Gale Warning 557, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
442 PM AKDT Sun Aug 25 2024

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

A shortwave ridge over Southwest Alaska currently separates
troughs over the western Bering and eastern Gulf. The ridge has
brought sunny skies from Kodiak Island north through Broad Pass,
while the eastern trough has kept the Copper Valley and Sound
mostly cloudy with light rain showers. Moving into Monday morning
the western trough will slowly begin to move east, first bringing
high clouds and building a ridge of high pressure along the
coast. The coastal ridge and approaching low out west will slowly
increase gap winds through the typical spots (Turnagain, Knik,
and Copper Valley) ahead of another round of rain moving in Monday
evening. Most of the precipitation will be confined to the Gulf
coast and western Susitna Valley due to southeasterly flow, but
upper level shortwaves may help to mitigate downsloping and lead
to periods of rain for the Cook Inlet areas and southern Mat-Su.
For Tuesday and Wednesday, conditions will be steady to
intermittent light rain for much of the region as the upper level
trough parks itself overhead. Winds however, will gradually
diminish by Wednesday as the coastal ridge breaks down.

&&

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

High pressure is situated across Southwest Alaska this afternoon,
leading to fairly calm, quiet conditions. Much of the region
remains overcast or mostly cloudy, keeping high temperatures in
the low to mid 50s for most places. Some portions of Bristol Bay,
which have seen sun for much of the day have been able to warm
into the upper 50s. Quiet conditions will quickly come to an end,
however, as a broad low centered in the western Bering swiftly
tracks eastward tonight. The low pushes its front, which is
bringing southerly near-gale force winds to the central
Aleutians/Bering Sea and moderate to heavy rain to the Pribilof
Islands today, into Southwest Alaska tonight. As the front arrives
along the Kuskokwim Delta coast early Monday morning, southerly
winds shift southeasterly and intensify to gale force, with winds
gusting as high as 60 mph along the coast.

Despite similar meteorological conditions to last week's coastal
flooding, the quick eastward progression of the front will limit
the potential for storm surge to build. The strong astronomical
tide forecast in the morning hours of Monday will combine with a
slight surge to bring waters levels up to 1 to 2 feet above the
normal highest tide line for locations along the northern
Kuskokwim Bay coast from Kipnuk to Apokak Creek. The higher end of
the forecast water levels (near 2 ft) are most likely in the
communities of Kwigillingok and Kongiganak, with values closer to
the lower end (near 1 ft) expected elsewhere. Also note that water
levels remain high along the lower Kuskokwim River, so minor
impacts could also be seen along the lowest stretches of the
river, from Akiak to the delta. All in all, this is not expected
to be as impactful as the recent series of storms along the
Kuskokwim Delta coast.

Coastal communities can also expect a period of moderate to heavy
rain through the early morning hours but the front will weaken
rapidly on Monday as it moves inland, bringing winds down through
the day as well. Light to moderate rainfall continues through
Tuesday, reinforced by a shortwave driving into Southwest Alaska
on Monday night after tracking along the Aleutians. In total,
Southwest Alaska can expect half an inch to one inch of rainfall
from this system, with the greatest amounts focused along the
coast. Across the Bering Sea, cold air dropping southward on the
back side of the low will lead to a swath of gusty northwesterly
winds to gale force sweeping eastward Monday through Tuesday.
Gales diminish as they sink across the eastern Aleutians into the
North Pacific for Tuesday evening. Then, a compact, developing low
tracks along or just north of the western Aleutians Tuesday night.
There is some uncertainty in the track forecast and timing of peak
intensity, but generally expecting a tightly-wrapped storm force
low to track along the Aleutian Chain for Wednesday. If, as some
model solutions show, this low tracks just north of the islands,
gusty winds would be in a favorable westerly direction that would
bring high winds into Adak and Atka, but currently have low
confidence in this solution at this time.

Quesada

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

A Bering Sea low sweeping over the Aleutians mid-week could slow
down or stall over the Northern Gulf of Alaska as a ridge builds
just east of it in Prince William Sound. As the low stalls,
southwest wind direction Friday through Sunday could result in
continuous periods of rainfall for the Prince William Sound area.
The confidence in its track increased to moderate today despite
exact location confidence as low.

Southwest flow into the Gulf at the end of this week could bring
Atmospheric River moisture from Kodiak Island to the Prince
William Sound coastline. A more eastward trend of the
precipitation was seen today in the ensemble models.  Though
differences in the exact location of the heaviest rainfall and
amounts remain varied. That said, confidence is increasing that a
portion of atmospheric river moisture will be brought northward
by the slow moving/stalled low.

-DJ

&&

.AVIATION...

PANC...VFR conditions and light winds will persist. Monday
afternoon a light Turnagain Arm wind looks to develop and bend
into the terminal. There is some potential that some patchy fog
may develop across the area Monday morning, but overall
confidence in any fog impacting the terminal is low attm.

MTL/PP

&&