Gale Warning 661, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
459 PM AKDT Tue Oct 31 2023

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

Radar imagery and area observations show precipitation associated
with a weak trough moving through the Prince William Sound and into
the eastern Kenai Peninsula. Light rain and high-elevation snow is
expected through this evening but will gradually taper off through
the overnight hours. GOES water vapor imagery shows a large low
across the North Pacific that's gradually shifting northward,
partially in response to another low digging southeast across the
Aleutian Chain. Meanwhile, a NW-SE oriented ridge will continue to
bring generally quiet weather to portions of southcentral Alaska
north of the coast.

Temperatures should remain fairly mild, but will likely see more
cloud cover as low-level moisture gets trapped under the ridge. The
upper ridge will start to elongate and narrow as the Aleutian low
dives south. Models have come to an agreement that the North Pacific
low will shift up to just south of Kodiak Island and weaken as it
does so. This will bring increasing rain chances for the Gulf with
heavier rain favored along the western Gulf coast. Kodiak Island
will see rain showers increase in coverage tonight with rain likely
continuing for several days before the next break in precipitation.

MJB
&&

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

A North Pacific low south of the Alaska Peninsula and a low in the
western Bering will interact over the next several days to
produce gale force winds across the central Bering Sea and a
chance of freezing rain for parts of Southwest Alaska. While
conditions are relatively calm across the northern Bering and
Southwest Alaska today under the influence of high pressure
extending west from the mainland, this will begin to change
tonight. Winds increase to just below gale force along the Alaska
Peninsula as a front pushes up from the North Pacific, with rain
to accompany it. Northeasterly winds also begin to pick up across
Southwest Alaska in response to the increased pressure gradient as
the surface ridge axis is pushed north over the Interior. The
parent low in the North Pacific begins to interact with a decaying
low in the western Bering Sea, maintaining a strong front which
pushes into the central Bering. North to northeasterly gales
develop along this front as a result Wednesday night.

The eastern portion of this front, pushing north across Southwest
Alaska, will lead to increasing precipitation chances. However,
with weak upper-level forcing, precipitation is expected to be
light and intermittent. Northeasterly winds will lead to cooling
temperatures for Southwest Alaska through the end of the week,
which will bring temperatures below freezing near the surface
while east to southeasterly flow aloft brings in warmer air above
freezing. As a result, there is a moderate chance (around 50%) for
freezing rain in the Kuskokwim Delta Wednesday night and again on
Thursday night. With light precipitation, ice accumulations would
likely be trace to a few hundredths of an inch. There is a lower
chance for freezing rain in the Lower Kuskokwim Valley, where
precipitation will be even more sparse. Though these chances are
greatest on Thursday night. By Friday, a compact compact upper low
brings in much colder air to the northern Bering Sea, which will
intensify the front across the Kuskokwim Delta and transition
precipitation over to snow as the atmospheric column cools.

CQ
&&

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

Ensemble means work nearly all weather systems on the Alaska
weather map, with the exception of the ECMWF outlier as it applies
to the Gulf low. The Northern Bering low moves inland, sending
cooler temperatures and active weather into the Interior. A second
low out of the Russian Far East crosses the Bering and closes in
on Southwest Alaska through Tuesday. Widespread lower clouds and
mixed precipitation pushing inland over the Lower Yukon-Kuskokwim
Valleys, while winds approaching gale force move across the Bering
from Sunday on. In the East, a developing low brings large areas
of Easterly gale force winds from the Southeast Panhandle across
the Gulf through Tuesday. Gap winds to near gale force should
occur along the Alaska Peninsula and around Kodiak Island on the
backside of the low. Coastal areas will see more continuous
precipitation, becoming showery further inland across Southcentral
and Kodiak Island.

KZ
&&

.AVIATION...

PANC...VFR conditions and light northerly winds will persist
through the TAF period with ceilings remaining above 5,000 ft.

TM

&&