Gale Warning 159, NWS Anchorage, AK

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
550 AM AKST Tue Feb 8 2022

.ANALYSIS AND UPPER LEVELS...

A southwesterly 300mb jet stretches across the Gulf and is
exiting into Canada. An associated surface low is located north of
the Barren Islands and is tracking up Cook Inlet. The front
extending from this low has started to move inland and is
producing mainly snow along the coast and some areas of the Interior.
However, some coastal locations have reported periods of rain due
to low-level warm, southerly winds.

Out west, a deep upper level trough centered over the Y-K Delta
continues to drive very cold Arctic air southward across the
region. Aniak Airport reported wind chills dropping to as low as
-54F yesterday morning, and Bethel reported prolonged periods of
 wind chills colder than -40F yesterday morning through early
 this morning. Although temperatures will remain cold, the Wind
 Chill Advisory for the Kuskokwim Delta has been cancelled as
 winds have decreased across the area. Cloud streets visible on
 satellite have spread across the entire Bering Sea as very cold
 air streams southward off of the sea ice. As a result, convective
 snow showers continue over the Pribilofs and much of the
 Aleutian Chain.

&&

.MODEL DISCUSSION...

Although the models have come into better agreement regarding the
low moving into the Gulf on Wednesday, there is still uncertainty
with the speed of the low. With the current runs, the GFS and
Canadian are the slowest models. Nonetheless, all models indicate
a more eastward track compared to the previous runs. Despite the
current model uncertainty with this system, precipitation is
still expected to overspread the Gulf coast and southwest flow up
the inlet should create potential snowfall for Anchorage and the
Mat-Su. Another low pressure system will approach the Aleutians
from the North Pacific on Thursday. Significant differences are
present with this system as models are struggling with the timing
and track of the low.

Overall, forecast confidence remains high for active weather to
continue through the week, but confidence is still lower in
regards to the speed of the system Wednesday and the speed/track
of the system Thursday.

&&

.AVIATION...

PANC...VFR conditions are expected to persist through late
morning until light snow and associated IFR conditions develop.
Conditions will improve to MVFR/VFR in the afternoon as a low
pressure system moves inland and snow diminishes. Light northerly
winds will give way to gusty southerly winds briefly this
afternoon.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3/Today
through Thursday night)...

A surface low over the Kenai Peninsula will track by Anchorage
this morning, then dissipate as it moves inland. Strong easterly
flow ahead of the low center continues to produce downslope drying
for much of the western Kenai Peninsula, Anchorage, and the Mat
Valley. As the low progresses northward, winds will shift around
to southerly (bringing an end to the downslope flow) and the snow
will quickly fill in during the morning hours. A shallow layer of
above freezing air continues to advect northward east of the low
center, leading to a transition from snow to rain along many of
the Prince William Sound coastal communities. Also expect some
gusty winds in the central to southern Copper River Basin to mix
down some above freezing air this afternoon. However, as the low
heads inland Arctic air will quickly advect from southwest to
northeast across all of Southcentral, leading to a change back to
snow before precipitation ends. The upper level short-wave
providing a lot of the forcing for precipitation will track
quickly northward, exiting to Interior Alaska late this afternoon.
As a result, snow accumulation will generally be light, with the
exception of coastal mountains and the Susitna Valley, where the
southerly upslope flow will lead to heavier snowfall.

As one storm winds down over Southcentral late today, a new storm
will track out of the north-central Pacific and toward Kodiak
Island and the Gulf. There has been quite a bit of uncertainty in
the track of this low, but confidence has greatly increased in a
track east of Kodiak Island and up to Prince William Sound. Based
on this track some key adjustments were made to the latest
forecast to cool temperatures and increase snow accumulation for
all areas west of the low track. The further east track also means
the heaviest precipitation will be over eastern Prince William
Sound. Precipitation totals over the eastern Kenai Peninsula have
been lowered due to less favorable low level flow and not as much
upper level forcing.

Expect precipitation to spread to Kodiak Island by early this
evening, then to all of Southcentral later tonight. With a strong
southerly jet aloft, this storm will rapidly cross the region,
with the heaviest and steadiest precipitation diminishing from
southwest to northeast Wednesday afternoon and evening. The deep
and cold upper level low sitting along the western Alaska coast
will take an eastward jog Wednesday, leading to strong cold air
advection across Southcentral. This is often a good set-up for
heavy snow and significant snow accumulation. However, in this
case there is no significant upper level trough to accompany the
cold air. Instead, there are some weak short-waves embedded
within the cyclonic flow aloft. Thus, generally expect light snow
accumulation on the back side of the storm system Wednesday
afternoon through Thursday. With deep layer south to southwest
flow, the south to west side of mountain ranges will be favored
for snowfall and accumulation during this time period.

Yet another storm will track out of the Pacific Thursday, with
another round of precipitation likely reaching Southcentral
Thursday night.

