012
FXAK68 PAFC 012350
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
350 PM AKDT Sat Jun 1 2024

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

A vertically stacked occluded low over the western Gulf of Alaska
will slowly retrograde to the south, reaching an area of the
western Gulf south of Kodiak Island by Sunday afternoon. Its
occluded front will remain draped over the northern gulf through
the weekend, producing steady rain and easterly gales across the
northern Gulf near the Barren Islands and the Stevenson Entrance
of Cook Inlet through Sunday morning as a series of upper-level
waves and vorticity lobes move along the front. Steady shower
activity will also continue along the immediate Southcentral
coast, especially across the higher terrain of the eastern and
southern portions of the Kenai Peninsula.

Farther inland across Southcentral, clouds and showers will be
increasing as an upper-level shortwave out ahead of the occluded
front moves from the northern panhandle of Alaska inland over the
Copper River Basin and Susitna Valley. This activity will keep
temperatures a few degrees cooler than what was observed Friday
across interior Southcentral.

Clearing skies and warming temperatures are expected Sunday as
the low over the western Gulf slides a bit farther south. This
will allow a ridge to push into the interior of the Southern
Mainland. For Kodiak Island, the low, coupled with an advancing
inverted trough, will allow showers and gusty winds to persist
into Monday. The inverted trough and associated easterly upper-
level wave will move into the eastern half of Southcentral with
another round of scattered showers likely from the Copper River
Basin to the Matanuska Valley Monday morning through Tuesday
afternoon.

&&

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

A broad upper low continues to linger over the Bering, causing
periods of light rain for the central and western Aleutians.
Meanwhile, continuing easterly waves from a low in the western
Gulf of Alaska are passing over Southwest and producing showers
for much of the Alaska Peninsula. If clearing takes place near the
foothills of the Kuskokwim Mountains, there is the potential for
a few isolated thunderstorms as instability increases this
evening.

Starting with the upper low in the Bering, weaker flow with the
system will result in limited impacts for the Bering. Most
precipitation will be light and winds will remain below small
craft criteria through tomorrow afternoon. Fog and misty
conditions that persisted over the Pribilof Islands this morning
are currently expected to reoccur tonight into early tomorrow
morning. Starting Sunday night, an Arctic trough begins to move
southward towards the northern Bering. Ahead of it, a surge of
below-normal cold air moves in and helps push the existing upper
low out of the Bering into the North Pacific. A shortwave low
south of the Aleutians passes by around this time and also helps
move and absorb the currently present upper low. The push of cold
air will also increase winds for much of the eastern Bering, with
most of those marine zones experiencing small craft force winds
through Tuesday afternoon. Some locations near Nunivak Island and
the Kuskokwim Delta, as well as south of the eastern Aleutians,
could see gale force winds late Monday into Tuesday. The low will
be wrapped in fairly dry air, so most locations over land will not
be significantly impacted by precipitation with this system. The
colder air over water could help produce enough instability for a
few light showers to occur on Monday and Tuesday. For places that
do get precipitation, temperatures could be cold enough for some
light snow to take place.

Moving on to the current unsettled weather in Southwest Alaska;
periods of easterly showers will continue to occur through at
least Monday night as the upper low in the Gulf of Alaska remains
close to the region. Before cold air from the Arctic low reaches
southwest, any daylight heating that takes place in the Kuskokwim
Valley and Bristol Bay areas could help support enough
instability for isolated thunderstorms tomorrow and Monday. The
current question mark in that portion of the forecast is that
since widespread cloud cover and rain showers are already present
over the region, will enough sunlight take place for thunderstorms
to develop in the afternoon hours of the forecast period. The
biggest potential for heavier rain will be tomorrow afternoon as a
band of rain forms over the Kuskokwim Valley and Bristol Bay and
moves southwest towards the eastern Aleutians tomorrow night. As
the Arctic low makes its way into the northern Bering Monday
night, a convergence boundary between it and the low in the Gulf
of Alaska forms just west of the Alaska Range. This area will
have enough energy and moisture to produce a precipitation band
through Tuesday afternoon before the Arctic low moves further
south and breaks up the boundary.

-BS

&&

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

The midweek upper level forecast opens with a pair of lows
stretching across the Southern portions of the state. The Eastern
Gulf low weakens and tracks through to the Southwest Gulf before
dissipating for Saturday. The Bering low center oscillates between
Bristol Bay and the Central Aleutians, and remains the most
persistent feature through the long term. Some additional energy
out of the Arctic through the Bering Strait helps pull the center
over the Central Aleutians. Jetstream support remains over the
North Pacific. A clustered GFS/ECMWF/CMC ensemble maintains the
best levels of confidence through the forecast period. The upper
level ridge over the Eastern Mainland supports surface thermal
troughs through the weekend.

Weak Southeasterly flow across Southcentral continues to pump
moisture inland to the Alaska Range. Most precipitation will be
showery, with best chances for convection in the Eastern Interior
and Copper River Basin. Almost direct onshore flow continues more
steady rainfall over Kodiak Island and the Alaska Peninsula. Gusty
Northerly surface winds are expected in the Eastern Bering
through Thursday. A number of surface features rotating over the
Bering brings the more active weather across the Pribilofs and
Aleutians.

- Kutz

&&
.AVIATION...

PANC...Gusty southeast winds out of the Turnagain Arm will
gradually abate late this evening into the overnight hours.
Afterwards and otherwise, VFR and light winds will prevail
throughout much of the TAF period.

&&


$$