895
FXAK68 PAFC 041215
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
415 AM AKDT Sat May 4 2024

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

Today will feel much like a repeat of the last couple days for
southcentral Alaska in terms of weather. Southeast flow on the
east side of an eastern Bering upper-level low continues to push
moisture and rainfall into the coastal Kenai and Chugach
Mountains, with much of the inland areas remaining well in the
downsloped, dry zone. The exception to this is a bit farther away
from the downslope effect such the northern Susitna Valley where
some places have recorded in the neighborhood of a quarter inch of
rainfall. This precipitation is expected to taper off today as the
low shifts farther southeast.

Once again, strong southeast gap winds are expected to increase
in intensity later today, 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.

-Brown/ME

&&

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

A combination of rain, snow, and rain/snow mix will continue over
the mainland through the weekend with more rain inland and
rain/snow mix towards the coast. The story is also the same for
the Alaska Peninsula (AKPEN), the eastern Aleutians, as well as
the Pribilof Islands. The culprit of the active weather continues
to be a vertically stacked and occluded low pressure system
currently spinning in the eastern Bering Sea. This low will slowly
move eastward to the Gulf of Alaska by Sunday.

A reinforcing shot of cold air from Russia looks to intrude upon
the Bering for the beginning of the new work week with strong
northerly flow through out most of the Sea. An upper-level low
will drop out of the Bering Strait region and act as a vehicle to
aid in the driving of cold air southward to the central/eastern
Aleutians, Pribilof Islands, and AKPEN. Coastal southwest will
also see cold air advect in from off of the Bering Sea as well.
This will help to turn any rain/snow shower mix over to all snow
for Monday into Tuesday before warmer air tries to work towards
the coast for Tuesday. With this cold air episode for Monday and
Tuesday, expect most precipitation to be of the showery variety
with most of it being being confined to the Bering Sea side of the
AKPEN and eastern Aleutians. Finally, expect a renewed chance for
freezing spray across most of the eastern Bering Sea Monday as the
cold air really works in, with less coverage on Tuesday.

&&

.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. Southeasterly Turnagain Arm
wind returns for brief periods during the day across the terminal
area as the strongest winds aloft lift to the 3000 to 4000 ft
level and weaken through Saturday afternoon.

&&


$$