Westchester Lagoon, Alaska Weather Forecast Discussion

083
FXAK68 PAFC 160047
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
447 PM AKDT Mon Sep 15 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA
(Days 1 through 3: Tonight through Thursday)...
A large area of low pressure spanning the Gulf of Alaska is
pushing an occluded front inland over Southcentral Alaska this
evening. This front brought light/trace rainfall to Anchorage
earlier this afternoon, with measurable rainfall falling along
portions of the western Kenai Peninsula and Kodiak Island. With a
core of cold air aloft over the center, there is sufficient
instability, aided by upslope flow along the north Gulf coast, for
the development of strong rain showers with the potential for
isolated thunderstorms. As of 4 PM, lightning has only been
observed south and east of a line from Middleton Island to Kayak
Island, but there is non-zero potential for a thunderstorm as
showers approach the eastern Kenai Peninsula this evening. The
heaviest rainfall is expected to fall along the north Gulf coast,
with around 3 inches of rain forecast over the next 24 hours in
the vicinity of Whittier. Fairly strong cross-barrier flow will
limit potential for inland precipitation especially as the front
has already moved past the coastal mountains, limiting dynamic
forcing. Tonight, the core of the low tracks toward the Barren
Islands, which will lead to another round of shower activity
spilling over the mountains into the western Kenai Peninsula,
Anchorage, and Mat-Su Valleys. Though, rainfall amounts will
likely be in the hundredths of an inch for all but the
southwestern Kenai Peninsula, where rain shower potential lingers
into Tuesday. The low opens into a trough over the western Gulf
Tuesday evening and shower activity quickly wanes.
The next system will then lift across the eastern Gulf Tuesday
evening and makes it to the north Gulf coast sometime on
Wednesday. The track of the low has been refined somewhat, with
the low likely to make landfall somewhere between Cape Suckling
and Yakutat. Cross-barrier flow will be fairly light with this
system, meaning that portions of the Copper Basin can expect
rainfall to spread north late on Tuesday and continue into
Wednesday. There is some uncertainty in how far the precipitation
makes it, with eastern Prince William Sound likely to see rainfall
at some point on Wednesday morning, but how much and how long it
sticks around is not clear at this time. Western Prince William
Sound is more likely to remain completely dry. The low quickly
weakens Wednesday evening as it is shredded on the coastal
mountains and only light showers linger in the Copper Basin and
eastern Prince William Sound.
By Thursday, a triple point low develops along a front extending
off a Bering Sea low. The triple point low tracks into the western
Gulf and brings another round of rain and gusty easterly winds to
the north Gulf coast. Downsloping appears stronger with this
system, so inland precipitation is expected to be quite limited.
Quesada
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS (Days
1 through 3)...
The large, complex low in the southern Gulf continues to
influence the northerly winds gusting up to 20 to 30 mph this
afternoon across the Alaska Peninsula and Southwest Alaska. These
winds are expected to diminish through this evening as the low in
the Gulf weakens. Apart from breezy conditions and mid to high
level clouds associated with the low in the Gulf pushing west
across the Alaska Range, expect quiet weather across Southwest
Alaska to continue through the first half of the week.
The main focus of the forecast remains the ~975 mb low that has
pushed its way into the western Bering today. This system has been
as advertised with widespread high-end gales and storm force
gusts observed throughout the day today along its front in
addition to a swath of moderate to heavy rain. A potent shortwave
visible on satellite spinning up just to the south of the Aleutian
Chain this afternoon will help to maintain the strength of the
front as it progresses east across the Central Aleutians through
this evening. By early Tuesday morning, the front begins to
quickly weaken just before reaching the Pribilof Islands and
Eastern Aleutians as surface troughing becomes more elongated and
upper level dynamic forcing decreases. The parent low, still
spinning just north of the Western Aleutians, retrogrades slightly
to the west Tuesday and begins to weaken as it tracks east along
the Aleutian Chain.
Winds are expected to weaken to small craft or less while showery
weather continues through midweek across the Bering and Aleutians
as the upper level trough progresses eastward and digs south into
the North Pacific. Rain chances will continue heading into the
end of the week as a compact low emerges from the North Pacific
and aligns itself with upper level divergence from the digging
trough and subsequently deepens. The Bering low evolves more into
a complex low at this time as the compact low lifts towards the
Alaska Peninsula and Southwest mainland, keeping the region
unsettled through the rest of the short term.
&&
.LONG TERM FORECAST (Days 4 through 7: Friday through Monday)...
The active weather pattern continues in the extended forecast as
a broad upper-level low slowly moves over the Alaska Peninsula
into the Gulf of Alaska. West-to-east zonal flow over the majority
of the region will maintain the active pattern, however, diminish
the likelihood for highly impactful weather patterns. Confidence
is strong that by Saturday morning, a low pressure system will
become established over the northern Gulf of Alaska, bringing the
potential for heavy rain and strong winds to the Southcentral
coast. Depending on the low`s orientation, there is the chance for
a barrier jet to form along the marine areas of the northern Gulf
Coast early Friday. Through the weekend, rain is expected to
continue along the Gulf coast and into Southwest Alaska. Areas of
gusty winds through the southern gaps and passes of the Alaska
Peninsula and Eastern Aleutians that weekend as well, given the
persistent northwesterly flow in the area. In addition,
southwesterly upper level flow will bring the potential for rain
to move up Cook Inlet and into the Mat-Su Valleys.
-CL
&&
.AVIATION...
PANC...VFR conditions and northerly 5 to 10 kt winds will persist
through tonight. Rain showers will likely move back over the
terminal early Tuesday morning, with some slight lowering of
ceilings possible as rain arrives.
&&
$$

NWS AFC Office Area Forecast Discussion