783
FXAK68 PAFC 221350
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
450 AM AKST Wed Jan 22 2025

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3: Today
through Friday Night)...

Mild and unsettled weather will continue for Southcentral Alaska
through the end of the week. For today, scattered to numerous
showers are expected across the much of the forecast area, save for
the central Copper River Basin through Mentasta Pass, as an upper-
level trough lifts northeastward across the state. Relatively warm
low-level air in place will lead to rain or a rain/snow mix,
particularly from Anchorage south through the Kenai Peninsula at low
elevations. Not everybody today will receive precipitation, owing to
the loosely organized nature of the showers. The areas most likely
to see accumulating precipitation today will be the locations that
benefit from southerly upsloping flow such as: 1) Homer Bluffs, 2)
Northern Susitna Valley, 3) Hatcher Pass area of the Talkeetnas, and
4) the upwind side of the Central Chugach that includes Valdez,
Thompson Pass, and Cordova. The highest snow totals across the road
system are expected to be in the northern Susitna Valley,
particularly along the Parks Highway north of Trapper Creek to Broad
Pass, where 4 to 8 inches of snowfall is anticipated by the end of
the day.

After a brief lull in precipitation this evening in wake of the
first trough, a second and more vigorous upper-level trough will
quickly swing into Southcentral AK tonight into early tomorrow.
Precipitation will be a bit more widespread than Wednesday`s system
owing to the stronger nature of the trough. Many of the same areas
that received accumulating snowfall Wednesday will see accumulating
snowfall again Thursday, but this time a bit more. One caveat is
that modest warm air advection will warm an already mild boundary
layer. Rain may then mix in with snow all the way north into the
central and possibly northern Susitna Valley at times. Additionally,
the southern Kenai Peninsula including the Homer Bluffs should
also see a changeover to mostly rain as Thursday progresses.
Precipitation will taper off most everywhere Thursday night into
early Friday with snow potentially lingering a bit longer in the
northern Susitna Valley.

Southwest flow across much of mainland Alaska into the Gulf of
Alaska will deepen and intensify Thursday into Friday in response to
the pressure gradient intensifying between an amplifying ridge
across the North Pacific and deep low pressure in the Bering Sea.
Models are in good agreement with precipitation spreading across
Southcentral AK Friday as a robust atmospheric river pulls northward
underneath the favorable right-entrance region of a 140+ kt
supergeostrophic jet streak. Anomalously deep warm air will
result in snow levels rising significantly across all but the
Copper River Basin. Latest NBM guidance shows snow levels
approaching 4000ft ASL by Friday afternoon. While these values may
be overdone, this suggests a very warm, moist airmass being
pointed towards Southcentral Alaska. Snow levels won`t be quite
that high north of the southern Kenai, but most anywhere along the
road system (minus Copper River Basin potentially) will likely
see snow transitioning to rain Friday into Saturday. Stay tuned to
the forecast as this marks the start of a very active weather
pattern across Southcentral AK, with strong signals pointing to a
significant pattern change after this event.

-Brown

&&


.SHORT TERM FORECAST SOUTHWEST ALASKA AND THE BERING
SEA/ALEUTIANS (Today through Saturday morning)...

Currently, a shortwave trough continues to push inland of the
Kuskokwim Delta and Bristol Bay this morning which is helping rain
and rain/snow mix to persist across those areas. This activity
continues eastward to the Lower Kuskokwim Valley and interior
Bristol Bay through today.

The next systems to watch are currently a Kamchatka front and a
low over the Western Aleutians this morning. These systems will
interact with each other as they push east across the Aleutian
Chain and to the Pribilof Islands today. Mostly gale-force winds
are expected across the North Pacific and Bering Sea with these
systems. However, a corridor of sustained storm-force winds are
possible in the North Pacific marine zones just south of the
Aleutian Chain along the southern flank of the storm. Mostly rain
is expected with this system. The Pribilof Islands could start out
as a brief period of rain/snow mix before going over to rain this
afternoon. The front reaches mainland Southwest Alaska by this
evening bringing with it more gusty southerly winds to the coast
as well as rain and rain/snow mix. This activity pushes inland to
the Lower Kuskokwim Valley and interior Bristol Bay by Thursday
morning.

