Gale Warning 377, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
444 PM AKDT Wed Apr 10 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3:
This afternoon through Saturday)...

The forecast generally remains on track, with a few minor changes
to reflect new trends in model data. Our primary short-term
hazards continue to be gusty winds and localized areas of moderate
to heavy snowfall, from Thursday morning through Friday. A Winter
Weather Advisory remains in effect for Broad Pass from early
Thursday morning through early Friday morning, though snow amounts
have been slightly reduced with this latest forecast package.

Diving into the details... a new low develops today along a front
that is currently draped across the Eastern Bering Sea and
Southwest Alaska coast. This new low advances towards Kotzebue
Sound through Thursday, pushing its front into Southcentral Alaska
and bringing a gusty and wet day to the region. With the low
strengthening as it moves towards Kotzebue Sound, a tightening
surface pressure gradient will lead to gusty southeast winds. The
strongest winds are expected in Anchorage, Palmer, and the Copper
River Basin, where gusts as high as about 40-50 mph are currently
forecast from Thursday afternoon through Friday morning.

Meanwhile, the heaviest precipitation is expected near Broad Pass
and along the north Gulf coast, where southerly flow will lead to
upslope enhancement along the mountains. There remains some
uncertainty with whether Anchorage and Matanuska Valley will see
any precipitation with this system. The generally southerly flow
is not ideal as moisture will wring out along Kenai Peninsula, but
there may be enough of a southwesterly component for precipitation
to stream up Cook Inlet and reach Anchorage/Matanuska Valley.
Even if any precipitation falls, not much is expected. There is a
small chance that we could inch closer to making this year
Anchorage's number 2 snowiest winter, but any snow that does fall
will likely melt due to near-surface air temperatures near
freezing.

By Friday morning, the start to a cooling and drying trend as an
incoming shortwave spins up a weak triple point low in the Gulf
and gradually shunts the lingering front into Southeast Alaska.
This incoming shortwave could bring a bit more snow as showers
move across Western Kenai Peninsula, Anchorage, and the Mat-Su
Valleys, but precipitation will generally taper off (except along
area mountains) after it moves through. Another arriving
shortwave on Saturday will help to reinforce the general cooling
and drying trend.

-KC

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA, BERING SEA, AND ALEUTIAN
ISLANDS (Days 1 through 3)...

Satellite imagery shows an elongated plume of Pacific moisture
extending from Nunivak to the Philippines. At the surface there
is a 966 mb low north of Attu and a wide spread pressure gradient.
Expect windy and wet conditions. However, this low will rapidly
move inland late Thursday and northwesterly flow will influence
the Bering. As that front moves inland the precipitation axis will
shift over SW AK. The thermal profile suggests another batch of
snow for Southwest AK. The enhanced pressure gradient will persist
as this system moves inland, so also expect blowing snow and
gusty winds. This front reaches the Alaska Range by late Thursday.
Snowfall amounts of 7 to 10 inches are possible for the Kuskokwim
Delta, 4 to 8 inches for the Kuskokwim Valley, and 9 to 13 inches
for the Western Capes of Bristol Bay through Thursday. Wind gusts
of 35 to 50 mph along the coast could result in blowing snow
reducing visibility to as low as one half to one quarter mile.
Given the expected conditions, multiple Winter Weather Advisories
and Blizzard Warnings remain in effect across Southwest Alaska.

&&

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

By Sunday morning, ridging will be built over the Bering Sea,
with an axis of the ridge extending over Southern Alaska. This
pattern will work to suppress most active weather that attempts
to build over our region at that time. Into the workweek, models
have suggested that influence from this ridge will grow, and shift
slightly to the northeast, further increasing its clearing effect
over Southern Alaska. Given this movement of the ridge, models
are suggesting a trough and surface low pressure system will fill
in behind it, pushing into the Eastern Aleutians, Alaska Peninsula
and Southwest Alaska. This hasty breakdown of a ridge and
replacement with active weather is typical of some models, such as
the GFS, for Alaska, and currently the other model solutions are
not buying into how fast the low pushes northward. However, by
midweek, we may begin to see an end to the clear conditions for
the Alaska Peninsula, and begin to see some mid-level clouds
filling in over Southcentral.

-CL

&&

.AVIATION...

PANC...VFR conditions will persist. The Turnagain Arm wind will
begin to ramp up Thursday morning, peaking in the afternoon hours.
Southeasterly gusts will be nearing the 30 to 35 kts before
tapering down in the evening.

MTL

&&