system develops in the Gulf early next
weekend, the potential for moderate to heavy snow to return to the
Prince William Sound area by late this weekend into early next
week.

-CL

&&

.AVIATION...

PANC...Calm and variable winds will persist through the TAF
period. Conditions are favorable for fog development until winds
increase late tomorrow night and Wednesday morning. Fog could
move into the terminal at any time during the TAF period, dropping
vis and cigs as low as LIFR.

&&