Gale Warning 216, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
506 AM AKDT Thu Mar 17 2022

.ANALYSIS AND UPPER LEVELS...

A polar low in Bristol Bay continues its southward trajectory,
spending the day crossing the AKPen and pushing into the North
Pacific. This system essentially re-amplifies as it merges with a
secondary North Pacific low, stalling briefly in the southern Gulf
and then pivoting north/northwest wards tracking towards Kodiak
Island. The cold Arctic air being pulled southwards across the
eastern Bering will inevitably wind up wrapping around the low
and pushing lingering colder air into the Gulf. East-west oriented
upper-level ridging moves over the Copper Basin and northern
Susitna Valley by tomorrow morning and gets shunted off to the
north as the aforementioned North Pacific low enters the Gulf.
Longwave upper level ridging has been, and will continue
bombarding the western Bering through the at least the short term.

&&

.MODEL DISCUSSION...

Overall, models are in relatively good agreement through the short
term. There are some weak surface lows sporadically placed withing
a trough in the northern Gulf, but otherwise consensus is fine
through Friday night. A North Pacific low pushing towards the
southern Gulf is giving the models a difficult time specifically
with center location and system strength. General track is being
handled well across all solutions, with some light variations in
speed. The NAM/GFS are working in tandem for the most part, while
the Canadian and EC are lagging behind, the EC being placed
furthest east.

&&

.AVIATION...

PANC...Mostly VFR conditions and light winds will persist.
Conditions may to drop to marginal during the morning hours and
then improve again for the afternoon and evening hours. Cloud
ceilings will likely be at or just below 5000' through much of the
afternoon before raising this evening.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Thursday through
Saturday night)...

An upper-level shortwave and associated surface trough will move
from the northern Gulf this morning into the interior of
Southcentral by Thursday evening. As it does, precipitation will
spread from the northern Gulf and Prince William Sound north and
west across Cook Inlet and into the Susitna Valley. As this wave
and the precipitation both progress north and west, a surge of
cold air wrapping into an upper low out west will move out of the
western Gulf northeast into the Cook Inlet region. This cold air
advection moving in aloft should allow for the precipitation to
fall as snow showers, with a lingering rain/snow mix possible
along the immediate coast. The surface trough and associated push
of cold air will stall along the coast and over northern Cook
Inlet. Thus, chances for any snow showers will quickly diminish
across the Mat-Su Valleys and Copper River Basin, with the
Talkeetnas and Alaska Range seeing the best chances.

By Thursday evening, the upper-level low over the AKPen slips
south. As it does, a North Pacific low will lift north into the
southern Gulf, preceded by two distinct upper-level waves
associated with the frontal system of a developing surface low in
the Southern Gulf. The first of these will move to the coast late
Thursday, keeping precipitation going along the coast, especially
along the eastern Kenai Peninsula coast and western Prince William
Sound given the persistent easterly flow aloft. The second wave
will move from the eastern Gulf across the northern Gulf and to
the western Gulf by Friday afternoon. This feature will move in
tandem with the surface front which will act to not only increase
northerly gap winds, but bring more precipitation in the form of
rain/snow along the coast and snow farther inland and at
elevation.

By Friday, the front advances to Kodiak Island, where a northerly
wind should hold temperatures in the lower to mid 30s. Thus,
precipitation is expected to fall as wet snow across the island,
with rain eventually moving in around Kodiak City Friday
afternoon or evening as warmer air pushes to the coast. Still, 3
to 6 inches of snow are possible with this system.

Elsewhere, intermittent clouds are expected across interior
Southcentral. The east-northeasterly flow aloft should keep the
bulk of the precipitation along the coast. The exception to this
may be upslope areas of the Glenn Highway around Eureka where
occasional light snow is possible.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 through 3: Today
through Saturday night)...

Steady light snow showers continues over much of Southwest AK
early this morning, while a stacked vertical low crosses the
Alaska Peninsula for the western Gulf into noon today. Moisture
from the northern Gulf channeling west and across the Alaska Range
enhances clouds rotating through Bristol Bay including Iliamna,
Koliganek and Platinum. Strong wind gradient over the coastal
waters will force the aforementioned low into the deep North
Pacific by this evening. This same low will become absorbed into
the next North Pacific low approaching the Gulf by tonight,
leading to upper short waves rotating across parts of the lower
Kuskokwim Valley and over much of Bristol Bay Fri night through
Sat night. This pattern will continue to bring unsettled weather
and periods of light snow there. Cold polar air will continue to
push through the region especially to the west of the lower
Kuskokwim through the weekend, where low temperatures will fall
to zero to 10 above for the next few nights. Brisk northerly winds
will persist over much of the region through the weekend.

