Alaska, 2023

Winter Weather in Alaska, December 9 to 11, 2023

December 9 to 11, 2023 · NWS AFC · 2 events in 2 counties and zones

The same winter storm which impacted the zones to the south and east of Anchorage would move into the Cook Inlet on the 10th of December causing widespread areas of blowing snow due to snowfall of 2-3 inches and winds which gusted to 50-60 mph overnight on 12/11 across the Anchorage Bowl and heavier snows across the Susitna Valley.

The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
2

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS AFC wrote it up.

The same winter storm which impacted the zones to the south and east of Anchorage would move into the Cook Inlet on the 10th of December causing widespread areas of blowing snow due to snowfall of 2-3 inches and winds which gusted to 50-60 mph overnight on 12/11 across the Anchorage Bowl and heavier snows across the Susitna Valley.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Anchorage, AK wrote its last area forecast discussion before the first event at Dec 9, 5:39 PM AKST, 2 hours 18 minutes earlier.

Area forecast discussion, Dec 9, 5:39 PM AKST, 2 hours 18 minutes before
Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
539 PM AKST Sat Dec 9 2023

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

Key Messages:

-Light snow moving over the Anchorage, Mat Valley & Prince William
 Sound will taper off later this evening with an additional 1-2"
 of accumulation possible.

-A strong low pressure system will move up from the North Pacific
 Sunday and move up towards the Cook Inlet Monday Morning. Strong
 winds, heavy snow and whiteout conditions are possible across the
 greater Prince William Sound and Kenai Peninsula Regions. Several
 inches to a few feet of snowfall will be possible for portions of
 these regions.

-Additional rounds of moderate to heavy precipitation are likely
 to continue into the remainder of the week as several additional
 low pressure systems ride up into Southcentral along a deep
 moisture axis streaming north into the coastline.

Discussion:

A negatively tilted upper trough is now moving up into the Kenai
Peninsula this evening. This is focusing synoptic lift that is
beginning to shift away from the Mat Valley and Anchorage area out
into the Chugach Mountains, as evidenced by a band of colder
cloud tops (around -50C on IR imagery) now extending between the
Prince William Sound and Talkeetnas. Light snow still lingering
over the Mat Valley and Anchorage Bowl should taper off over the
next few hours as the trough moves past, with perhaps an
additional 1-2" possible through late this evening. Light snow
will shift mostly towards eastern portions of the Chugach Range
overnight as a second narrow but extensive west-east oriented
trough overtakes the smaller shortwave as it lifts north into
Southcentral.

Attention on Sunday then turns back to the west as a deepening area
of low pressure over the North Pacific will move up near Kodiak
Island, bringing widespread gale force (>34kt) and areas of storm
force (>48 kt) winds to the Gulf of Alaska and Cook Inlet.
Widespread precipitation will spread from Kodiak Island up into the
Gulf Coast as a warm front lifts north throughout the day, bringing
an atmospheric river into the coastal mountains. Recent model trends
have the low center on a more westward trajectory up the Cook Inlet.
This regime is a bit more favorable for downsloping across portions
of the western Kenai northward through Anchorage and the Mat-Su
Valley. Even so, strong and gusty winds developing out of the
Matanuska Valley could lead to areas of blowing snow from Sunday
afternoon through Sunday night. Gusty north winds could also make
it down into the west side of Anchorage during the evening
tomorrow and lead to localized areas of blowing snow as well.

Meanwhile, heavy precipitation characterized by several feet of
snow is likely for the Kenai and Chugach Mountains. For the road
system, the heaviest snow is likely for Thompson Pass and Valdez,
as well as portions of the Seward Highway. An influx of warmer air
is likely to lead to rain/snow mix or rain for some coastal areas
such as Seward and Whittier by Monday. Winter Storm
Warnings/Advisories going into effect later on Sunday have now
been issued for areas covering the Kenai Peninsula and much of the
greater Prince William Sound & Chugach Range. Please see
information covered under the matching product for your location
for further details for timing/amounts of snow, winds and reduced
visibility.

While details remain uncertain, confidence is high the deep upper-
level trough will drive another 2-3 areas of low pressure into
southcentral Alaska through midweek. A near continuous stream of
moisture will result in near continuous snow (/low-level coastal
rain) for mountainous areas, with blizzard conditions possible in
susceptible areas such as Thompson Pass. A big forecasting challenge
with this series of systems will be the degree of 'inland'
(including western Kenai and Anchorage area) precipitation as times
of cross-barrier flow should subside, allowing precipitation to fill
back in across the area.

