Tern Lake, Alaska Weather Forecast Discussion

449
FXAK68 PAFC 040050
AFDAFC
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 PM AKDT Fri Oct 3 2025
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...
Fairly quiet conditions continue across most of the forecast area
this afternoon as Southcentral remains under mostly westerly flow
downstream from a building ridge extending from the North Pacific
into the western Mainland. Mid to upper level cloud cover is
spilling over the top of the ridge and across the Alaska Range,
preventing some of the region from seeing a truly sunny afternoon.
Still, all but perhaps portions of the Talkeetnas will remain
precipitation-free through tonight. Unfortunately, the drier trend
will not last into the weekend.
By Saturday morning, a warm front associated with a large Bering
low pressure system will lift quickly north into the Gulf as the
ridge begins to shift off towards the AlCan and Southeast. Rain
moving along and ahead of the front will quickly spread from
Kodiak Island up into much of the remainder of Southcentral by
Saturday afternoon, particularly from the southern Kenai Peninsula
out to the Prince William Sound. Fairly robust but shallow
southeasterly flow will develop ahead of the front as a strong
coastal ridge develops along the Gulf coast, complicating the
overall rainfall potential in the lee of the Kenai/Chugach
Mountains. While this will lead to some amount of downslope drying
across the northern Kenai Peninsula out to Anchorage and the Mat
Valley, a deep fetch of moisture and southwesterly flow will ride
up into Southcentral above the layer of southeast winds developing
near the surface. Thus, expect at least intermittent periods of
light rain to make it to the ground across the Mat Valley and
Anchorage area starting by midday Saturday and continuing into
Sunday as multiple shortwaves lift up from the Gulf out of an
amplifying trough out in the west. Snow levels will also rise
quickly as warm air continues to stream north, pushing above 7000
ft from Saturday night into Sunday. This could lead to rises on
some area waterways over the weekend as recent snowfall over high
terrain melts and combines with runoff from periods of moderate
rainfall.
The other aspect to highlight with this system will be the strong
winds developing along the front and through mountain gaps farther
north. The front itself will begin to stall out as it approaches
the north Gulf Coast on Saturday afternoon as a gale force barrier
jet forms from near and just north of Middleton Island out to the
Barren Islands. To the north, southeast winds across the Kenai
Mountains and through Turnagain Arm will pick up quickly on
Saturday morning, then reach peak intensity sometime on Saturday
evening. The gradient will initially favor winds spreading into
much of the Anchorage Bowl, with widespread gusts as strong as 40
mph possible until winds abruptly shift south with a down-inlet
gradient developing by Saturday afternoon. Winds gusting up to 60
mph across the Hillside will persist into Sunday morning, as well
as along portions of the Turnagain Arm.
From Sunday night into Monday, a stronger shortwave trough will
move up past Kodiak Island and head towards the Kenai Peninsula as
a low forms ahead of it over the northern Gulf. Southeast winds
will shut off as the trough lifts through and erodes the coastal
ridge, shifting to westerly across much of the Gulf by Monday
afternoon. Steady rain will transition to scattered showers as the
profile becomes a bit more unstable with cooler air aloft moving
in with the upper low/trough, and snow levels will drop back down
to more seasonable thresholds around 4000 ft as the cooler air
mass filters back in.
-AS
&&
.SHORT TERM FORECAST SOUTHWEST ALASKA/BERING SEA/ALEUTIANS
(Days 1 through 3: Today through Monday)...
A low pressure system continues to move through the Bering Sea
toward the Bering Strait this weekend. A second low moves across
the Alaska Peninsula and over Bristol Bay Sunday. Short-lived weak
ridging builds into the Aleutians, AK Pen and Mainland to begin
the work week.
The low pressure systems moving through the Bering Sea remains
west of St. Paul as it travels toward the Bering Strait. This
storm brings heavy rainfall and strong winds to the Aleutians,
Alaska Peninsula and Mainland through Sunday. Storm force wind
gusts were reported for areas west of Atka today as the low moved
over the Aleutians. Gale to storm force wind gusts are expected as
far east as Nikolski as the storm moves west of St. Paul late
this evening. In the low`s wake, wind speeds diminish. Southerly
flow through gaps and passes range from 30 to 40 knots east of
Nikolski through Saturday afternoon from this storm. Winds
continue to increase through the day today for the Pribilof
Islands and the Mainland peaking tomorrow morning with gusts
ranging from 35 to 45 knots. The prolonged southwesterly to
southerly winds toward the Mainland will cause coastal impacts
with waves heights from 8 to 10 feet and high tide up to two feet
higher than normal from Kongiganak to Toksook Bay late this
evening into late tomorrow morning. Conditions improve beginning
tomorrow afternoon. Heavy rainfall will accompany the strong
winds though.
A second weaker low, forms Sunday morning just south of Cold Bay
and, drawn from the primary stronger low northward, crosses the
Alaska Peninsula Sunday morning and into Bristol Bay by the
afternoon. This second low brings increased winds through gaps and
passes in addition to another round of steady rainfall for the
lower Kuskokwim Delta Sunday and Monday. Elsewhere, weak ridging
forms for the Aleutians Monday bringing weak flow and the chance
of isolated rain showers with another storm by mid-week.
&&
.LONG TERM FORECAST (Days 4 through 7: Tuesday through
Friday)...
Southcentral will remain in a region of high pressure for much of
the long range forecast. With the exception of a trough through
Southcentral sometime during the middle to latter half of next
week, benign conditions are forecast. Instead, the focus will
remain west of the Alaska Range and across Southwest Alaska, the
Aleutians, and Bering Sea.
There have been hints in the long range guidance that Tuesday`s
western Bering low will be slower and deeper. Widespread showers
and strong winds will accompany the low`s front regardless, first
for the Western and Central Aleutians Tuesday morning, and then
for the Kuskokwim Coast and YK Delta Tuesday afternoon. There is
always some uncertainty with the long range forecast, especially
when it comes to nailing down timing and placement of impacts.
That beings aid, onshore flow remains forecast into the Kuskowim
Delta Tuesday and Tuesday night, which could coincide with high
tides to bring minor coastal flooding and erosion to the Kusko
Coast. Meanwhile, winds across the Western Aleutians are trending
stronger, with the potential to see southerly winds gusting up to
50 knots. The low and front depart Southwest Alaska and the
Aleutians Wednesday night
By the end of next week a strong Kamchatka low is forecast to
deepen with a broad front to push through the Bering and Aleutian
Chain with more showers and potential strong winds for the region.
BL
&&
.AVIATION...
PANC...Southerly winds will diminish late this afternoon.
However, after midnight tonight, a southeasterly Turnagain Arm
wind begins to move over the terminal bringing in wind gusts as
high as 25-30 kt by Saturday morning. Ceilings remain VFR above
5000 ft until the next front begins to move around noon Saturday,
when ceilings have potential to drop below 5000 ft with light
rain. Visibility is expected to remain VFR even when the rain
moves in. A period of LLWS is likely beginning between 1pm and 3
pm tomorrow afternoon as the SE Turnagain Arm wind at the surface
bends away from the terminal and down Cook Inlet while winds aloft
(around 1,500 to 2,000 ft AGL) at remain southeasterly around 25
kt.
&&
$$

NWS AFC Office Area Forecast Discussion