Gale Warning 689, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
551 AM AKST Sun Nov 12 2023

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

After some sunshine today (once it finally rises of course),
clouds will rapidly move in from the west as a front approaches
Southcentral Alaska. This front will be fairly fast moving but
will bring in widespread snowfall across Southcentral from tonight
through Monday. Heaviest snowfall will be in Anchorage and the
Mat-Su. In these areas there will likely be some snowfall rates at
or a little over an inch and hour for a few hours late tonight
into Monday morning. This system is a very different structure
than the ones from last week so it is unlikely that the snow will
linger around any of these areas and should shut off by late
Monday morning as it heads into the Copper River Basin.

The biggest forecast challenge for this system, is determining
whether there will be a periods of southeast winds over Anchorage
and the Matanuska Valley overnight or if they stay northerly at
the surface. The GFS model wants to keep them northerly all the
way down Cook Inlet the entire period while the NAM and the suite
of Hi-resolution models are showing the southeast wind
development. These winds will not be terrible strong, but will
have an impact on snow amounts in these areas. These southeasterly
winds would have the effect of having south and west Anchorage
with the highest amounts with northeast Anchorage and especially
Eagle River with lesser amounts of snow. For the Matanuska Valley,
it will lessen the amount of snow in Palmer and push the heavier
snowfall to Wasilla and Knik-Goose Bay road.

Snowfall will also occur over the Kenai Peninsula with the snow
likely switching over to rain around Kachemak Bay late tonight.
This is also dependent on the wind direction turning to the south
to southeast for much of the night. As with the case in Upper Cook
Inlet, the GFS model wants to keep winds northerly and
temperatures colder than the NAM and hi-resolution models. The
more likely situation is for the southeasterly flow and rain
around Kachemak Bay, though it likely will not make it much
further north than that.

&&

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

The short term forecast remains largely on track with minimal
changes made. A high amplitude ridge builds from the Bering into
Mainland Alaska and is followed by an expansive upper trough and
embedded low. The low will continue tracking all the way up to the
Russian Arctic today. Its attendant surface front draped across
the central Bering and Aleutians this morning is bringing
widespread rain and gale force southerly winds with it. The front
will push across Southwest Alaska today. Conditions will initially
be cold enough for snow as precipitation first arrives, but much
warmer air aloft will lead to a quick transition to rain for the
Kuskokwim Delta and coastal areas of Bristol Bay. A brief period
of light freezing rain is possible for these regions this morning
into the early afternoon during the transition from snow to rain.
Any ice accumulations are most likely to be trace to a tenth of an
inch. Precipitation will spread across interior Bristol Bay and
Lower Kuskokwim Valley later today and will most likely remain
snow, although a brief period of mixed precipitation is possible
near Aniak early this afternoon. By tonight, much colder air
behind the front is expected to turn any remaining precipitation
to snow. The combination of cold air advection and short-waves
rapidly tracking eastward across the Bering Sea will bring a
showery regime to the Bering, Pribilof Islands, and into Southwest
Alaska for Monday.

Another storm system will track from the Pacific to the Aleutian
chain Monday, with gale to storm force winds likely over the
coastal waters. Much warmer air aloft will accompany this low,
ensuring balmy surface temperatures and a precipitation type of
all rain. The system's low center is currently advertised to
elongate as it tracks over the Bering for Tuesday and Wednesday.
Its front will lift along the Aleutians on Tuesday and reach
Southwest Alaska by Tuesday evening, and then the low itself will
follow and track into Southwest on Wednesday. This system is
expected to bring rain and widespread gales (possibly storm force
winds) to the Bering and Aleutians Tuesday and Wednesday, and
another round of snow to Southwest Alaska.

AF

&&

.LONG TERM FORECAST (Days 4 through 7)...

A very progressive weather pattern will continue into and through
the extended range forecast period with multiple strong
shortwaves riding over a strong but broad ridge over the Northern
Pacific. Measures of predictability are good through Friday of
next week and very reasonable clustering of ensemble solutions.
The broad longwave ridge moves across the Southern Mainland
through Thursday. A well developed shortwave trough approaches
Bristol Bay for Wednesday and moves across the Gulf of Alaska
through Thursday. Gale force winds and locally heavy precipitation
will occur from Western Alaska and the Alaska Peninsula. Will
continue to monitor the potential for high surf, coastal flooding
and strong winds from Nunivak Island southward to Bristol Bay.
Gales will continue around Kodiak Island and over the Southern end
of the Kenai Peninsula through Wednesday. Areas of heavy snow for
the Alaska Range and parts of the Kuskokwim Valley. Widespread
precipitation is expected from the Eastern Kenai Peninsula across
the Southcentral Coast to the Canadian border through Thursday.
Expect below normal temperatures to make a return to mainland
Alaska including Southcentral beginning Friday of next week.

CC

&&

.AVIATION...

PANC...A storm is expected to arrive tonight with heavy snow
through Monday morning. Ceilings are expected to drop below MVFR
around midnight and continue to lower further into IFR at times Monday
morning with heavier snowfall. Snowfall rates of an inch per hour
are likely during the heaviest period of snow, between 12Z and
18Z Monday morning. Winds will increase from the southeast after
midnight Monday morning with a brief gust up to 25 to 30 mph
possible. Winds will quickly shift to northerly late in the
morning and become light and variable for the afternoon. Snow
should end by the early afternoon Monday.

rux

&&

SPECIAL WEATHER STATEMENT
National Weather Service ANCHORAGE AK
422 AM AKST Sun Nov 12 2023

AKZ155-161-130300-
Kuskokwim Delta-Bristol Bay-
Including the cities of Bethel, Nunivak Island, King Salmon,
Dillingham, Naknek, and Pilot Point
422 AM AKST Sun Nov 12 2023

...FRONTAL SYSTEM TO BRING TRANSITIONS BETWEEN SNOW, RAIN, AND
FREEZING RAIN TODAY...

A front will begin to push inland across Southwest Alaska this
morning bringing with it warmer air. Initial snow is forecast to
transition to a rain/freezing rain mix as a result of the warmer
air pushing atop at or sub-freezing surface temperatures. While
locations from Bethel to Dillingham, and even New Stuyahok, may
experience a brief period of light freezing rain in the morning,
the temperature warm-up to above freezing should be fast enough to
limit accumulations to a trace or a few hundredths of an inch at
best. Much colder temperatures remain forecast to move back into
Southwest behind the front, bringing any mixed precipitation back
to snow by tonight.