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000
FXAK68 PAFC 170035
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
435 PM AKDT Tue Apr 16 2024

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

An upper level ridge centered over the ALCAN border continues to
slide eastward, allowing a trough over the central Bering to
deepen and stall, strengthening a North Pacific low south of
Kodiak and the western Gulf. This new low will remain in place for
several days. While most of Southcentral will experience a slight
warming trend, this system is expected to bring moderate to heavy
rain to Kodiak Island and portions of the eastern Kenai Peninsula
lasting through Friday. In addition, gale to storm-force winds
winds will develop across the western Gulf and Barren Islands
tonight through Wednesday.

Several shortwave troughs on the southern periphery of the
longwave trough will lift north towards Kodiak Island and into
Southcentral. The heaviest period of precipitation is expected on
Wednesday around noon. Temperatures may initially be cold enough
at lower elevations to begin as a rain/snow mix on Kodiak, but
should quickly warm and change over to all rain by Wednesday afternoon.
Moderate to heavy rainfall looks to persist into Thursday, but
could see showery conditions linger through Friday. Models remain
fairly consistent with rainfall amounts of about 4 to 6 inches
along the southeast side of Kodiak and up to several inches for
lower elevations along for coastal areas for southeast Kenai
Peninsula. Elsewhere precipitation is expected to be light to dry.
No measurable precipitation expected for the rest of the week
from Soldotna to the Mat-Su Valley.

&&

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

A decaying front draped over the Y-K Delta this afternoon
continues to be the focus for areas of mixed rain and snow from
Aniak to Toksook bay. This front will continue to weaken as it
remains nearly stationary overnight, replaced by an inverted
trough extending northward from a North Pacific low advancing
toward the Alaska Peninsula. Moisture associated with the low will
stream northwestward, along broad southeasterly winds aloft. The
moisture will concentrate along the trough axis, wringing out over
the Kuskokwim Delta overnight and into Wednesday morning. Winds
near the surface will turn a bit more northerly, allowing enough
colder air to advect at lower levels for the precipitation to fall
mainly in the form of snow, especially from Bethel west. The
heaviest snow is expected over the Kuskokwim coast, right along
the trough axis. 5 to 10 inches of snow is possible before warmer
air works back in Wednesday afternoon, allowing for a mix with
rain. Farther south across Bristol Bay, enough warmer air and a
southeasterly wind should allow for precipitation to fall mainly
in the form of rain.

As the low lifts north tonight, the pressure gradient between it
and a stout ridge anchored over the Alaska Panhandle will tighten.
The result will be an increase in winds through Kamishak Gap and
across interior Bristol Bay, where wind gusts could peak around 70
mph by Wednesday morning. Farther along the coast, winds will not
be as strong, but gusts of 45 to 55 mph are not out of the
question.

For the Bering and Aleutians, precipitation from the trough will
likely extend southwest from the Kuskokwim Delta to the eastern
Aleutians. Colder air on the west side of the trough will allow
temperatures to drop to around freezing overnight. A second
shortwave diving south from east of the Russian coast will advect
colder air in aloft for Wednesday just as the moisture axis
pivots toward the Aleutians. The result looks to be moisture
moving into an increasingly cold and unstable airmass, with the
potential for heavy snow over the eastern Aleutians. Places like
Unalaska / Dutch Harbor could see several inches of snow, the
current thought is 6 to 12 inches, along with northerly wind gusts
of 50 to 60 mph for Wednesday. The moisture axis looks to stay
just to the east of the Pribilofs; however, if there is any
westward jog in this system, snow may accompany the gusty winds
across Saint Paul and Saint George Islands as well.

The unsettled conditions will continue into Thursday and Friday;
however, winds will slowly diminish from their peak Wednesday and
precipitation will become more showery and not as widespread.

-TM

&&




.LONG TERM FORECAST (Days 4 through 7: Saturday through Tuesday)...

A moderately strong area of high pressure over the the Northern
Canadian Provinces extends a ridge across Mainland Alaska through
the forecast period. The strength of the ridge weakens, but holds
its orientation across Interior Alaska. In the Gulf, a persistent
closed low remains nearly stationary linking up with a second low
in the Bering. The Gulf low will also weaken through the weekend
as the Bering low is expected to drift over the Mainland ridge
into the Arctic through Tuesday. A North Pacific low moves over
the Aleutians for the beginning of next week.

A front connecting the Gulf low with the Bering low provides the
stream for an extended period of wet weather from the Southern
Kenai Peninsula across Kodiak Island into the Alaska Peninsula.
Widespread rainfall will continue with locally heavier periods of
rain will bring several additional inches through the weekend. A
trough swinging around the low spreads rain over much of the
Southcentral coast. Southwestern Alaska may see mixed rain and
snow to the West of the vertically stacked trough, with snow
expected further North along the Western Coast.

-Kutz

$$

.AVIATION...

PANC...VFR conditions are expected to prevail through the period.
Turnagain Arm winds should lessen later this evening as the
stronger Turnagain Arm winds will shift down-inlet with light
northerly winds over the terminal. Tuesday should see these
Turnagain Arm winds remain mostly down-Inlet, but there is a
chance for a period of southerly winds again in the late
afternoon due to daytime heating.

&&


$$