Gale Warning 824, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
536 AM AKST Thu Nov 14 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
Thursday through Saturday evening)...

A pattern change is on tap for Southcentral as the upper-level
ridge overhead this morning quickly slides east as the next storm
system moves toward the region from the west. In the meantime,
conditions are generally rather tranquil this morning over most
locations, with mainly clear skies and very cold temperatures. An
area of fog remains over Knik Arm, extending across Anchorage this
morning. There is also an area of fog along the Glenn Highway west
of Glennallen. Gusty northerly gap winds are also continuing this
morning for Resurrection Bay, Passage Canal, Valdez Narrows, and
Thompson Pass. These winds will quickly diminish as the ridge
moves east.

A frontal system will move over Kodiak Island this morning, with
rain and gusty easterly winds. These wind down for Kodiak later
today as the front begins to move over the Kenai Peninsula. As it
does, a triple-point low will spin up somewhere between Seward
and Chenega. This organization will likely maintain the system as
it pushes up into the Peninsula and Prince William Sound. As the
system overspreads Southcentral Thursday afternoon, precipitation
will fill in the region from Cook Inlet and the Mat-Su valleys
east into Prince William Sound. With plenty of cold air in place
ahead of the front, precipitation will start as snow for most of
Southcentral, with warmer air moving in for coastal locations, a
shift from all snow to a rain/snow mix is possible. With those
exceptions, Southcentral will see generally snowy weather
overspread the region, with the highest accumulations expected in
the Prince William Sound region. The initial surge of moisture
will likely allow for a quick shot of light snowfall for Anchorage
late Thursday afternoon before the winds orientate in a more
downslope favored pattern. For Portage Valley and Turnagain Pass,
the combination of snow and wind, at least initially, may produce
a period of blowing snow. Several inches of snow is also possible
for Valdez and Thompson Pass with this system. Snow and blowing
snow is also possible for coastal Western Kenai Peninsula. The
extent of any blowing snow will be dependent on where the band of
steady snow sets up. Guidance is still struggling with whether the
band sits over the Sterling Highway or farther west over the
inlet itself. Multiple Winter Weather Advisories and Special
Weather Statements are in effect for the Kenai Peninsula and
Valdez area.

Given that the system organizes and pulls into a low pressure
system, precipitation is expected to persist into the early
weekend. By Friday morning, the low is expected to shift the wind
field and allow for a band of snowfall to re-establish from Palmer
to Kenai including Anchorage. This band on the backside of the
low is currently expected to lack a substantial moisture content
but a favorable persistence. This could indicate a potentially
long-duration very light snow event for Anchorage and the
surrounding area from Friday morning into Saturday.

-CL/TM

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, AND THE BERING
SEA/ALEUTIANS (TODAY THROUGH SUNDAY AFTERNOON)...

A mid-November storm will continue to bring snow, strong winds
high surf and rain to Southwest Alaska into Friday morning.

* Kuskokwim Delta: Blizzard Warning for parts of Kuskokwim Delta
  north and west of the Kuskokwim River, including Nunivak Island.

* Lower Kuskokwim Valley: Winter Weather Advisory for 6-10 inches
  of snow.

* Bristol Bay: High Surf Advisory for Togiak Bay coastline.

* Bristol Bay: Special Weather Statement for Greater Bristol Bay
  due to gusty winds, blowing snow, and snow transitioning to
  rain.

Through Friday evening: The arrival of this morning's front
and its precipitation and winds resulted in lower ceiling
heights, visibility reductions falling to 1/4 mile and blowing
snow. Wind gusts ranging from 30 mph to 40 mph inland and as high
as 60 mph along the SW coastline accompanied with reports of
freezing rain, rain and snow through 4:00am today. Current
guidance shows the low behind the front will move in a more
northeasterly direction resulting in increased confidence of
blizzard conditions to the north and west of the Kuskokwim River.
This track will bring warmer air south of there from the AK Pen
northward to Dillingham. Therefore, confidence remains moderate
that this morning's wet snowfall changing to a rain/snow mix this
afternoon and then to all rain this evening from south to north.
Wind gusts during the changeover will increase too with the
strongest winds this afternoon into the late evening hours. Though
these onshore winds from Clarks Point to Egegik could switch
briefly to a more southerly direction early Friday morning, the
main onshore wind direction will be southwesterly.

Saturday and Sunday: Northerly to northwesterly winds will
continue to bring cooler air into the Aleutians, SW Alaska and AK
Pen as waves of weak disturbances move through the Bering this
weekend. Gap winds in the region are likely to increase tomorrow
too.  Temperatures continue to trend cooler resulting in a
decrease of daytime highs and overnight lows across the region.

-DJ

&&

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

Sunday, a low over the northern Gulf of Alaska weakens and moves
southeast, reducing the persistent shortwave precipitation over
the Kenai Peninsula. As it departs, gale force wind will be pulled
southeast across the Alaska Peninsula and out of Cook Inlet. This
drier northerly flow will cause clearing skies and colder
conditions. Single digit temperatures are expected for most of
Southcentral Sunday night through Wednesday, with below zero
temperatures across the Copper River Basin, where lows dip into
the negative teens Tuesday and Wednesday.

To the west, a shortwave low over the Aleutian Chain moves
eastward on Sunday, strengthening to push a front of gale force
winds into the southern Gulf by Tuesday morning. In its wake, a
ridge builds across the Bering Sea and Southwest Monday and
Tuesday, before a front of a northern Kamchatka low pushes across
the Aleutian Chain and Bering Sea Tuesday to Wednesday.

&&.AVIATION...

PANC...LIFR conditions are expected to persist through the
morning hours as fog remains in the area. Conditions should
improve with the northerly wind picking up, helping to clear out
the fog by late morning. As a brief period of snow moves in this
evening, visibilities and ceilings may drop to MVFR levels.
Although VFR conditions are expected to prevail Thursday night
into Friday morning, low level wind shear will be a concern
overnight with strong southeasterly wind aloft. MVFR/IFR
conditions are expected to return by the end of the TAF package
with another round of light snow.

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
345 PM AKST Thu Nov 14 2024

AKZ126-151500-
Western Prince William Sound-
Including the cities of Whittier, Seward, and Moose Pass
345 PM AKST Thu Nov 14 2024

...AREAS OF SNOW AND BLOWING SNOW FOR TURNAGAIN PASS AND WHITTIER
THIS AFTERNOON THROUGH FRIDAY MORNING...

Snow and gusty easterly winds for Whittier and Turnagain Pass
have begun increasing, and will continue to grow into this evening.
The combination of snow and winds gusting to 40 mph for Whittier
and 30 mph for Turnagain Pass will result in areas of blowing and
drifting snow. 3 to 6 inches of snow is possible through early
Friday morning.

For Whittier, temperatures will climb quickly to near freezing.
Warming temperatures may limit the extent of blowing snow. There
is still some uncertainty as to how quickly temperatures will
climb above freezing. Any delay in warming will allow for
additional snow accumulations along with blowing and drifting
snow. Snow is expected to mix with or change to rain after
midnight.

For Turnagain Pass, temperatures are expected to stay at or below
freezing, allowing for precipitation to fall as all snow. Light
snow will continue through Friday; however, winds will diminish by
early Friday morning.