099
FXAK68 PAFC 301340
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
540 AM AKDT Thu May 30 2024

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

A weakening surface front will slow in its northward progression
as it reaches the Kenai Peninsula this morning. Southeasterly flow
ahead of the front will continue to advect moisture across the
Southcentral coast, resulting in persistent shower activity for
the eastern Kenai Peninsula, Prince William Sound, and the coastal
mountains. Farther north, a weak easterly wave traversing the
Alaska Range is producing an area of light rain over the northern
Susitna Valley this morning. This area of rain should taper off
after sunrise as the wave continues to move west.

Southeasterly gap winds have also persisted overnight, a result
of lift and lower pressure over the interior due to the the upper-
level wave over interior Alaska. These winds should diminish
after sunrise, but are expected to return beginning around noon
today as a second upper-level wave lifts north across Southcentral
through the day. This trough will also help to produce a few
isolated to scattered showers across interior Southcentral this
afternoon and evening. The best chance for shower activity will be
north and west of Willow and across the western half of the
Copper River Basin, where an isolated thunderstorm is also
possible. The gap winds will peak by early evening, with gusts
between 25 and 35 mph possible for West Anchorage and Palmer.

An upper-level shortwave and associated surface front will also
bring another round of widespread rain and gusty easterly winds to
Kodiak Island today. The gusty winds and rain will continue into
Friday as a strengthening area of low pressure enters the Gulf
from the north Pacific with its occluded front wrapping around the
low and extending back over the western Gulf.

This low will be the main feature for the end of the week as it
deepens into a gale-force low situated over the central Gulf.
Widespread rain and easterly gales will overspread the northern
half of the Gulf Friday morning, extending back into the western
Gulf by Friday afternoon. The low slowly moves to the northwest
for Saturday as it begins to weaken. By Saturday, there is some
uncertainty as to how far north and west the occluded front tracks
and whether an upper-level ridge extending across the western half
of Southcentral remains in place or begins to retreat to the west
as an easterly wave moves into the Copper River Basin from the
Yukon. If this easterly wave does help to break down the ridge,
scattered showers would return to interior Southcentral for the
weekend.

-TM

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Saturday night)...

A weak low centered north of Unalaska this morning maintains a
similarly weak front pushing onto the Southwest coast this
morning. Radar shows light rain showers slowly pushing north into
Bristol Bay, while much of the activity along the Kuskokwim Delta
coast is winding down. With high pressure situated off to the
east, southeasterly winds continue out of Kamishak Gap. These
winds will increase somewhat during the day, similar to yesterday,
as the boundary layer deepens and stronger winds aloft mix down to
the surface. Also during the day today, increased moisture from
the front spreading northward will allow isolated to scattered
showers to develop across much of Southwest Alaska and track
northwestward into the evening hours. Southeasterly winds begin to
relax this evening as a strengthening low enters the Gulf of
Alaska, weakening the pressure gradient across the Alaska Range.
While the low in the eastern Bering dissipates this evening, the
Gulf low extends a warm front along the Southwest coast,
reinforcing the weakening feature and bringing another round of
light rain Thursday night.

The front quickly weakens for Friday, but the Gulf low`s effects
in Southwest Alaska do not end there. The low draws warm air from
Interior Alaska southwestward, leading to an increasing
temperature trend and a building ridge for this weekend.
Conditions look fairly quiet initially on Friday, with less shower
coverage than expected today. However, by this weekend, increasing
temperatures and weak shortwaves rotating across Southwest Alaska
may bring enough instability to support a few thunderstorms.

- Quesada

.SHORT TERM FORECAST BERING SEA AND ALEUTIAN ISLANDS (Days 1
through 3: Today through Saturday night)...

A 965 mb low off Kamchatka extends a front across the western
Aleutians this morning, bringing moderate rain and gusty
southeasterly winds to gale force. The low and front track
eastward, weakening below gale force as the front moves into the
central Aleutians later today. Behind the front, a second round of
rain showers can be expected, along with gusty southerly winds.
The front reaches the Pribilof Islands and the eastern Aleutians
for Friday. The low weakens by Saturday into an open trough.
Despite lingering troughiness across much of the Bering Sea, very
little precipitation is expected. Winds begin to intensify out of
the north by Sunday in response to the extratropical remnants of
Typhoon Ewiniar passing south of the Aleutian Chain, but remain
below gale force. Some uncertainty in the track of this low lends
decreased confidence to whether the western and central Aleutians
see any precipitation from its associated front. Stay tuned for
future updates as the forecast is refined.

- Quesada

&&


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

Some changes coming to the Alaska Weather Map through the
forecast period. The upper level low center in the Gulf of Alaska
weakens and becomes absorbed by a second low center sliding in
from the Bering by Tuesday. The elongated zonal trough aloft
across the Western Bering to the Gulf shortens with the
introduction of an Arctic low sliding Southward along the West
Coast, stalling out in the Eastern Bering by Tuesday. A weak upper
level ridge builds over the Russian Far East in the Western void
through midweek. The upper level ridge over the Central and
Northern Mainland also weakens slightly, but maintains enough
substance for thermal trough formation over the Eastern and
Central Interior.

Continued Easterly to Southeasterly airflow over the Southcentral
areas spreads increased moisture as far North as the Alaska
Range, and brings showers with each Easterly wave. Potentially
larger amounts of rain over the Copper River Basin associated with
more convective events are expected. Transient lows, fronts and
troughs spread their precipitation over the Aleutians and Bering,
and into Southwest Alaska, and the AKPEN and Kodiak Island. Some
energy from the Arctic low should generate showers along many West
Coast areas.


-Kutz

&&
.AVIATION...

PANC...VFR conditions will persist. Gusty winds early this morning
will diminish after sunrise, but are expected to pick back up out
of the south from Turnagain Arm by early this afternoon. These
winds will likely persist through this evening before diminishing
again tonight.



&&


$$