Small Craft Advisory 45, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
500 AM AKST Sun Jan 14 2024

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

This mornings water vapor imagery shows the very tightly wound
occluded trough lifting north across western Alaska with trough
lifting across Southcentral. A secondary trough is also noted
moving eastwards across the AKPen with much drier air moving in
behind the trough. This will help to shut off perception later
today as that drier air works up into Southcentral resulting in
clearing skies and decent radiational cooling overnight tonight.

For this morning, scattered showers continue to push north across
the northern Gulf and coastal areas, and Prince William Sound ahead
of the front. Wind observations and radar returns indicate that the
front has passed north of Middleton Island, and surface low has
developed along the eastern Kenai. This low will track into the
Prince William Sound before stalling and gradually washing
out...which is slightly different from yesterday's consensus surface
low track. Showers should continue for much of the day for the
coastal mountains before winding down this evening. Looking west
towards Cook Inlet and points north...a band of light to moderate
snow has been tracking north up the Inlet and northern half of the
western Kenai this morning. This generally N-S oriented band has
stalled across the Turnagain and Knik Arms north into the Mat-Su
Valley. Snow has had a difficult time with a pocket of dry air below
900 mb and is struggling to saturate the boundary layer. In
addition, a convergent zone has set-up as southwesterly winds behind
the front interact with the Turnagain Arm winds. In response to this
interaction, the Turnagain Arm winds have bent into western
Anchorage and have helped to reinforce the dry air in the boundary
layer. Temperatures have also warmed 10 degrees at the surface as
winds help to mix the lowest 100mb. Despite the surface warming, the
layer is so shallow that snow will not have time to melt before
reaching the surface so precipitation type should remain snow this
morning for the Anchorage Bowl, Eagle River, and up into the Valley.
As such, it still looks like only minor amounts are expecting for
these areas with accumulations generally less than an inch. The
Susitna Valley will see the highest accumulations today with up to
several inches of snow.

Precipitation will clear out later today and quiet weather will
return to Southcentral for several days as high pressure builds back
into the Gulf.

- PP

&&

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

Finally! The active stretch of weather is about to come to an end
for those not named the Kuskokwim Delta or the Western and Central
Aleutian Chain. Those areas too will also become quieter in the
weather department in due time.

Firstly, the low pressure system that brought the high winds to
Eastern Aleutian Chain and reduced visibilities due to snow and
blowing snow for the Pribilof Islands and Nunivak Island continues
moving northward over the Yukon Delta this morning. Last night,
Mekoryuk experienced 3 to 4 hours of visibilities reduced to 1/2
mile with an occasional drop to 1/4 mile with snow falling into
strong gusty westerly winds. Conditions have since improved
slightly with mostly 1 mile visibility. Bethel and Kalskag are now
getting in on the snow and the reduced visibilities as moisture
continues streaming eastward off the Bering Sea. Conditions should
really begin to improve later on this morning as the system
continues to pull away to the northeast into the central interior
of the state. However, cold air advection continues into mainland
Southwest and the Alaska Peninsula for most of the day today
which will help aid the chance for scattered snow showers for the
AKPEN and portions of coastal Bristol Bay. Any precipitation shuts
off in the afternoon as ridging begins to build into the AKPEN,
Bristol Bay, and the Lower Kuskokwim Valley tonight. With this
setup and warming temperatures aloft, fog could develop across
portions of Bristol Bay this evening and perhaps again Monday
evening.

Meanwhile, a low pressure system near Kamchatka continues to send
its front northeastward over the Bering Sea while sub-tropical
moisture and warm air is being drawn northward over the Western
Aleutians. The result of the interaction between the frontal
system butting up against the ridge building into portions of
mainland Southwest is a soaking rain for western Chain. The tail
end of the front will clip the Kuskokwim Delta tonight with more
snow showers and or rain/snow mix anticipated. This activity looks
to end Monday morning. The tail end of the secondary frontal
system will clip the Kuskokwim Delta again late Monday night into
Tuesday morning with another round of light precipitation. Most
activity ends across the Aleutians for Tuesday, with the
exception of maybe some light showers over the western Aleutians
as a weak wave lifts northward over the area. Conditions across
the AKPEN and mainland Southwest also become quieter for Tuesday
as a strong ridge of high pressure rules the roost over most of
the domain.

&&

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

By mid-week next week, an upper-level ridge will have moved over
Southern Alaska and the Bering Sea, suppressing active weather
across our region. While the high pressure is in place, a clear
and cool pattern will prevail for most of Southcentral and
Southwest Alaska. While the ridge is in place, models are keying
in on some pockets of energy swinging up and over the northern
side of the ridge, may swing back down south over Southcentral
beginning Wednesday and continuing into the weekend. Timing these
shortwaves is challenging as there is a lot of model spread
regarding where/when exactly these waves move through, however
potential impacts of these waves are still decipherable. Gusty
winds and colder temperatures moving south will likely be the
impact felt for Southcentral and Southwest through the latter half
of the week into the weekend. Areas of outflow winds develop
along the Alaska Peninsula and Southcentral Coasts, with gale
force gap winds through the Barren Islands and Shelikof Strait and
along the Alaska Peninsula Coast into the Eastern Aleutians
developing for Thursday and diminishing Friday. By Saturday
afternoon, there is the potential for a new low to approach
coastal Southcentral from the Gulf of Alaska, however uncertainty
on this system remains high.

-CL

&&

.AVIATION...

PANC...Light snow will persist throughout the morning, keeping
conditions predominantly MVFR with periods of IFR possible. There
is a chance for snowfall to linger into this afternoon in which
case conditions would remain lower at MVFR. However, VFR
conditions should return once the snow tapers off. A gusty
Turnagain Arm wind developed early this morning and is expected to
diminish by later this morning. By this evening and for tonight,
high pressure building into the area will promote light winds and
the potential for fog.

&&