Heavy Freezing Spray Warning 222, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
453 PM AKST Fri Dec 10 2021

.ANALYSIS AND UPPER LEVELS...
A deep vertically stacked low over the northern Gulf is beginning
to slowly exit off to the south and east. The bulk of snow
associated with the low center has moved offshore. Areas of
flurries or light snow linger over interior Southcentral as weak
upper level short-waves travel southward and low level cold air
advection begins. Pressure gradients along with the cold air
advection are leading to strengthening gap winds along the Gulf
and Prince William Sound coasts. The core of strongest cold air
advection is on the back side of the upper trough, from Southwest
Alaska southward to the Alaska Peninsula. This is leading to
widespread gusty winds across the region, with the strongest
winds out of bays and passes along the south side of the Alaska
Peninsula. Cold air advection across the eastern Bering Sea is
producing snow showers and gusty winds, with intermittent low
visibilities in snow and blowing snow from the Pribilof Islands
to Eastern Aleutians and Alaska Peninsula. Conditions are quiet
for the moment across the western Bering and Aleutians as a strong
upper level ridge builds in from the south and west.

&&

.MODEL DISCUSSION...
Models remain in good agreement with the large scale pattern over
the next few days. The forecast challenge will be the details of
winds and temperatures this weekend.

&&

.AVIATION...
PANC...VFR conditions will persist. The challenge for the forecast
will be winds. Low level cold air advection will increase low
level northerly winds tonight. However, not sure there is enough
forcing to mix these down to the surface. Gusty northerly winds
seem most likely during the day Saturday as the cold air advection
continues and likely overwhelms any low level inversion, resulting
in more vertical mixing of the wind.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 to 3: Tonight
through Monday morning)...

The low responsible for the most recent winter weather over the
Kenai Peninsula and much of the Prince William Sound area has now
migrated out into the northern Gulf, with snowfall now ended over
land for all but a few spots along the North Gulf Coast. Light
snow showers are also persisting over parts of the eastern Kenai
Peninsula, with snow also making it into Anchorage earlier in the
day with a weak northerly shortwave moving through. Another weak
wave aloft will drop across the Mat-Su Valleys from the Talkeetna
Mountains this evening, perhaps leading to renewed areas of light
snow or flurries that will result in little to no accumulation.

With the snow now ending area-wide, attention now turns more to
the major cold air outflow/gap wind event expected to unfold for
favored locations along the North Gulf Coast (Copper River Delta,
Valdez Arm, Passage Canal and Resurrection Bay) and more notably
along the northern Alaska Peninsula and around Kodiak. An Arctic
airmass will begin to make greater headway southward into much of
Southcentral and Southwest, increasing cold air advection along
the Alaska Peninsula and North Gulf Coast through Saturday. The
deep area of low pressure will remain situated over the Gulf
through the weekend as a northwest to southeast oriented upper jet
approaches the northern Alaska Peninsula and Kodiak, keeping the
pressure gradient along the coast exceptionally strong and aiding
forcing/subsidence associated with the intruding cold air mass.
This will produce extremely strong winds along bays and passes out
along the Alaska Peninsula, with Hurricane force winds developing
through parts of Shelikof Strait and near the Barren Islands
tonight. Winds will not be quite as strong around Kodiak Island,
but peak gusts are again expected to reach near 80 mph beginning
late tonight and lasting throughout the day Saturday. See the High
Wind Warning that has been issued with this package for further
details. The extremely strong winds coupled with temperatures
cooling into the 10s and 20s will cause areas of very heavy
freezing spray, again most notably near the Barren Islands and
Shelikof Strait. Mariners in the area should use extreme caution
as long as these conditions persist, with the more significant
winds and heavy freezing spray expected to continue well into
Sunday.

The main story away from marine areas will be the very cold
temperatures filtering in with the return of the Arctic air. Winds
will initially be strong enough to hold temperatures above 0F for
most areas through Saturday, but the cold will eventually win out
as skies begin to clear out and winds calm, helping lows to drop
in the -0s to -10s for lows on Sunday morning and again on Monday
for most of the interior. Low wind chills are possible where
winds remain higher, especially through Isabel and Broad Passes.

&&

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

A break in the active weather is expected for Southwest Alaska
over the next couple of days as upper level ridging slowly moves
in from the west. This will allow for a gradual easing of the
brisk northwesterly winds over the next couple of days. Cold
temperatures are also expected with inland portions remaining
subzero. The likelihood for snowfall will continue to decrease
across Southwest Alaska, except for areas along the Alaska
Peninsula as convective snow showers will continue to move
southeastward across the Alaska Peninsula.

&&

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

An active weather pattern remains across the Bering/Aleutians over
the next few days. Strong northwesterly winds will allow for this
cold air advection pattern to continue producing ocean-effect
snow showers across the central to eastern Bering/Aleutians. The
strongest winds will be across the coastal waters south of the
Alaska Peninsula and Eastern Aleutians Saturday and Sunday as
widespread storm force winds are expected with hurricane force
gusts in areas prone to funneling from the northwest. The next
front will enter the western Bering/Aleutians Saturday night and
gradually move eastward to the eastern Bering/Aleutians Monday
afternoon and then stalling out over the area. This front will
bring warmer temperatures for much of the Bering/Aleutians due to
warm air advection in the wake of the front. This front will also
bring a mix of rain and snow to the Aleutians which will gradually
change from snow to rain from west to east.

&&

.MARINE (Days 3 through 5/Monday through Wednesday)...

Expect active weather across the Bering Sea, Aleutians, and
Southwest coast for the coming week, with fast moving storm
systems and rapidly changing conditions. Storms will generally
track from southwest to northeast across the Bering Sea.
Expect widespread gale force winds across the region, with
potential for smaller areas of storm force winds. The Gulf
of Alaska waters look much quieter, with some weaker systems
passing nearby.

&&

.LONG TERM FORECAST (Days 4 through 7/Tuesday through Friday)...

It looks like a very stormy week across the Bering Sea, Aleutians,
and Southwest Alaska. The general storm track will be from
southwest to northeast across the Bering Sea. Progressive flow
aloft will lead to fast moving systems and rapidly changing
weather. The main threat to Southwest Alaska will be snow and
blowing snow, especially along the coast. For the Bering Sea and
Aleutians, warmer air accompanying these systems will generally
produce rain early in the week, while a shift in upper flow later
in the week could cause a change back to snow. Nonetheless,
expect periods of strong winds with each of these systems.

Southcentral Alaska will start out quiet, with perhaps a glancing
blow of light snow Monday night-Tuesday from a low crossing the
southern Gulf of Alaska. Weather will become more active for the
second half of the week as upper level flow shifts and storms
crossing the Bering continue eastward across mainland Alaska.
This will bring additional chances of snow. With the strength of
the upper level flow, each shot of snow would be brief. As for
temperatures, the week will start out in the deep freeze, but
would expect moderation of temperatures as we head through the
week.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Warning 171.
MARINE...Storm 131-137 150 155 178
		 Hurricane Force Wind 130 138
		 Heavy Freezing Spray 119-125 129-165 180-185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SEB
SOUTHCENTRAL ALASKA...AS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ED
MARINE/LONG TERM...SEB