A more significant and impactful storm system organizes Wednesday
evening in the North Pacific. The front quickly advances to the
Aleutian Chain early Thursday morning bringing strong gusty
southerly winds to the Eastern Aleutians and Southern Alaska
Peninsula (AKPEN) through Thursday. There is moderate to high
confidence that storm-force winds with hurricane-force wind gusts
will accompany this system with the core of the strongest winds
passing over the Eastern Aleutians Thursday. Therefore, a High
Wind Warning has been issued for the Eastern Aleutians that goes
into effect 4 AM AKST Thursday morning through 10 PM AKST Thursday
night. Nikolski and Akutan have the best chance at seeing
southerly wind gusts up to 80 mph. Unalaska/Dutch Harbor look to
be protected from the strongest winds due to the southerly
direction. This area can still see gusts between 40 to 60 mph
though. There is lower confidence if hurricane-force wind gusts
make it across the southern AKPEN and into Cold Bay Thursday
afternoon into Thursday night. In addition to the strong winds,
moderate to heavy rain will also accompany this system.

This system quickly crosses into the Bering from the North Pacific
Thursday afternoon as it elongates. The system then tracks from
the vicinity of the Pribilof Islands Thursday afternoon to just
east of Saint Lawrence Island by early Friday morning. This track,
along with the strong pressure gradient between the storm itself
and North Pacific high pressure near the Alaska Panhandle will set
the stage for sustained southerly flow into Kuskokwim Bay. The
Coastal Flood Watch remains out for the Kuskokwim Delta Coast from
this evening through Friday morning. Water levels as high as 3 to 7
feet above the highest tide line continue to be possible through
this time; especially for the communities of Kwigillingok and
Kongiganak. The initial push of southerly to southwesterly winds
of 40 to 50 mph arrives this evening with the stronger more
significant push of 50 to 60 mph southerly winds arriving Thursday
evening. These winds slowly diminish through the day Friday as
flow turns more westerly and cold air works in off the Bering. As
this colder air works in during the day Friday into the Kuskokwim
Delta, warm southerly flow and rain continues for the AKPEN,
Bristol Bay, and the Lower Kuskokwim Valley into Saturday.

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

Little change from previous discussion.

Strong winds, precipitation and unseasonably warm temperatures
will continue through Monday over much of Southern Alaska as a
frontal system moves across the region. A major change in the
weather pattern late Monday and into Tuesday will see Southerly
winds give way to a more northerly component across much of
Southern Alaska as an Arctic airmass dips southward into the lower
half of the state. Much lower temperatures are expected across
much of Southern Alaska by Tuesday.

A very strong longwave ridge along the U.S. and Canadian west
coast, coupled with a deep longwave trough with associated closed
low and frontal systems is expected to be moving up into the
northern Bering Sea and up into far northeastern Russia. Strong
pressure and temperature gradients between these two systems will
be very impressive even by Alaskan standards. The strong pressure
gradient setting up along this boundary, plus at least two
distinct stronger areas of low pressure that will move north along
it, will support strong southwest winds, initially over the
eastern Aleutians and Southwest. Stronger winds could also affect
parts of Southcentral on Sunday as the second low moves up from
the Pacific into Southwest. Heavy precipitation along the main
frontal zone is expected as deep moisture will help support rather
intense precipitation rates for much of Southwest and later
Southcentral compared to what is typically possible for late
January. Temperatures in many areas of Southwest close to sea
level will likely initially be warm enough for rain at lower
elevations, and this will likely also be the case as the front
shifts into Southcentral between Sunday and Monday. There could be
a transition over to snow across both Southwest and Southcentral
as cooler air begins to move in behind the front between Sunday
and Monday.

&&

.AVIATION...

PANC... Scattered rain and snow showers are expected later this
morning through the late afternoon causing brief periods of MVFR
to VFR conditions. Southerly to southwesterly winds late this
afternoon through Thursday evening with gusts ranging from 20 to
30 knots are expected.

&&

$$