Gale Warning 293, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
458 PM AKDT Sun Mar 17 2024

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

Moist, upper level southerly flow coupled with a surface low
located in the Gulf of Alaska, has helped to maintain showers in
the Prince William Sound area and a weak deformation band oriented
along Cook Inlet, stretching north into the Susitna Valley. As
the low nears the northern Gulf coast tonight, the deformation
band will begin to shift orientation more north-south and
gradually nudge eastward. Snow is expected to be light tonight
with up to two inches for western Kenai Peninsula, the MatSu, and
Anchorage. Localized areas could have up to four inches over
higher elevations and where upslope flow is favorable (Anchorage
Hillside, Skwentna and the Parks Highway north of Talkeetna).
Pockets of a rain and snow mix is possible before midnight for
the Knik River Valley and from around Willow through Talkeetna
before midnight. Though precipitation is expected to be light,
model soundings suggest the prime opportunity for snow to
accumulate will be early Monday morning.

A ridge of high pressure will build in from the western Gulf to
the northern Gulf later on Monday that will help weaken the low
and clear precipitation by Monday afternoon for all of
Southcentral. Looking ahead through at least midweek, quiet
weather is expected as high pressure dominates Southcentral. The
only exception would be for the western portion of Kodiak Island,
where a slight chance of precipitation is possible Wednesday
morning as a front reaches the southwestern Alaska coast and
weakens.

&&

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

Current satellite shows an approaching low south of the Western
Aleutian Islands and surface observations report snow from this
low falling in Adak Island and Atka. This low will move through the
Central Aleutians Monday and Tuesday bringing widespread
precipitation, continued freezing spray and gale force winds
across the Islands ahead of its frontal passage. Southerly gap
winds will develop early tomorrow morning and increase rapidly by
the late morning hours ranging from 40 to 50 mph in the Eastern
Aleutians and AK Pen in the wake of the front. Also Monday
morning, easterly wind gusts in the Pribilof Islands ahead of this
approaching fronts passage will produce 2 to 5 inches of snow,
blowing snow, wind gusts ranging from 30 to 40 mph and visibility
as low as 1/4 mile. A Blizzard Warning has been issued for these
conditions Monday late morning through late afternoon. As the
front reaches Toksook Bay and Nunivak Island, visibility ranging
from 1/2 to 1/4 mile and gusty winds from 30 to 40 mph Monday
evening into Tuesday morning, in addition to up to 4 inches of
snow accumulation, are expected. A Winter Storm Warning has been
issued for these conditions. Behind the warm front's passage, snow
will transition to rain and sea ice will begin to retreat
northward. Warm southerly to southwesterly winds will continue
through mid-week resulting in high temperatures reaching 40
degrees in much of Southwest Alaska. Another chance for
precipitation arrives Wednesday in the Central Aleutians.

&&

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

The long term forecast remains largely unchanged. The upper level
pattern will be highly amplified, featuring deep troughing over
the Bering Sea and Aleutians and a stout ridge across much of
Mainland Alaska and the Gulf. This large scale weather pattern
will favor warmer than average temperatures across Southern
Alaska.

While drier weather and lighter winds are expected for
Southcentral Alaska under the ridge, much more active weather will
be in store for the Bering Sea, Aleutian Islands, and Southwest
Alaska as several storms move through. The biggest challenge in
the long term will be honing in on the track and evolution of
these storms, which will then inform where the strongest winds
(likely to gale force or higher) and heaviest precipitation are
expected.

Beginning early Thursday morning, a complex low with
multiple centers will slide north across the Bering Sea.
Confidence is low with the location of the embedded low centers,
but models seem to be converging on stronger winds surging across
the Eastern Aleutians, Alaska Peninsula, and Southwest coastline
through Thursday. The next storm arrives Friday from the North
Pacific, with decent agreement that surface pressure will drop to
about 970-980 mb. While the low looks to occlude as it moves into
the Bering Sea, parts of the Aleutian Islands and Bering Sea could
still see gales along the front, as well as moderate to heavy
precipitation.

Forecast confidence decreases by late Friday, with the question of
whether the aforementioned low is strong enough to completely
displace the ridge extending across much of Alaska and the Gulf.
If the low is strong enough to displace the ridge, its front will
bring stronger winds and widespread precipitation to Southcentral.
If the ridge holds strong, the front will remain west of Kodiak
and allow drier and calmer weather to persist through the weekend.

- KC

&&

.AVIATION...

PANC...VFR conditions this afternoon will gradually deteriorate
back to MVFR by late this evening and into the overnight hours as
snow begins to move back into the area. Periods of light snow
will peak early Monday morning with a total snow accumulation of
1 to 2 inches. Expect VFR ceilings and drier conditions Monday
afternoon through the remainder of the week.

&&