&&

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

Cold Arctic air will remain over the Northern Bering through at
least Wednesday night. The deep, upper low associated with this
airmass will begin to move east overnight Wednesday into Thursday,
moving the coldest temperatures inland. Temperatures will
continue to be unseasonably cold across the entire southwest
through Thursday. Come Thursday afternoon, temperatures will
moderate before trending warmer again later in the week.

Snow will continue to fall through the morning and should end
near Iliamna later this morning and by noon in the Kuskokwim
Valley. A series of snowfall chances are expected this week. The
next quick moving low in the western Gulf, may produce a brief
wave of light snow with little to accumulation for the same areas
after midnight into Wednesday morning. With the motion of the cold
upper low eastward on Thursday, a shortwave may kick off another
burst of snowfall across the southwest as it moves towards the
Gulf. At this time, it appears to be a scenario of higher chances
of occurrence at some point but with little to no accumulation. On
the heels of this, a bigger system from the North Pacific may
push through later on Thursday evening but the details are more
uncertain.

&&

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

The stalled Arctic airmass and cold, upper level low in the
Northern Bering will keep temperatures unseasonable cold for the
Bering and Aleutians through midweek. The last time St Paul Island
was this cold was in 2017. Temperatures will slowly rebound for
the Aleutians once the upper low starts make some movement
eastward on Thursday morning. Widespread heavy freezing spray
remains a threat across the Bering, the Pribilofs, and the Alaska
Peninsula.

Satellite imagery showed cloud streets stretching from the ice
edge towards the Aleutians as northerly winds stream distributing
the cold air. Widespread, convective snow showers will continue as
a result through late Wednesday, when the low moves east and a
North Pacific low attempts to nudge into the Aleutians.
Precipitation chances will increase Thursday for the Central and
Eastern Aleutians. Enough warm air may advect into the area for
rain and snow to mix, but confidence is low with the exact set up
of this trough. Gale force winds are likely as portions of the
elongated cluster of lows approach the Aleutians Thursday.

&&

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

Gulf of Alaska:

As a Gulf low moves inland Thursday morning, winds will briefly
subside below small craft. Widespread small crafts with areas of
gales are expected along a front as it tracks across the Gulf
Thursday afternoon through Friday afternoon. Once the front moves
inland, winds will decrease to mostly below small crafts through
Saturday. Waves 20 ft and higher Thursday morning will diminish to
8-12 ft for the remainder of the period.

Bering Sea/Aleutians:

Uncertainty persists with the strength and track of an incoming
North Pacific low. Beginning Thursday morning, small crafts are
expected across most of the Bering as the low and its front push
northward. Gales are likely, with current guidance suggesting they
will extend across the Southern Bering and around the Central and
Eastern Aleutians. By Friday afternoon, winds are expected to diminish
to small crafts and lower. Another North Pacific low approaches
the region Saturday evening. Overall, waves will be mostly 8-12
ft, with seas peaking around 20 ft where gales are expected. As
winds stay mostly northeasterly through the period, cold air
advection and freezing spray will likely continue to be concerns.

&&

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

Models are continuing to indicate an active and wet period for the
North Pacific with the persistence of a longwave trough over the
Bering and the Northwest Pacific. Models are showing three
distinct lows for this forecast period, with the third low
potentially being the strongest of the bunch. However, there
continues to be substantial divergence with the tracks and the
intensities of these lows. The expected tracks seem to be staying
south of the Aleutian Chain and then making their way into the
Gulf towards Kodiak Island and then towards Prince William Sound.
Overall, expect an active weather pattern for the entire southern
state as a series of North Pacific lows dominate the region.
Additionally, models are showing persistence with a brutally cold
air mass being pulled south over the northern Bering and over most
of the state. However, these North Pacific lows will bring
relatively warmer air with them as they pull warmer air from the
south ahead of them, and then pull colder air from the north
behind them. Places like Prince William Sound and the coastal
areas could see rain and snow, whereas, the Southwest will likely
stay snow. As each low makes its way to Prince William Sound, the
cyclonic wrap-around of the low will likely cause upslope snow to
form and therefore, likely spill into the Southwest with each
passing low.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...Gale Warning: 119, 120, 125, 130-132, 138-141, 150, 155,
                       165, 185, 351, 352.
         Heavy Freezing Spray: 130, 138, 139, 141, 150, 155, 165, 179,
                       185, 412, 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AF
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...VR
MARINE/LONG TERM...KC/NS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
219 PM AKST TUE FEB 8 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1200 PM     SNOW             VALDEZ                  61.13N 146.37W
02/08/2022  E30.0 INCH       VALDEZ-CORDOVA     AK   PUBLIC

            SPOTTER REPORTED TWO FEET OF SNOW ON HIS
            ROOF AND 3 FEET OF SNOW ON HIS DRIVEWAY
            THROUGH 5 AM THIS MORNING. SPOTTER THEN
            REPORTED ANOTHER 6 TO 8 INCHES THROUGH
            AROUND 11 AM THIS MORNING.

&&

MV