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FXAK68 PAFC 040409
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
809 PM AKDT Fri May 3 2024

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

Southeasterly flow and weak upsloping continues areas of light
precipitation mainly across Kodiak Island up through the eastern
Kenai Peninsula, with some light drizzle expected to occasionally
spill over the mountains into the western Kenai and Anchorage
Bowl through early tonight. A front associated with a large mature
low over the Bering will then push into Southcentral through
tomorrow. Strong southeasterly flow will result in downsloping,
dry conditions for much of the western Kenai Peninsula north
through Anchorage and much of the Mat-Su Valley. However, this
second system will bring rain a bit farther north than the
previous, with locations along the Prince William Sound expected
to receive periods of moderate to locally heavy rain (high
elevation snow) throughout much of the weekend.

As this front pushes into the area, a strengthening pressure
gradient will also allow strong southeast gap winds to increase in
intensity through tomorrow, particularly out of the Turnagain Arm
and Knik Arms and Copper River Basin. A few higher gusts are also
possible up on the Anchorage Hillside. Temperatures will remain
near climatological averages, with highs in the 50s for most of
the region and lows in the mid/upper 30s to low 40s.

The associated large upper level low with this system crosses the
Alaska Peninsula into the Gulf later on Sunday, with a weak ridge
building over interior Alaska. When combined with some weak upper
level shortwaves and marginal instability, a few weak/light
convective showers and/or thunderstorms may develop along the
foothills of the Wrangell Mountains/Alaska Range in the northern
Copper River Basin late Sunday afternoon into Sunday evening.

-ME

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA AND ALEUTIANS
(Days 1 through 3)...

Rain, snow and windy conditions to the Aleutians and Southwest
Alaska through the weekend. A Bering low will move in a mostly
westward direction reaching just south of the Pribilofs overnight
and Bristol Bay late tomorrow morning. As the low`s front
progresses northeastward this evening, today`s rain and mix of
rain and snow are expected to change over to all snow showers as
temperatures drop overnight. This switch to snow is aided by the
low`s placement just east of the Pribilofs by mid-morning
tomorrow, continued cool 850mb temperatures and cold northwesterly
air flowing into the region. Widespread light snowfall
accumulations in the AK Pen, Eastern Aleutians and along the
Southwest coast are possible. However, the precipitation will
switch to a more rain/snow mix to rain quickly through the day
tomorrow as temperatures rise. Cooler northwesterly to northerly
flow will keep the precipitation in the Aleutians mainly a
rain/snow mix this weekend. Winds in the Central Aleutians will
remain strong into tomorrow afternoon before slowly decreasing.
Northerly to northwesterly winds tomorrow evening and Sunday will
bring continued cooler conditions to the northern side of the
Aleutians, the AK Pen and Southwest Alaska as the aforementioned
Bering low crosses into the North Pacific. Freezing spray returns
for this weekend in response to the northerly and northwesterly
wind flow.


-DJ

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

The upper level closed low near St Matthew Island weakens slowly
and begins to move to the Eastern Aleutians and Alaska Peninsula
before stalling briefly near Kodiak Island through the forecast
period. The broad trough over the Bering makes inroads over most
of Mainland Alaska with the jetstream support and North Pacific
energy along the Southern portions continuing. Model confidence
becomes more uncertain through the weekend with a number of
troughs rotating through the pattern. The next significant weather
producer moves over the Western Aleutians beginning Wednesday
night as a North Pacific low and front moves across to the Eastern
Aleutians by the weekend.

Overall breezy conditions linger across the Aleutians and AKPEN
through midweek, becoming gustier Wednesday night in the West, and
spreading to the Eastern Aleutians for Friday. Gale force winds
across the Southern edges of the low remain South of the Western
Aleutians Wednesday and Thursday before diminishing. Rain spreads
over the Aleutians through the forecast. Above average rainfall is
expected to spread into Southwest Alaska, over the AKPEN into
Cook Inlet and Kodiak Island for Wednesday and extends along the
Eastern Kenai Peninsula across Prince William Sound to the
Canadian Border. Heaviest precipitation will occur in the coastal
zones, with lesser amounts spreading inland through Friday.


-Kutz

&&

.AVIATION...

PANC...VFR conditions will persist. Confidence is higher today
that the southeasterly Turnagain Arm wind will reach the ANC
airport by late evening today.. However, the forecast challenge
will be with regards to timing. The stronger southeasterly winds
aloft have been staying in the 4000 to 5000 ft mountain top level
and are expected to remain near this and not make it down to 2000
ft for true low level wind shear.

&&


$$