661
FXAK68 PAFC 200030
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
430 PM AKDT Sat Apr 19 2025

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

Clouds continue to linger across interior Southcentral this
afternoon as an elongated upper-level shortwave drops south across
the Copper River Basin. Persistent cloud cover over the Cook Inlet
and Mat-Su regions are beginning to erode this afternoon as the
upper level ridge upstream builds over the western half of
Southcentral. Isolated to widely scattered afternoon showers are
still expected this afternoon and evening along the western
facing slopes of the higher terrain, especially along the
Talkeetnas and Wrangells, as daytime heating aids in increasing
instability.

On Sunday, the interior areas will get their turn to bask in the
sunshine as the ridge slides east. Southeasterly gap winds will
also be on the increase Sunday afternoon for the typical locations
like Turnagain Arm, Knik River Valley, and Copper River Valley as
a coastal surface ridge builds out ahead of an approaching
frontal system. Elsewhere, an occluded front moves into Kodiak in
the morning, spreading rain into the Kenai Peninsula by Sunday
afternoon. Clouds will also move from southwest to northeast
through the day as the ridge gets pushed off to the east by the
approaching trough. This trough will move into Southcentral on
Sunday, bringing widespread light rain and mountain snow to just
about everywhere by Monday afternoon. Rain/snow totals will be
quite light.

This system continues to track east Monday afternoon through
Tuesday with the area of more widespread precipitation lingering
for eastern Prince William Sound and the central Chugach
Mountains. Farther west, showers taper off from the Kenai
Peninsula north through the Mat-Su valleys.

&&


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

As of this afternoon, short-lived high pressure is centered
across the Southwest Alaska mainland. Just about everywhere in the
western domain is experiencing some degree of warm air advection,
with the strongest for locations such as Atka and Nikolski, and
enhancement on the leeward side of the Aleutian Range due to
downsloping. All of this is due to a broad, weak area of low
pressure located just north of Amchitka with its attendant front
draped across the Pribilof Islands southward into Unalaska and
King Cove. The stout southerly flow is ushering in warmer air and
allowing temperatures across coastal and immediate Southwest this
afternoon to warm well into the 30s. Looking west, rainfall and
elevated winds associated with the front are currently impacting
the Central and Eastern Aleutians, with some gap wind gusts
surpassing 30 kts in Cold Bay. Looking farther northwest, a
secondary area of low pressure is taking shape in the western
Bering Sea.

Heading into Sunday afternoon, the GFS shows the primary low
being absorbed into the secondary low as the latter evolves into a
complex low pressure system, with a trough of low pressure
encompassing most of the Bering Sea. At the same time, what is
left of the front of the first low and its precipitation moves
towards Southwest Alaska. For the Kuskokwim Delta and Nunivak
Island, temperatures will likely be cold enough for snow that
could add up to an inch or two of accumulation before temperatures
moderate and rain mixes in late Sunday. Some of the guidance is
also hinting at a few flakes making their way southward into
Togiak, but temperatures will be marginal to support snow mixing
in and lasting longer than a few hours as warmer air continues to
spill into Coastal Southwest. Out west to the Western and Central
Aleutians, westerly flow, associated with the complex low
aligning with upper level energy, could support some light rain
and snow through Sunday afternoon and evening. The low pressure
complex finally moves eastward during the day Monday, and could
also affect the Pribilof Islands with light rain and snow.

-AM

&&

.LONG TERM FORECAST (Days 4 through 7/Wednesday through Saturday)...

The Alaska upper level weather map opens with an energetic
pattern with several significant shortwaves passing across the
region. A closed low South of Kodiak Island drifts along the
Southern Gulf before exiting Southeastward for Friday. A moderate
amplitude but narrow ridge over the Central Aleutians and Bering
weakens and flattens as it moves into the Eastern North Pacific
through Saturday. A second low enters the Bering from the Russian
Far East, centers over the Central Aleutians and expands all the
way across Mainland Alaska into the Canadian Provinces in more
zonal flow by the weekend. A loose ECMWF / GFS / Canadian cluster
renders into an ensemble blend by Saturday, but supporting surface
instability throughout the period.

A moderate strength surface low South of Kodiak Island spreads a
shield of locally moderate rain from the Alaska Peninsula over
Kodiak Island and along the Southcentral Coast to the Canadian
Border through late Thursday before diminishing. Areas of snow are
expected inland, mostly over higher elevations. To the West, a
well developed North Pacific low and front pushes over the Western
Aleutians and Bering Wednesday. The system continues to spread
locally moderate rain over the Central Aleutians and Bering
Thursday before diminishing across the Eastern Bering and AKPEN
for Friday. Interior Mainland areas should remain under quiet
weather conditions.

- Kutz

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through Sunday
morning. Southeasterly Turnagain Arm winds may move over the
terminal Sunday afternoon.

&&


$$