Brisk Wind Advisory 33, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
455 PM AKST Thu Feb 29 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Tonight
through Sunday morning)...

Similarly to yesterday, gusty conditions and cooler temperatures
are ongoing across Southcentral Alaska this afternoon. A 982 mb
low continues to churn over the northern Gulf roughly 160 nm to
the east of the city of Kodiak. Meanwhile, a cold airmass remains
in place across the region with 850mb temperatures ranging from
10 below to 25 below Celsius. High pressure centered over the
southern ALCAN border has contributed to an enhanced pressure
gradient across Southcentral with gusty northerly winds spilling
out of the Chugach Mountains and Talkeetnas. Winds have routinely
gusted in excess of 30 mph from Talkeetna, southwestward. A
Matanuska wind continues to produce a narrow axis of northeast
winds gusting to near 40 mph across the Valley from Sutton to
Trunk Road into the Hay Flats. This has also resulted in areas of
drifting snow along the roads. Likewise, winds continue to drain
out of Resurrection Bay, Whitter, the Copper River Delta, and from
Thompson Pass into Valdez and Valdez Arm. Light snow has worked
its way into Whittier, but should taper off through the evening
hours. A wind chill advisory is in effect for Thompson Pass from
9pm this evening to noon Sunday, where cold temperatures at or
below zero are combining with winds gusting from 50 to as high as
60 mph. Resulting wind chills will range from the -30s to -40s and
below over the next couple of days.

Despite the Gulf low finally taking a southward turn on satellite
this afternoon, and a logical expectation of winds calming down,
a trough over interior Alaska is forecast to dip through
Southcentral on Friday with renewed winds. As mentioned in the
previous discussion, calmer conditions are finally anticipated
over the weekend, but this will also result in temperatures
dropping in the wake of overnight radiational cooling and
continued cold 850mb temperatures aloft. The coldest temperatures
from Willow down into the Anchorage Bowl will range from -5 to -10
degrees or colder Saturday and Sunday morning. The Copper River
Basin will see the coldest overnight low temperatures easily
dropping below -20 degrees from Paxton to McCarthy during the same
time span.

On a final note, the threat for extreme freezing spray will
continue to rear its ugly head over the Gulf. Extreme freezing
spray accumulations at a rate of 4 cm per hour or greater will be
possible through the Shelikof Strait and also west of the Barren
Islands, including Kamishak Bay through tomorrow.

BL

&&

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

The pattern across the Bering Sea continues to be steadily
progressive as a front in the Western/Central Aleutians is slowly
moving eastward. Southwest Alaska is in a steady state as cold,
dry air continues to flow into the area from the north, keeping
the area cold and clear, allowing for sunshine during the day. A
strong upper ridge continues to build over much of the Bering Sea
to the west of the deep troughing still in place over the southern
Mainland. Temperatures overnight in Southwest will continue to be
frigid due to the clear skies and northerly flow, with the Lower
Kuskokwim Valley to see the coldest temperatures, down to -25F by
the early morning Friday. This cold air looks to remain in the
area until kicked out by a shift in wind direction, potentially as
the warm front to the west approaches.

Speaking of, the warm front boundary that is currently situated
over the Central Aleutians is bringing a wave of initially
snowfall to the area, switching over to a mixed precipitation
(including snow, ice pellets, and freezing rain) behind the front,
with plain rain further behind that. Unalaska and the Pribilofs
have begun observing snowfall from this front, and the
aforementioned precipitation transition will occur slowly
overnight tonight. Depending on the speed at which warmer air
works into the area, more than a trace of ice accumulation at the
surface is possible for these areas due to the temporary freezing
rain pattern, but will eventually shift to a plain rain through
the day Friday. Less than a tenth of an inch of ice accumulation
is expected with this system. Across the eastern Aleutians,
precipitation should start as mostly sleet and snow this evening,
then begin to change to freezing rain later tonight before going
over to all rain as surface temperatures warm above freezing. A
similar transition is likely to take place as precipitation
spreads into the southern Alaska Peninsula starting late Friday
morning, but the transition over to rain or a rain snow mix will
likely take longer due to initially colder temperatures in place
and a further slowing of the front's progression. While there is
still uncertainty for timing of precipitation type transition,
areas around Cold Bay, False Pass and Nelson Lagoon could see the
wintry mix last all the way to Saturday afternoon until
temperatures aloft finally cool below freezing. Farther north
across the Pribilofs, gale force winds will initially lead to
areas of snow and blowing snow late tonight, but a transition over
to mostly sleet is likely as the warm nose aloft moves in on
Friday. See the Winter Weather Advisories that remain in effect
for all three of these regions for further details.

Between Friday and Saturday, the front will continue to move
slowly east as it finally begins to approach the Southwest coast.
Temperatures over Southwest should finally begin to warm up into
the 0s to 10s above by Saturday as the Arctic air mass retreats.
Light snow chances will also return to Bristol Bay and the
Kuskokwim Delta by Saturday afternoon as the weakening Bering
front approaches the coast. Meanwhile, another low will cross the
Aleutians into the western Bering with another round of rain and
snow pushing across the western Aleutian Chain on Saturday.

CL/AS

&&

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

The upper level forecast models show marked changes in the
amplitude of the troughs and ridges across the region through the
forecast period. Confidence remains mixed due to the speeds and
tracks of the smaller scale surface features across the State. The
ridge that held over mainland Alaska weakens and slips into the
Canadian Provinces by Thursday. The Bering upper low continues its
expansion into the Mainland, aided by shortwaves moving through
the pattern. This diminishes but does not completely end the flow
of Arctic air draining over the Interior into the Southern parts
of the state. A well developed low and frontal system push into
the Western Coasts Monday, but becomes diffuse as it enters the
Interior. Gusty Winds and widespread snow are expected. Another
well developed low and front track over the Aleutians from the
North Pacific Tuesday, and works its way across to Southcentral
Alaska for Thursday. Gusty winds, with areas of gale force gusts
over the Central Aleutians Tuesday and Wednesday. Precipitation
starts as snow, but changes to mixed rain and snow to rain along
the Aleutians, Alaska Peninsula into Kodiak Island. Mostly snow
occurs over Southcentral Alaska through Thursday.

Kutz

&&

.AVIATION...

PANC...VFR conditions and strong northerly winds will persist
through Friday afternoon. Gusts are expected to generally range
from 25 to 30 knots with an occasional 35 kt gust possible.

CC

&&