701
FXAK68 PAFC 230057
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
457 PM AKDT Wed May 22 2024

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

Cool and cloudy weather continues across Southcentral Alaska this
afternoon as an upper-level low remains situated over Western
Alaska. An occluded front lifting across Southcentral this evening
will continue to bring moderate to heavy rain along the coast of
the eastern Kenai Peninsula and Western Prince William Sound.
While it appears, based on radar reflectivities, that some
moisture has been overspreading the mountains, only trace
precipitation (some light sprinkles) have been observed at the
ground from Anchorage north into the Matanuska Valley and southern
Susitna Valley. Despite the southeasterly flow, however, some
marginal instability in the atmosphere is leading to limited
downslope drying. Therefore, further south, a stronger feature - a
band of light rain showers lifting slowly up the (western) Kenai
Peninsula and southern Cook Inlet today - was able to drop one
tenth of an inch of rain in Homer. This feature will lift
northward this evening, reaching Anchorage and the Mat-Su Valleys
tonight. Similar amounts of rain as seen in Homer today are also
forecast for Anchorage, Eagle River, Palmer, and Wasilla.

While southerly gap winds through Turnagain Arm, the Knik River
Valley, and the Copper River Valley persist this afternoon, they
will diminish this evening as low pressure in the northern Gulf
shifts east and the current coastal ridge breaks down.

Heading into Thursday morning, the occluded front pushes into the
Copper River Basin, where limited cross-barrier flow will allow
for most places to see some limited rainfall accumulations.
Greater accumulations are likely north and east of Glennallen,
with over half an inch, up to one inch of precipitation, is
possible north of the Wrangell Mountains near Mentasta Lake and
Nabesna through Thursday night. Temperatures near freezing at
night in the higher elevations mean that snowflakes may be seen
down to approximately 2000` with some light snow accumulation
towards Isabel and Mentasta passes. For the Cook Inlet region,
Thursday appears much drier with ridging briefly moving overhead.
While some clouds are likely to linger around the mountains,
lower elevations are likely to see mostly sunny conditions.

This will be short-lived, however, as a low tracking into
southern Alaska from the Bering Sea will bring cloudier conditions
and another round of precipitation to Southcentral. Rain chances
return for much of the area on Friday, though the heaviest, most
persistent precipitation will occur along the north Gulf coast. A
front lingers along the coast, keeping these areas wet through
Saturday. Further inland, a shift to northerly flow as the low
tracks into the Gulf will lead to some drying and breaks in the
clouds heading into the weekend.

CQ

&&


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

This morning`s precipitation will continue to end this afternoon
in Southwest Alaska. A front associated with a Bering low will
move through the Western Aleutians this afternoon. It will reach
the Pribilofs and Central Aleutians late this evening and the
Alaska Peninsula/Southwest Alaska coast early tomorrow morning
bringing gusty winds, fog, low ceilings and precipitation.
Localized southwesterly wind gusts ranging from 35 to 45 mph in
the gaps are expected tomorrow morning into the early afternoon
hours in the Central Aleutians with gusts ranging from 20 to 30
mph elsewhere. Precipitation type will begin as rain this
afternoon but as colder air wraps around the backside of the
front, the precipitation in the Pribilofs, Central Aleutians and
points along the northern coast of Southwest Alaska (Kipnuk and
Toksook Bay) will be a mix of snow and rain showers this evening
and overnight. Little accumulation is expected though. The highest
QPF values are expected in the Goodnews Bay to Alaska Peninsula
area early to mid-morning tomorrow and in the Kuskokwim Delta late
tomorrow morning into the afternoon hours.

As the low progresses eastward reaching Nunivak Island tomorrow,
another round of precipitation will move through Southwest Alaska
from Togiak northward to Bethel tomorrow night before spreading
eastward into Aniak to New Stuyahok by early Friday afternoon.
Precipitation type is trending mostly rain though a few wet
snowflakes could mix in early on for some locations. Trends
continue to depict a mostly rain/snow mix for Toksook Bay/Kipnuk
areas during this late week event with surface temperatures
warming into the lower/middle 30s and temperatures at 850mb only
in the 20s. Widespread fog in Southwest Alaska is likely tomorrow
evening into Friday morning. Another weak low could move through
the Alaska Peninsula Friday night bringing widespread rain showers
to Southwest Alaska and the Alaska Peninsula through Saturday
afternoon.

-DJ


&&
.LONG TERM FORECAST (Days 4 through 7) Sunday through Wednesday...

A steadily weakening upper level low slips across the Southern
Gulf of Alaska through midweek. A somewhat energetic low in
Northwest Alaska transits along the West coast and weakens through
the period. A moderate amplitude ridge in the Western Bering
flattens out as it moves along the Aleutians by late Monday. Some
additional energy moves in with a weak upper low pushing over the
Aleutians through Wednesday. Model confidence starts off good in
GFS/ECMWF blends and run-to-run consistency, before making the
switch to deterministic guidance by midweek. Aside of showery
precipitation along the West Coast with the low moving Southward,
the bulk of the active weather will come with the surface lows and
fronts or troughs over the Southern portions of the state. Areas
of rain spread over the Gulf and Southcentral, diminishing through
Wednesday. Brief periods of locally heavy rainfall starts over
the Western Aleutians and Bering Sunday, moving Eastward into
Southwest Alaska, and across the AKPEN and Kodiak Island by the
end of the forecast midweek. The next system starts to repeat the
weather pattern in the West for Wednesday.

- Kutz

&&
.AVIATION...

PANC...Winds will once again be the biggest challenge through this
evening. Light early afternoon winds have veered southeasterly
again as a low in Southwest Alaska has the Turnagain Arm winds
bending back into the airport late this afternoon and evening.
What should be different tonight is that a front associated with
this low should pass through the Cook Inlet region which is
expected to shift the winds to a southwesterly direction and
diminish them late tonight.

When the winds do shift southwest, it will also bring in a period
of rain and potentially MVFR ceilings for the late evening
through overnight hours.

&&


$$