Gale Warning 138, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
446 PM AKST Fri Feb 10 2023

.ANALYSIS AND UPPER LEVELS...

A strong low is situated over the Alaska Peninsula this afternoon
with its front extended from Bristol Bay and over Cook Inlet and
the north Gulf coast. This front is bringing snowfall to Southwest
Alaska and has induced the strong northeasterly winds in the
Kuskokwim Delta bringing in the Blizzard conditions. Snow and
blowing snow is also occurring around the north Gulf coast areas
with this front.

The jet stream is zonal off Asia and then turns more to the
northeast well south of Adak and then weakens just south of the
Gulf of Alaska. The jet stream trajectory will move eastward and
this will start to remove the upper level support from the AK
Peninsula low and the other surface low that can be seen south of
Adak on satellite.

&&

.MODEL DISCUSSION...

Models remain in good synoptic agreement into early next week. The
biggest question with the models still revolves around the way a
triple point low moves into the northern Gulf and Cook Inlet area
Saturday into early Sunday. Confidence is also increasing with
the track and overall strength with the strong lows next week
moving along the Aleutians and Bering Sea.

&&

.AVIATION...

PANC...VFR conditions should prevail through Saturday. There is a
chance for some light snow to bring MVFR conditions late Saturday
afternoon, but confidence is low in the track of weak upper level
short-waves lifting northward across the region.

&&

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

An active weather pattern continues across Southcentral Alaska
for the next few days as a series of lows move through the area.
Widespread gale and storm force winds along the coastal waters of
the northern Gulf will ease this evening and tonight. Strong
downslope forcing will remain in place across the Anchorage Bowl
and thus result in minimal precipitation with this first system.
The next low will then move in Saturday night into Sunday morning.
Downslope forcing is expected to be weaker with this next low
which means the chance for snow will be greater in Anchorage than
compared to this first low. Strong cold air advection is expected
in the wake of this second low on Monday. This strong cold air
advection will result in widespread storm force winds with
hurricane force gusts likely in the bays and passes. Heavy
freezing spray is also likely across the western Gulf on Monday
as a result of the strong winds combined with cold temperatures.

&&

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

Blowing snow and stronger winds earlier causing near whiteout
conditions along coastal areas between Dillingham and Kipnuk is
beginning to subside as the wind field around the low now moving
up the Alaska Peninsula weakens on approach to Bristol Bay.
Falling snow will persist for quite a bit longer into Saturday
across parts of Bristol Bay and most of the Lower Kuskokwim Valley
as the remnant low opens up into a trough and lifts northeast
around a nearly stationary upper level low drifting near St
Lawrence Island. Lingering light snowfall will slowly clear from
southwest to northeast through Sunday night as the main upper low
continues to drift north and as frigidly cold Arctic air blasts
into the region from the northern Bering. Frigidly cold temperatures
will return as skies begin to clear early on Monday while Arctic
air remains in place at the surface, with widespread lows early
Monday dropping into the -10s to -20s. Some rebound in temperatures
will begin by Monday night as the next strong frontal system on
the horizon approaches the Southwest coast.

&&

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

Conditions are finally beginning to improve across most of the
region as the storm force low weakens to gale force over the
eastern Bering Sea. Northerly winds at or below small craft
intensity will continue for much of the day on Saturday as Arctic
air spills south into the Pribilof Islands and Aleutian Chain
from the northern Bering. Winds will pick back up to gale force
through gaps and passes along portions of the Alaska Peninsula on
Sunday as the surge of cold air couples with favorable upper level
support, with storm force gusts also possible near the peak of
gap wind intensity. Meanwhile, widespread freezing spray will
continue farther north due to the combination of gusty northerly
flow and cold air temperatures, with extreme freezing spray rates
expected along the ice edge through Sunday.

By Sunday evening, yet another very intense North Pacific low will
approach the western Aleutians from the southwest. Storm force
sustained winds will pick up from the northeast ahead of the low's
front, with gusts in Hurricane force range likely somewhere
between Adak and Shemya, depending on exactly where the corridor
of strongest winds develops and on the the exact low track. There
is a good chance precipitation ahead of the front/low will start
out as snow on Sunday evening due to the initially very cold
Arctic air in place ahead of this system. This could result in a
period of blowing snow and reduced visibility before warmer air
moves in and changes falling precipitation over to rain, depending
on whether surface temperatures are able to remain at or below
freezing as snow begins. The low will approach Atka as it starts
to weaken on Monday, with the front most likely remaining at or
near storm force as it progresses into the eastern Aleutians and
Pribilofs. Widespread snow and blowing snow will again be possible
across the Pribilofs as the front approaches Monday into Monday
evening.

&&

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

A highly amplified pattern is expected next week with a series
of strong lows forecast to track across the region. Forecast
confidence remains above average as models continue to be
relatively consistent with the depiction of several strong
synoptic features. Tuesday morning, a weakening low centered near
the eastern Aleutians may bring a period of storm-force gusts
through the islands and to the Alaska Peninsula through early
Wednesday. Strong cold advection on the back side of the low will
help to mix down strong winds aloft and support snow showers and
periods of low visibility conditions as the low tracks east. Model
solutions appear slightly north of where they were yesterday and
in greater agreement with regards to the track of the low. This
would take it along a similar track to the low centered near the
southern tip of the Alaska Peninsula this evening. Precipitation
spreads into southern mainland Alaska on Tuesday as the low pushes
its front northward. The air mass out ahead of the low should be
sufficient to keep all precipitation snow for inland locations.
Along portions of the north Gulf coast, rain may be possible at
low elevations, especially on the east side of a weak triple point
low that looks to develop in the northern Gulf. Precipitation
gradually tapers off going into Wednesday as the main source of
moisture is shunted eastward and the broader upper-level trough
begins to lift out of the area.

Out west, a low near Kamchatka, potentially as deep as 940 mb,
pushes a storm force front into the western Aleutians on Tuesday.
Along with it comes a southerly push of warmer air, which should
quickly switch precipitation from snow to rain. The front sweeps
to the eastern Aleutians by Wednesday, but uncertainty grows
thereafter. Models begin to disagree on whether the front stalls
out or is able to push into Southwest Alaska Wednesday night. Both
GFS and EC favor an eastward progression, and if it materializes,
the warm air moving in over cold air at the surface may be
sufficient to produce a period of freezing rain along the Bristol
Bay coast, while the rest of the area would see snow. Both models
keep the front progressing into Southcentral, where it has the
potential to bring several inches of snow on Thursday, but this
is lower confidence. Various shortwaves rapidly lift out ahead of
the deep low as it decays over the western Bering Sea on Thursday
and Friday. While there is significant uncertainty with the
placement of these features, models are in rough agreement on
the potential for a second, weaker front to sweep across the
central/eastern Aleutians/Bering Sea to the southern mainland,
bring mostly snow, with low potential for rain/mixed precipitation
near the coast. Though timing and placement is uncertain, Southwest
Alaska is the most likely area for this front to bring precipitation,
with lower confidence of moving on into Southcentral for the weekend.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory 125 131.
MARINE...Heavy Freezing Spray Warning 160 165 179 180 185.
         Storm Warning 119.
         Gale Warning 125 130 132 139 150 155 178 181.
FIRE WEATHER...NONE.

&&

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