Gale Warning 787, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
453 AM AKST Sun Nov 3 2024

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

The main feature today is an elongated trough and surface low
along the north Gulf coast. The surface low will consolidate and
move into the western Prince William Sound as the main upper low
moves towards Cordova this evening before getting shunted off to
the east. These features, in addition to some cold air advection
from the west, will produce some light snow for most of the
region today. A Winter Weather Advisory is in effect for the
southwestern Kenai Peninsula, where a band of heavier snow will
set up this morning, lingering through late tonight. This is
mainly for the higher elevations north of Homer, but cold air
streaming through Kamishak Bay and across the southern Inlet may
be enough to produce a few inches in the Greater Kachemak Bay area
later today.

Monday will yield to calm and dry conditions as a shortwave ridge
moves overhead. Some sunshine is even expected in the afternoon.
This ridge is all due to warm air advection and building heights
to our south as a strong low continues to develop and move into
the eastern Aleutians. The system will occlude fairly quickly, but
a strong front will still push into Kodiak Island Monday evening,
the Kenai Peninsula Tuesday morning, and the Sound in the
afternoon. With the position of the low well to our south, a
strong down-Inlet gradient will develop, which should keep
Anchorage Bowl protected from the high winds moving through
Turnagain Arm, but strong winds can't be ruled out for the
Hillside, particularly Potter Valley. Very strong winds 75+ mph
are possible for the Portage area. Additionally, Cook Inlet
communities from Nikiski south to Kachemak Bay will have elevated
winds.

For precipitation type, most of the Kenai Peninsula is
expected to transition from snow to rain as the day progresses,
with snow levels rising to 1000 to 1500 ft. However, some blowing
snow is well in the realm of possibilities for Turnagain Pass
before conditions get too warm in the afternoon. That is if they
get too warm, intense precipitation can have a cooling effect and
result in snow despite warm air advection. Precipitation amounts
(liquid equivalent) with this front look to be in the 1 to 3 inch
range for the coastal mountains, with Whitter, Portage and
Turnagain Arm being the focus of the heaviest rain/snow.
Downsloping will mitigate the heavy precipitation for the Cook
Inlet areas and southern Mat-Su, but there is strong upper level
support so some rain and snow will likely still fall. A snow to
rain transition is expected as the front pushes north. After the
front moves through the gradient will relax some, and
precipitation will be mainly upslope on southern facing mountain
ranges.

&&

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

Model agreement continues to improve for approaching storm force
low, agreeing nearly unanimously on a track towards Cape Newenham
by Tuesday. Storm force winds are expected to reach the Eastern
Aleutians early Monday morning, spreading into the
southern/eastern Bering, Pribilof Islands and the Alaska Peninsula
by Tuesday afternoon. Small craft to high end gales will encompass
the remainder of the Bering Sea, as well as portions of Southwest
Alaska, primarily the coast, inland Kuskokwim Delta, and across
Bristol Bay through Kamishak Gap. Strong north to northwesterly winds
will also develop on the backside of the system on Tuesday as the
system tracks north. This system will pull moisture northwards,
as well as warmer temperatures and the southern side of the
Aleutians and especially the southern AKPen should see decent
rainfall as the front lifts through. As the precipitation pushes
north towards Bristol Bay, cold air already in place will allow
precipitation to start out as snow before transitioning over to a
rain/snow mix and then all rain as warmer air moves in.

&&

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

A broad upper level low stretches across the Bering into the
Interior of Alaska through the forecast period. The very active
weather pattern will occur across the Aleutians and Southern
Bering, Alaska Peninsula, Kodiak Island and the Southcentral
Coastal zones into the weekend. The ECMWF / GFS blend continues to
handle strengths and tracks of the systems through most of the
forecast, with model means picking up the slack by Saturday.
Opening the surface weather forecast is the remnants of the former
tropical system Kong-Rey moving over the Eastern Bering and
Western Alaska coastal zones. Precipitation will start as snow
across Southwest Alaska before a short period of mixed rain and
snow or freezing rain slips inland around Bristol Bay. Chances of
coastal flooding are highest along the Bristol Bay coast through
Wednesday. Gusty winds less than gale force spread along the AKPEN
coast, Kodiak Island and across the Southcentral coasts. Areas of
gusty winds move across the Bering through Thursday. Locally
heavy rains are expected all the way over to the Canadian Border,
with snow likely at higher elevations and further inland.

A second well developed low and frontal system glide along South
of the Aleutians before curving towards the AKPEN and Kodiak
Island and Southcentral zones on Thursday. Gale force winds move
into the Kodiak Island Waters late on Wednesday, the Barren
Islands and Kamishak Bay, and the Eastern Kenai Peninsula and
Prince William Sound Thursday before diminishing to widespread
less than gale force on Friday. In the Far West, a third
developing low approaches the Western Aleutians late Thursday, and
closes in on the Western and Central Aleutians through Saturday.
Gale force winds and another round of locally heavy rains spread
into the AKPEN for Saturday.

&&

.AVIATION...

PANC...VFR conditions and light winds will persist through early
this afternoon. Light snow will then approach from the south and
east, most likely reaching the terminal between 22Z and 02Z,
though there remains some uncertainty with timing. There is a
chance of mixed precipitation right at the start, but confidence
is increasing that precipitation should quickly go to all snow as
the low levels become saturated. Snow will then persist through
much of the day, before tapering off late tonight. Snow intensity
will be light for the entire event, suggesting MVFR to IFR
conditions will prevail.

&&