Gale Warning 180, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
527 AM AKST Tue Feb 13 2024

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

Southcentral is, and will remain trapped between the large upper
level ridge that is centered over the eastern Gulf of Alaska, and
the large, upper level trough in the Bering Sea. This strong
southerly flow will continue to pump warm air from the tropical
Pacific into Southcentral Alaska for a few more days. This means
that, while details will change some, the overall pattern will
not. The overall pattern will keep stiff southeasterly winds along
the mountains through Thursday. The details are that the
strongest winds will be along the Anchorage Hillside today where
there remains a High Wind Warning into this evening. These winds
will diminish this evening, but not shut off. Temperatures will
likely be warmest today, but will remain well above normal for
just about all of Southcentral through the remainder of the week.
In fact, Anchorage has already tied its record high for the day at
42 degrees as of 4 AM this morning.

The other big area of interest is around Kodiak Island where rain
and strong winds will persist through the day. The rain should
taper off tonight as the front finally edges west of the Island,
but another wave will move in by Wednesday night and bring more
moderate-to-heavy rain to the eastern half of the Island. Winds
will follow this same timing, with winds diminishing some tonight
into Wednesday, and then increasing again Wednesday night.

&&

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

While a satellite low pressure system dissipates over Bristol Bay
early this morning, a stronger low pressure system will move in
from the northern Pacific this morning. This will allow for the
steady stream of moisture moving into Southwest Alaska, and across
the Alaska Peninsula, to continue into at least Thursday this
week. Gusty winds across Southwest, driven by the low pressure
systems over marine Bristol Bay, will be strongest later this
morning and begin to slowly taper down, however not dissipating
entirely, through Wednesday afternoon. Gusts up to 55 mph are
possible in places between Igiugig and Lime Village later this
morning. By Thursday, a slightly weaker resurgence of winds
through the Kamishak Gap to Lake Iliamna area is expected, with
winds to reach 50 mph.

Temperatures early this morning are warmer than previously
expected, however a return towards cooler temperatures is expected
to begin by Tuesday night into Wednesday morning. As previously
mentioned, a long duration precipitation event for the Alaska
Peninsula and southern Bristol Bay continues through Thursday
night. Water equivalent precipitation amounts of 0.55 to 2.5
inches are possible. Through midweek, the types of precipitation
forecast across Southwest Alaska are as follows: snow for The
Kuskokwim Delta and Lower Kuskokwim Valley; rain for the Eastern
Aleutians and southern Alaska Peninsula; and lastly a rain/snow
mix for Bristol Bay and the northern Alaska Peninsula. The
aforementioned areas of rain/snow mix will see higher
precipitation totals than other Southwest Alaska regions due to
the orientation of the moisture feed. Contingent upon the
duration of snowfall and the ability for snowfall to persist at or
near freezing, Dillingham, Togiak, Pilot Point, and Port Heiden
are likely to see 4-8 inches of new snowfall through Thursday
morning.

The rest of the Bering and Aleutians remain fairly benign, with
the Western Aleutians seeing some on-and-off again showers today
and Thursday. Temperatures in this area are to remain at or near
freezing as well; however, due to the lack of significant incoming
moisture, little impact is anticipated.

&&

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

The long term begins with a stagnant upper-level ridge / trough
pattern east to west across the state. A 560dm ridge anchored over
the St. Elias Mountains Wednesday drifts northeast over the Yukon
for Friday before weakening and elongating as it continues a slow
push to the southeast over British Columbia. The broad trough over
the Bering and Aleutians also remains in place through the end of
the week. The result is a general west to southwesterly flow in
the mid levels across the southern Bering and Aleutians shifting
to a southerly flow from the western Gulf and Alaska Peninsula
north along the west coast of Alaska. Various shortwaves embedded
in the flow, along with a strong upper-level jet, are resulting in
a seemingly continuous parade of surface lows and troughs moving
from the North Pacific toward the Alaska Peninsula and Kodiak,
eventually moving farther north to the Bering Strait.

This storm track favors periods of heavy precipitation, in the
form of low elevation rain and mountain snow, from Kodiak Island
to the Alaska Peninsula and along the south-facing hills and
mountains of Southwest Alaska, due to upsloping. With multiple
surface lows tracking north across the Alaska Peninsula, strong
southeasterly gap winds and mountaintop winds are also likely,
with the strongest of the gap winds across the Alaska Peninsula
and through Kamishak Gap into the interior Bristol Bay region.
The southeasterly flow will also promote periods of showers
across the Kenai Mountains along with strong southeasterly gap
winds, mainly through Turnagain Arm and across the Matanuska
Valley.

The greatest uncertainty comes closer to the weekend, as models
try to weaken the ridge at differing times with the weaker, more
easterly positioned ridge and upstream trough becoming more
negatively tilted. This scenario would likely allow for storm
systems to move farther north into the Gulf of Alaska with
steadier precipitation moving toward the Southcentral coast.

-TM

&&

.AVIATION...

PANC...VFR conditions are forecast through Wednesday as high
pressure continues to build into Southcentral from the east.
Southeast winds across PANC, however, will remain gusty through
this afternoon and evening before a pressure gradient across the
region finally relaxes. The biggest uncertainty in the forecast
involves the timing of Turnagain Arm winds becoming down inlet and
subsequently replaced with lighter northerly, currently forecast
over PANC by early Wednesday morning.

-BL

&&