273
FXAK68 PAFC 180027
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
427 PM AKDT Fri May 17 2024

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

A weak surface ridge will push north into the northern Gulf of
Alaska, bringing some breaks in the clouds and slightly warmer
temperatures to much of Southcentral on Saturday. Gusty
southeasterly gap winds, particularly out of the Turnagain and
Knik Arms and in the Copper River Basin will also develop ahead of
an approaching low and front. Cloud cover and upslope showers
along the coast will increase in coverage Saturday evening through
early Saturday night.

A strong low over Bristol Bay supported by a deep and
unseasonably cold upper level low over the Bering Sea will
strengthen as it pushes east over the Alaska Peninsula and over
Kodiak Island by Sunday morning, sending another period of
precipitation back into the island. As the upper low and
accompanying surface low move into the western Gulf, precipitation
will also overspread the eastern Kenai Peninsula and into the
Prince William Sound through Sunday morning. As the upper low hugs
the coast and moves inland, shortwaves on its western periphery
will allow precipitation to fill in over the Copper River Basin
late Sunday into Monday. The Eastern Kenai and Prince William
sound will see the heaviest precipitation while the Western Kenai,
the Anchorage Bowl and the MatSu will see lesser amounts with
drying downslope flow and gusty southeasterly gap winds.

-ME

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE ALEUTIANS
(Days 1 through 3: This afternoon through Monday evening)...

The forecast remains on track with the main player in the near-
term being a large upper-level trough that extends southward
through the Bering Sea. The upper-low within the trough will
continue dropping southward through the central Bering tonight and
into Saturday, bringing cold air with it as it does so. A stronger
short-wave rounding the base of the trough will induce
cyclogenesis on the Pacific side of the southern Alaska Peninsula
(AKPEN) tonight. This low will pull Pacific moisture northward and
into the AKPEN through Saturday. While most precipitation will
fall along the Pacific side of the AKPEN, the precipitation
forecast is a little more uncertain for the Bering side
communities due to southeast winds blowing across the Aleutian
Range and creating downslope drying.

Meanwhile, further north along the Kuskokwim Delta coast and
Nunivak Island, there will be enough cold air in place to create a
period of snow this evening into Saturday morning as the front
lingers across the southwestern mainland coast. Accumulations will
be light. This front pushes inland Saturday as the trough becomes
more negatively tilted. The main precipitation-type with the
system will be rain with northern areas of the Kuskokwim Delta and
Nunivak Island eventually turning over to rain as temperatures
warm during the day. The other story with this system will be the
easterly winds coming out of Kamishak Gap and impacting areas such
as Koliganek, New Stuyahok, and Iliamna with gusts up to 50 mph
Saturday and into Saturday evening. The main upper-low then
shifts to the Gulf of Alaska for Sunday with some weak shortwaves
left on the backside of the broad trough. This will help keep some
isolated showers going for interior portions of Southwest for
Sunday. Most of mainland Southwest clears out for Monday except
for some light precipitation confined to the higher terrain.

Further to the west, next weather-maker will be a Kamchatka low
and its front making their way to the western Bering by Saturday,
spreading small craft winds and rain along the western Aleutians.
The front will weaken as it moves eastward toward the central
Aleutians by Sunday. However, the trailing front will be a little
stronger with perhaps some more enhanced precipitation for the
central Aleutian Chain late Sunday night into Monday. The low
itself moves to the central Bering by Monday as the front sweeps
eastward to the Pribilof Islands, eastern Aleutians, AKPEN, and
eventually to the mainland coastline of Southwest by Monday
evening.

&&

.LONG TERM FORECAST (Days 4 through 7)...

A persistent northwest to southeast oriented longwave trough will
remain over the Bering with waves of lows moving into the
northern Gulf during much of the first part of the extended
period. This series of low pressure systems that move through the
Alaska Peninsula and into Kodiak Island will bring coastal rain
showers and interior cloudy and isolated rain showers. Toward the
end of next week, a stronger low pressure system will move
through Shemya into the Bering Sea and push the longstanding
trough eastward. Indications are that the persistent trough and
strong low could move in a more northeastward direction as high
pressure progresses northward through the north Pacific.

DJ

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through
Saturday morning. Gusty southeasterly winds out of Turnagain Arm
are expected to develop Saturday afternoon.

&&


$$