Gale Warning 883, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
448 PM AKST Sat Dec 21 2024

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

A period of freezing rain was observed across Anchorage this
morning. Another round of rain and freezing rain is expected this
evening as low pressure centered south of Kodiak Island pushes
another front to the north Gulf coast. Rain has already overspread
much of the western Kenai Peninsula south of Soldotna as of 4 pm,
with the lifting front and accompanying shortwave aloft set to
bring at least a trace of (freezing) rain to Anchorage and
portions of the Matanuska Valley over the next several hours.
Despite some areas warming above and remaining above freezing,
surface temperatures remain in the upper 20s, which means that any
rain that falls will freeze to snow-free surfaces such as roads
and sidewalks. As a result, Winter Weather Advisories have been
issued for the western Kenai, Anchorage, and the Matanuska Valley.
These advisories last through Sunday evening, during which time
much of the area may remain dry. However, periods of rain/freezing
rain are expected with a series of shortwave troughs lifting
across Southcentral. Some locations, particularly those closer to
the mountains, where temperatures will be warmer (from the mid
30s up into the mid 40s), are expected to see accumulating
precipitation. Where surface temperatures remain below freezing,
up to a tenth of an inch of ice may accumulate.

Along the coast, expect periods of moderate to heavy rain with
each passing shortwave/front. The strongest features pass through
this evening through midnight and midday on Sunday. Ample warm
air will push snow levels as high as 3000 ft. Warm air moving into
the southern Copper River Basin will also lead to freezing rain
potential along the Richardson Highway as surface temperatures
remain below freezing to as low as about 10 degrees. The western
Copper River Basin near Eureka and Tahneta Pass will see enough
instability and moisture with Sunday's shortwave to receive up to
an inch of snowfall. On Monday, another shortwave lifting through
Southcentral will bring a surge of southerly winds, though
temperatures are not expected to appreciably warm with this. In
fact, temperatures begin to trend downward Monday night as colder
air wrapping in from around the decaying low pressure that remains
quasi-stationary in the vicinity of Kodiak Island and the Alaska
Peninsula begins to work in. By this point, chances of inland rain
and freezing rain will finally be coming to an end, at least
temporarily.

Quesada

&&

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

The predominant weather feature this afternoon is a low moving
south of Kodiak Island, poised to cross the AKPen into Eastern
Bering by Sunday morning. Gusty north to northeast winds have
continued across the AKPen to Kuskokwim Bay, with the strongest
gusts over open water. Several shortwaves rotating north around
this low will continue to bring bands of precipitation across
Southwest Alaska from this afternoon through Monday.

Precipitation type across Southwest remains the most difficult
aspect of the forecast as precipitation will have to pass through
a substantial warm, dry layer before reaching colder air at the
surface. Due to colder surface temperatures, Bethel may receive a
mix of snow and sleet, with a couple inches of snow possible for
the Pribilofs on Sunday. Precipitation for Dillingham and King
Salmon may remain as rain until Monday, then change to mixed rain
and snow through Tuesday. Winter Weather Advisories remain in
effect.

A second low approaches Bristol Bay from the Gulf between Sunday
and Monday, with more chances for freezing rain and rain/snow mix
across parts of the area through at least Monday morning. However,
both of these lows weaken and dissipate as a strong front
approaches the Aleutian Chain from the west Monday night. This
sends a band of easterly gale force winds and rain across much of
the Aleutian Chain by Tuesday afternoon.

&&

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

An elongated upper level trough extends from the Arctic through
the Eastern Bering into the North Pacific on Wednesday, with
several low centers rotating through the pattern. This trough will
slip over the Central Mainland into the Gulf of Alaska by the
weekend. A ridge over the Bering trailing the trough moves into
Southwest Alaska by Saturday. A second upper trough moves in from
Kamchatka over the Western Aleutians by Saturday. An upper ridge
over Southeast Alaska moves into the Canadian Provinces through
the end of the week. The ECMWF/GFS/Canadian models handle the the
strengths and tracks of the weather producers through the end of
the forecast period.

Most of the jet support rides across the North Pacific to the
South of the Aleutians and Alaska Peninsula. On the surface, a
series of lows and fronts will track over the Eastern Aleutians
and AKPEN over Kodiak Island into the Gulf before pivoting into
the North Gulf Coast. This will bring repeated rounds of locally
heavy rains to the Southcentral and AKPEN coastal zones and Kodiak
Island. Gusty Easterly winds spread over the Northern Gulf
Wednesday, and diminish Thursday. With cold air seeping across the
Interior from Canada, a band of mixed rain and snow or freezing
precipitation away from the coasts along the Northern edges of the
Precipitation areas, with snow mostly further inland. Gusty
Northeasterly winds just below gale force spread over the Central
and Eastern Bering and across the Aleutians and AKPEN through the
forecast period.

&&

.AVIATION...

PANC...VFR will largely prevail for ANC. Two fronts moving across
the Gulf will bring brisk easterly to southeasterly winds aloft,
with wind speeds of around 30 kt. This will lead to low level wind
shear through Sunday morning as surface remains will remain out of
the north. Guidance is trending towards a lower chance of
freezing rain and rain. If any rain or freezing rain occurs, it
will likely happen later this evening and overnight as a trough
moves through.

&&