Gale Warning 922, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 PM AKST Sun Dec 8 2024

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

Temperatures below freezing with northerly winds this morning for
the western Kenai Peninsula, Anchorage, and the Matanuska Valley
slowly eroded throughout the day as southeastern winds interacting
with terrain filtered warmer air westward. Portions of Anchorage
ranged from 28 degrees at the Anchorage International to 46
degrees near south Anchorage. The prevailing south and easterly
flow will continue bring about warming temperatures, especially
for coastal locations that will see an increase in winds off the
waters of the Gulf.

Warmer air flowing over the cooler surface in some spots allowed
for brief, light freezing rain in Soldotna and Kenai, then
Anchorage this morning. Light, freezing rain has been reported
this evening from Big Lake north through Willow. These are
expected to be brief as dry air within a region of downsloping
spreads northward. There is a good chance that precipitation
falling during the overnight hours on the lee side of the
mountains will be in the form of freezing rain with surface
temperatures dropping below freezing overnight and warm air still
above freezing aloft. Kodiak received ample rainfall (over 2
inches) since this morning. Rain rates have gotten lighter, but
additional rain is expected to increase again overnight into
Monday for Kodiak. An additional 2 to 5 inches of rain could fall
for coastal communities from Whittier to Kodiak through Tuesday.
Lesser amounts are expected farther east toward Cordova.

Widespread 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 with snow levels
again rising to 2,000 ft or higher by Monday. Turnagain Arm winds
will also be on the increase, as well as winds at higher
elevations, including the Anchorage Hillside where gusts 55 to 70
mph are possible overnight and Monday. Strong wind gusts
approaching 45 to 60 mph area also possible for Whittier and
Portage.

The front weakens, slows, and stalls near Prince William Sound
early Monday morning. However, a strong upper-level wave moving
north into the Gulf will advect more moisture toward coastal
Southcentral as a surface low spins up along the stalled frontal
boundary and drives north toward Prince William Sound. This low
will drive the front to the coast with a storm-force barrier jet
developing from Cordova into western Prince William Sound. Any
slight lull in the gusty winds from the initial frontal push late
Sunday into early Monday will be short-lived as the low and front
continue to push inland by Monday afternoon with a second peak of
strong winds likely from Cordova to Whittier, Portage and
Turnagain Arm.

-TM/Rux

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

The North Pacific low pressure system will continue northward
into the southeastern Bering Sea this evening, continuing the
warming trend and rainy weather for the Alaska Peninsula and
Southwest Alaska. As of this afternoon, widespread and rapid
warming has allowed temperatures to rise above freezing across
Southwest Alaska, with the only freezing temperatures hanging on
in parts of the Lower Kuskokwim Valley. As such, periods of
freezing rain observed throughout this morning and early afternoon
in Bristol Bay, the Kuskokwim Delta, and most of the Lower
Kuskokwim Valley has concluded with precipitation fully
transitioning to rain or tapering off. Areas still experiencing
freezing rain in the Lower Kuskokwim Valley are expected to
continue to warm throughout this evening promoting the transition
to plain rain.

The bulk of the precipitation associated with this system
continues to head north out of the area as winds continue to turn
southeasterly, promoting a strong downsloping signature on radar
for much of Bristol Bay and the Kuskokwim Delta regions. A
prolonged period of rain showers and snow showers at elevation
remains possible throughout Southwest Alaska for the next several
days as the current low continues to head north in the Bering
through Monday and a new system approaches the Aleutians from the
North Pacific by Tuesday morning. Gale force winds are expected to
continue in the southeastern Bering through Monday morning with
gusty winds for Bristol Bay through Kamishak Gap continuing into
Monday afternoon.

As another North Pacific low approaches the Aleutians by Tuesday
morning, the prolonged period of southeasterly winds and warm
pattern is expected to continue into midweek, although details
regarding this next system remain uncertain given the substantial
model spread in the track of the low. Models continue to trend
towards a northerly track as the upper level ridge over eastern
Alaska and Western Canada steers the low towards the Alaska
Peninsula and southeastern Bering. This system is expected to
bring another swath of gale force winds south of the Alaska
Peninsula and in the southeastern Bering as well as gusty winds
through Kamishak Gap once again for Bristol Bay. Widespread rain
showers across Southwest Alaska will be possible through Wednesday
morning, with the greatest rainfall amounts expected for the
Alaska Peninsula and areas most susceptible to southeasterly
upslope flow in southwest Alaska. Temperatures are expected to
remain warm enough to keep precipitation as all rain through
Wednesday morning, except for snow showers at high elevations.

-JH

&&

.LONG TERM FORECAST (Days 4 through 7: Thursday through
Sunday)...

On Thursday, a negatively-tilted trough extends east over
Southwest Alaska and into the Gulf from a broad upper low over
the far western Bering Sea. Enhanced lift provided by the trough
and weak southerly flow will support light rain showers along the
north Gulf coast, with potential for light snowfall for inland
portions of southern mainland Alaska. The trough cuts off into a
weak upper low that shifts into the eastern Gulf for Friday,
focusing the best potential for precipitation in eastern Prince
William Sound and the Copper River Basin. Meanwhile, cold air from
the Interior filters south, trending temperatures down for the
latter half of the week into the weekend.

Out west, a longwave trough remains anchored near Kamchatka. This
brings a strong gale to storm force low into the far western
Bering for Thursday and Friday. Its front pushes to the Southwest
coast by Friday, but there is significant uncertainty in
precipitation type, with temperatures marginal either rain or snow
are possible depending on solution. A ridge builds off to the
east into the Gulf, trending precipitation chances down over
Southcentral Alaska for the weekend. There are, however,
indications in the model guidance that the front along the
Southwest coast sweeps inland and brings another surge of moisture
and precipitation into the southern mainland by Sunday, but there
is significant spread in the areas that are most favored, with
potential for both coastal and inland precipitation. Late in the
weekend, a large storm or hurricane force low looks to approach
the Aleutians, bringing moderate rainfall to the islands and the
southern Bering.

Quesada

&&.AVIATION...

PANC...A complex weather situation will persist around the
airport into Monday. With winds at the terminal expected to remain
mainly northwesterly through the night, temperatures will remain
mild, but mainly below freezing. This was the cause of the
freezing rain today with southeast winds aloft bringing in warmer
air over the below zero surface temperatures in the northwesterly
winds. This combination of northwest surface winds abruptly
becoming southeasterly around 500 to 1000 ft will keep winds shear
in the area through Monday morning. By early Monday afternoon
strong southeasterly winds should push over the airport and both
end the wind shear while turning any precipitation at that point
to all rain. These winds should persist through much of Monday
night and then diminish.

&&