Gale Warning 918, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
425 PM AKST Sat Dec 7 2024

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

A short wave is lifting northward through Cook Inlet this
afternoon and bringing some light rain to the far western Kenai
Peninsula, but most of the rain is remaining over the Inlet. By
the time this wave moves into the Susitna Valley this evening,
most of the precipitation show be snow and relegated mostly to the
Alaska Range.

Upper level flow will shift back to due south tomorrow and
increase temperatures again. Gale force winds, with a small core
of storm force winds for the Barren Islands, are expected along
the front with ample moisture with this system. Again, warm
southeasterly air looks to advect into Southcentral, so any
locations near freezing initially will quickly warm into the 30s
and 40s and snow levels again rising to 2,000 ft by Monday.
Turnagain Arm winds will also be on the increase, as well as winds
at higher elevations, including the Anchorage Hillside where
gusts to 60 mph are possible beginning Sunday night.

The front then weakens, slows, and stalls near Prince William
Sound on Monday. However, a strong upper-level wave moving north
into the Gulf will advect more moisture toward coastal
Southcentral as a second frontal boundary brings about another
round of gusty winds to the coastal waters, gaps, and higher
elevations of Southcentral Alaska. Upward of 2 to 3 inches of
rain could fall for coastal communities from Whittier to Kodiak
Sunday through Tuesday. Lesser amounts are expected farther east
toward Cordova. For locations in the lee of the coastal mountains,
a strong cross barrier flow and downsloping should limit any
chance for accumulating precipitation. However, there is a good
chance that precipitation falling in overnight hours in the lee
side of the mountains will be in the form of freezing rain with
surface temperatures dropping below freezing overnight and warm
air above freezing aloft.

-TM/EZ

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

The weak low that remains north of Nunivak Island continues to
dissipate as a strong low in the North Pacific continues to move
northward towards the Aleutians and Alaska Peninsula. Upper level
ridging building over the Alaska Peninsula and southwest Alaska
has allowed for quieter conditions today, but the break in the
weather will be brief as the ridge is quickly pushed out Sunday
morning into Sunday afternoon by the aforementioned North Pacific
low that will continue to head northwards into the Bering by
Sunday night. As of this afternoon, light rain and gale force
winds have already reached the central and eastern Aleutians.

The North Pacific low will send bands of precipitation across
Southwest Alaska, the Eastern Aleutians, and the Alaska Peninsula
through the weekend and into early next week. The Bering could see
a brief period of mixed rain/snow before warm air advection
occurs and transitions the precipitation fully to rain. Gale force
winds are expected accompany this low and will set up on the
southern coasts of the Aleutians and the Alaska Peninsula as well
as in Bristol Bay and the Southern Bering through Sunday.
Locations such as Cold Bay are expected to see a period of strong
winds with gusts to 50-60 mph possible early Sunday morning.

For Bristol Bay, the northeastern edge of the North Pacific low
tracks in early Sunday morning. Along with the incoming moisture,
increased temperatures will be moving in, with a brief period of
freezing rain possible but a quick transition to plain rain is
expected given the strong downsloping southeasterly winds quickly
warming the region to above freezing. The strength of the
southeasterly downsloping will limit the chances for precipitation
for much of the Bristol Bay region, particularly for the King
Salmon area. As the low lifts northward Sunday morning into
Monday, a favorable pressure gradient will increase the winds
through Kamishak Gap into portions of Bristol Bay with wind gusts
up to 40-50 mph.

For the Kuskokwim Delta and the Lower Kuskokwim Valley,
precipitation is expected to begin as snow Sunday morning, but the
possibility remains for a short period of snow mixed with
freezing rain before a quick transition to rain by Sunday evening.
Temperatures throughout Southwest Alaska are expected to rise
rapidly throughout the day Sunday, allowing for precipitation to
fall as all rain by Sunday night. Following the strong initial
wave of precipitation, the southeasterly wind is expected to keep
typically downsloped areas relatively dry by Sunday night.

-JH/CL

&&

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

At the start of the long-term forecast period, a storm force low
centered south of Kodiak Island early Wednesday morning will push
its front from the northern Gulf inland over Southcentral Alaska.
The front may briefly peak at storm force, though the bulk of the
strongest winds will be located south of the low center. Moderate
to heavy precipitation will accompany the front along the
Southcentral coast, primarily in the form of rain. Downsloping
will keep inland areas mostly dry, though a trace or few
hundredths of an inch of precipitation in the form of rain,
freezing rain, or snow cannot be ruled out, particularly as the
front lifts inland Wednesday/Wed night. The best chances for
precipitation at lower elevations will be some light snow in the
Copper Basin. The low weakens as it tracks into the Gulf
Wednesday and Thursday, with precipitation trending down along the
coast. However, there are divergent model solutions beyond this
point suggesting continued southerly flow sustaining rain/snow
shower activity along the coast into the weekend (GFS) or a
continued drying trend with a moisture tap directed more toward
Southeast Alaska (EC/GEM).

Along the Southwest coast, Alaska Peninsula, and in the eastern
Bering Sea, the weakening low's warm/occluded front lingers
through at least Thursday, producing primarily rain for marine
areas and snow inland. Colder air works in behind the weakening
Gulf low, tending temperatures downward for the latter half of the
week. Weak cold air advection will enhance northwesterly gap
winds across the Alaska Peninsula potentially to marginal gale-
force through Thursday night. The front along the Southwest coast
may shift inland Friday or Saturday, but this will be at odds with
the potential for a significant push of cold air dropping
southward across the Interior. Either solution will increase the
chance of light snow for inland areas of southern mainland
Alaska, despite different meteorological causes. Out west, low
pressure looks poised to arrive in the western Bering Sea late
Thursday into Friday, pushing into the central or even eastern
Bering Sea by Saturday. This looks to bring another surge of
warmer air and rain to the area through the weekend.

Quesada

&&.AVIATION...

PANC...VFR conditions and light northerly winds will prevail. Cannot
completely rule out a chance of freezing rain later this morning,
but confidence and coverage remain much too low to include in TAF
at this time.

&&