&&

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

Cold air from the Arctic will persist across the Bering with
areas of gales across the northern and eastern Bering with the
strongest winds south of the Eastern Aleutians and AKPen, while
potentially storm force gusts out of bays and passes continues through
at least Friday and possibly into Saturday. Another shortwave
with cold air will move out of Siberia and push southward across
the Bering late today through Friday producing a wide swath of
gales across much of the Bering through Saturday. Otherwise
expect snow showers south of the ice edge across the northern
Bering and extending south to the Aleutians and AKPen. Expect
severals inches of snow across the Eastern Aleutians and AKPen
over the short term as cold air continues to produce snow showers
through at least Saturday.

&&

.Marine (Days 3 through 5: Saturday through Monday)...

Gulf of Alaska: A well developed low exits the Southwestern Gulf
as a second well developed low enters the Southcentral Gulf on
Sunday. The second low moves to the Southwestern Gulf for Monday.
Forecast guidance is good. The wind wrapped first low brings high
end gales across the Gulf and through Cook Inlet, Barren Islands
and Shelikof Strait, diminishing Sunday. Gale force gap winds
continue along the Alaska Peninsula through Monday. The wind
wrapped second low spreads high end gales over the Gulf with
possible storm force winds South of Kodiak Island through Monday.
Seas to 12 feet over the Northern Gulf and to 18 feet across the
Southern Gulf through Monday. Freezing spray possible South and
West of Kodiak Island Saturday.

Bering Sea: The Western Bering high pressure continues its
Southward track, with its North side ridge moving across the
Bering through Monday. Several troughs move over the Eastern
Bering through Monday. Widespread high end gales move over the
Eastern Bering, Aleutians and Alaska Peninsula, diminishing over
the Bering Monday. Gap winds persist along the Pacific side of the
Aleutians and Alaska Peninsula through Monday. Seas to 20 feet
over the Bering side of the Central and Eastern Aleutians and
Alaska Peninsula through Sunday, subsiding. A front approaches the
Western Aleutians and Bering for Monday. Gusty winds increase to
widespread high end gales across the Western Aleutians and Bering.
Seas building to 20 feet for Monday. Freezing spray expected in
open waters over the Western and Central Bering through Saturday.

&&

.Long Term Discussion (Days 4 through 7: Sunday through Wednesday)...

The latest operational model runs and ensemble means are decently
clustered with the evolution and progression of the synoptic
scale features, but diverge in the specific details towards the
end of the period. Models seem to have a general consensus will be
a long wave pattern through early next week, with a broad trough
persisting over Mainland Alaska through Monday.

Meanwhile, an upper level low will be positioned somewhere in the
central Gulf that will pinwheel a series of shortwaves and
associated surface lows northward. Even though there is a good
amount of discrepancy and variability with these shortwaves, most
of the precipitation will be concentrated through the Panhandle
and up into the southern coasts. Much of the mainland should be
relatively dry during the period, with the exception for potential
snow showers by late Sunday in the eastern interior. Otherwise,
temperatures are expected to be below normal across the coastal
areas and interior valleys, but trending toward normal next week.

Out west, a ridge of high pressure will build across the Bering
Sea. A reinforcement of cold air advection will help drive
northerly winds funneling through the gaps and passes of the
Alaska Peninsula and Eastern Aleutian Islands. Wrap around
moisture on the backside of the aforementioned upper low will
bring occasional snow showers into these regions later this week.
A drying trend commences on Monday as the ridge axis shifts over
the western mainland, while a gale force front extending from a
Kamchatka low moves slowly east across the Western/Central
Aleutians. From Tuesday beyond, there is considerable spread how
far the front progresses with a variety of solutions over the
Bering Sea and Gulf of Alaska.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning 119 120 131 132 138 150 155 165 170 171
					  172 178 179 180 181 185 351 352 414
		 Heavy Freezing Spray Warning 165 179 180 185 412 414
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KM
SOUTHCENTRAL ALASKA...TM
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
MARINE/LONG TERM...MK/MF