Gale Warning 116, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
449 PM AKST Sat Feb 5 2022

.ANALYSIS AND UPPER LEVELS...

An expansive 976 mb low is moving north into the Gulf this
afternoon. Rain has been ongoing across Middleton Island for the
entire day, and the precipitation shield is moving into Cordova. A
separate wave that brought a few tenths of an inch of snow to
Anchorage overnight has shifted north into the Susitna Valley
making for improving conditions with a very narrow area of
sunshine in between the two systems moving into the southern
Susitna Valley. The low will be tracking just east of Cordova,
near Cape Suckling, with coastal rain and mountain snow expected
for the southern and eastern Copper River Basin.

Despite all of the cloud cover over Southwest Alaska, no
precipitation is occurring, just some fog from Naknek to New
Stuyahok. Skies are gradually clearing around Lake Iliamna, and
have remained clear over much of the southern Kuskokwim
Mountains. A mesolow is swirling the typical stratus across the
southern Bering southwest of the Pribilofs, with a stronger low
tracking well west of Shemya.

In the upper levels, broad troughing remains in place over much of
the Bering. A closed low is following behind the surface low
moving into the Gulf, becoming negatively tilted. Much of the jet
energy associated with it is exiting to the east.

&&

.MODEL DISCUSSION...

The models remain in fair agreement through Monday afternoon. A
pair of lows entering the Gulf Monday night and the second on
Tuesday night continue to track through the "Kodiak Triangle", a
designation given to the waters between Kodiak Island and the
Shumagins where if the center of the surface low is forecast in
the models to track through that area, the models have a very hard
time coming into good agreement on just about anything until right
before the event begins. That is the case this time. In the
shorter-term, the low currently entering the Gulf is finally
getting some clarity, with the low moving from off of Kodiak
Island now to near Middleton Island late tonight, then gradually
turning westward into western Prince William Sound while
weakening. This track gives good indication for some light snow to
break out from Anchorage north Sunday night into Monday morning.
Forecast confidence is a bit above normal.

&&

.AVIATION...
PANC...VFR conditions and light northerly winds will persist into
Sunday. Some slight wind shear has been reported around the
terminal today, but has been marginal. Any wind shear will end
this evening. Light snow and associated MVFR to occasional IFR
conditions may develop as early as mid-afternoon on Sunday and
will persist into Monday morning. 1 to 3 inches of accumulation
are expected.

&&

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

Low-level ridging between storm systems has treated the Cook Inlet
region to a brief gap in the clouds and a bit of sun today.
However, the clouds are already returning as they make their way
over the coastal mountain ranges. Radar returns are already
materializing from the next storm system for Southcentral as an
elongated North Pacific low enters the Gulf. The elongated nature
of the low creates some uncertainty in its forecast track,
however there is increasing confidence that it will be centered south
of Cordova on Sunday morning before turning northeastward and
moving inland. As a result, continue to expect the bulk of
precipitation to sweep northward from Cordova early Sunday
morning across eastern Prince William Sound to Valdez and into
the Copper River Basin by midday. Near the center of the low,
temperatures will be warm enough for rain. Thus, mostly rain is
expected for Cordova and much of the Gulf coast initially. As the
low begins to exit eastward and track inland, colder air will
begin to move in from the west and the airmass will modify,
meaning by Sunday afternoon coastal regions may begin to
experience a mix of rain and snow. Valdez and the Copper River
Basin can expect all snow throughout the duration of the event. By
Sunday night, the low moves ashore and the upper-level shortwave
exits north and east, leading to precipitation decreasing in
intensity.

Meanwhile, an Arctic trough digs southward across western Alaska
and the eastern Bering Sea, bringing a frigid airmass to Southwest
Alaska. A weak shortwave sitting over the Southwest currently will
be shunted eastward as a result, arriving over Southcentral late
Sunday. The trough will tap into some of the cold air and help
produce areas of light snow Sunday night and somewhat lower
temperatures for Monday. This looks to bring 1 to 2 inches of snow
broadly across Anchorage to the Mat-Su, with lighter
accumulations possible across the northern Kenai Peninsula.

Following this, amplified flow will cause the next storm, another
elongated low moving out of the Pacific, to track further west.
The low is generally expected to track near Kodiak Island on
Monday and up to the Kenai Peninsula Monday night, bringing
another round of precipitation, primarily rain, to the Gulf coast.
On its heels looks to be yet another low, likely stronger, with
its front entering the western Gulf on Tuesday. While details
remain uncertain, warmer air looks to be on course for
Southcentral.

&&

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

Benign conditions will continue over most of the Southwest to
start out this evening as an area of weak winds aloft helps keep
the region outside of the prevailing storm track during the next
couple days. Some areas of low stratus and fog persist over
Bristol Bay and the Kuskokwim Delta, but this lingering moisture
should clear out from north to south through tomorrow morning as
cooling/drying northerly winds pick up with the passage of a
strong cold front. A bitterly cold, Arctic air mass will spread
south behind this front as an Arctic trough deepens and eventually
pinches off into a closed polar low overhead, with low
temperatures dropping down into the -10s to -20s across the
Kuskokwim Delta and Middle Kuskokwim Valley. Offshore winds up to
20 mph developing over mainly the Kuskokwim Delta will support
wind chills dropping to as low as -50F, particularly where
coinciding with morning low temperatures on Monday and Tuesday. A
Wind Chill Advisory has been issued and will go into effect
Sunday evening for the Kuskokwim Delta with confidence now higher
for dangerously cold wind chills.

Looking towards Tuesday, forecast confidence begins to decrease
once again as models struggle to handle the interaction between
the aforementioned polar low, a longwave ridge developing over the
Gulf, and a series of lows moving up in between these two
synoptic features. The first low is likely to move just east of
the Alaska Peninsula as it heads into Southcentral from Monday
night into Tuesday morning, with increasing potential for a band
of snow to move north into eastern portions of Bristol Bay and
the Middle Kuskokwim Valley on Tuesday morning. However, the
location of any accumulating snow will depend on how far north and
west the low moves, which remains somewhat uncertain at this
point. Another much larger system will approach the Alaska
Peninsula by Tuesday evening with potential for another widespread
round of snow, though details for timing and any impacts are even
less clear by this point in the current outlook.

&&

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

A "no flow" pattern in the upper levels is keeping things about as
quiet as it gets across the Bering, with little impactful weather
ongoing aside from widely scattered rain and snow showers wrapping
around a pair of mesoscale lows near the central Aleutians.
Conditions will become a bit more active on Sunday as northeast
flow develops behind an Arctic front moving southwest with time,
sending temperatures down into the 10s and 20s across the Aleutian
Chain and as cold as the single digits for the Pribilofs for much
of Monday and Tuesday. Northeast winds increasing to around 30 kts
over open water coupled with these increasingly cold air
temperatures will create areas of heavy freezing spray that will
expand southwest and well away from the ice edge with time as
temperatures at the sea surface cool through at least Tuesday. In
addition, expect increasingly more widespread snow showers to
develop as the Arctic air mass moves over open water and picks up
moisture from the Bering, especially across the Pribilofs and
western Aleutians for both Monday and Tuesday.

&&

.Marine (Days 3 through 5: Tuesday through Thursday)...

Gulf of Alaska:

A weakening low near Prince William Sound on Tuesday morning will
maintain high end small craft winds with gale force gusts and
seas close to 20 ft south of Middleton Island. As the low moves
inland Tuesday afternoon, expect winds less than 35 kts and seas
less than 20 ft. A well developed North Pacific low with an
associated front approaches near Kodiak Island late Tuesday night.
There is growing confidence that the front will bring easterly
gale force winds along the north gulf coast from Wednesday through
Thursday. During the same time frame, widespread high end
southerly gales with the potential of storm force gusts ahead of
the front will spread across the Gulf and along the Alaska
Peninsula. Seas building above 20 ft are expected as well. Winds
and seas will diminish by Thursday morning. Forecast confidence
with this storm system is moderate to high.

Bering Sea/Aleutians:

A well developed North Pacific low approaches near Sand Point
late Tuesday night into Wednesday morning. Expect north-
northwesterly gale force winds funneling through gaps and passes
along the Central and Eastern Aleutians/Alaska Peninsula through
Wednesday afternoon. Seas will build to 20 ft Pacific side of the
Central Aleutians and on the Bering side as well. As the center of
the low pushes out east into the Western Gulf, winds and seas
will subside by Wednesday evening.

Another North Pacific low will approach near the Central
Aleutians Thursday morning. There is a potential for another round
of gales and elevated seas extending across the same regions and
possibly in the Bering Sea for the rest of day Thursday. However,
there is model uncertainty with the overall track, position, and
strength associated with this storm system. Therefore, forecast
confidence is low.

&&

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

Overall, the latest operational model runs are in decent
agreement with the synoptic scale features in the short term, but
begin to diverge toward the end of the period. An active weather
pattern will be the main theme for the entire southern state as a
series of North Pacific lows will track north of the Western Gulf.
Compared to previous model runs, the first low approaches closer
to Kodiak Island instead going into the Southwest mainland for
late Tuesday night into Wednesday morning. Widespread moderate to
heavy precipitation and gusty winds are increasingly likely as
southerly flow draws warmer air in the Gulf. Most of the warmer
air will be confined along the north Gulf coast with a wintry mix
and/or all rain.

Meanwhile, an Arctic low over the western mainland will bring a
surge of colder air across the Bering Sea and Aleutian Islands.
This will help maintain the potential for snow for these regions,
in addition to the interior valleys and surrounding high
elevations as well. Subsequent lows will continue from Thursday
onward. However, model spread has increased significantly with the
track of these lows and interactions of small to mid scale
embedded systems streaming northward from the Southern Bering Sea.
For now, a wet and active pattern will likely persist as we head
into next week.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gales: 119, 120, 130, 131, 139, 352.
         Heavy Freezing Spray: 130, 179, 185, 412, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JPW
SOUTHCENTRAL ALASKA...CQ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...AS
MARINE/LONG TERM...MF