-Brown/AS

&&

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

A weakening low centered along the Southwest Coast is the main
focus of weather through tonight, as several weak shortwave
troughs rotate around a common center, producing mesoscale bands
of localized moderate snow showers. One particular trough tracking
into Bristol Bay this evening will move over Dillingham and into
interior Bristol Bay tonight, bringing the potential for a few
inches of snow there, while the rest of mainland Southwest Alaska
remains largely dry. Further west, cold air streaming south across
the Bering Sea is providing enough instability over the
relatively warm sea surface to produce persistent snow showers
along the Alaska Peninsula and the Aleutian Chain as far west as
Adak.

Attention shifts to an elongated low centered south of the
eastern Aleutians this evening, taking aim at Southwest Alaska
tonight, which has prompted the issuance of a Blizzard Warning
for Bristol Bay. Early Sunday morning, snow will begin to spread
across the Alaska Peninsula, combining with increasing winds to
produce the potential for blizzard conditions. The heaviest snow
shifts north toward Dillingham and interior Bristol Bay through
the morning hours, where winds will be strongest (gusting as high
as 45 mph), and conditions are most likely to be the worst. There
is a wide range of snowfall amounts forecast with this storm
system, ranging from 6 to 18 inches through Monday morning. The
main question that remains is where the heaviest snow will fall,
and thus where the longest duration of blizzard conditions will
occur. There is a range in model solutions which set up the band
of heaviest snow as far west as Dillingham north through
Koliganek, and as far east as east of King Salmon north through
Iliamna. Anywhere between, and including, either corridor may see
localized snow amounts in excess of 12 inches. The current
forecast depicts a middle ground solution between each extreme.

Further north in the Lower Kuskokwim Valley, 4 to 8 inches of snow
are possible, with winds gusting as high as 40 mph. As a result, a
Winter Weather Advisory has been issued from Sleetmute east,
including Stony River and Lime Village. There is lower confidence
in snow totals and winds affecting these communities coinciding in
visibility reductions to one half mile or less, but there is at
least moderate potential. Winds and snowfall intensity begin to
diminish Monday morning, which will decrease the threat of very
low visibilities.

For Monday and Tuesday, confidence decreases with how the low
continues to evolve, its track, and location of precipitation.
What most possible scenarios agree on is a broad low centered
somewhere over southern mainland Alaska, which will facilitate
continued strong northerly flow, likely to gale force over the
eastern Bering Sea, with gusty northerly winds affecting the
Kuskokwim Delta. Since there is some potential that lighter snow
spreads west into the Kuskokwim Delta on Monday, it is possible
that blowing snow may lead to low visibilities. Another area of
potential concern is the Alaska Peninsula and Aleutian Islands.
The broad low sitting over southern Alaska will cause a continued
stream of increasingly colder air to be drawn south between it
and high pressure in the western Bering Sea. This will lead to
persistent snow shower activity along the north side of the Alaska
Peninsula and along the Aleutian Chain as far west as Adak. With
decreasing air temperatures, shower activity may become more
vigorous and may lead to more significant reductions in
visibility as gusty winds continue to blow across the region.

CQ

&&

.LONG TERM FORECAST (Days 4 through 7)...Wednesday through Saturday...

The active weather pattern across southern Alaska, the Bering Sea,
and the Gulf of Alaska looks to continue through the long-term
period. The main weather-maker Wednesday through Friday will be an
upper-level low located in the vicinity of Bristol Bay/Alaska
Peninsula (AKPEN). This low looks to slowly move eastward into
the Gulf of Alaska through Friday and de-generate into an open
trough then. Numerous shortwaves will rotate around this
low/trough as it moves eastward. Coastal locations on the Bering
side of the AKPEN, as well as the Gulf coast and coastal
mountains look to receive the most precipitation in general.
Surface low tracks are uncertain at this time. There is reasonable
agreement that once this upper low/trough moves east, an upper
ridge will build in behind and provide a little reprieve from the
unsettled conditions Thursday for Southwest Alaska and Thursday
evening into Friday morning Southcentral and the Gulf. A new upper
low and associated trough enter the western Bering Thursday. A
strong low pressure pushes its front eastward across the Aleutians
Thursday and to the coast of Southwest by Friday. This front then
makes it across inland Southwest and begins to effect
Southcentral by Saturday. There is uncertainty in any snow amounts
due to exactly when the parent low pressure occludes and if a
secondary low pressure forms along the front. In general, marine
winds with the low pressure systems look to be in the small craft
to gale-force category around the Gulf, Bering, and North Pacific
side of the Aleutian Chain and AKPEN through Saturday.

&&

.AVIATION...

PANC...The upper level short-wave responsible for the ongoing
snowfall will pass through between 03Z and 06Z, leading to
improving ceiling/vis. Snow showers and MVFR conditions could
linger until around 12Z. After this point, surface winds will
shift around to northerly and begin to strengthen ahead of a
storm system near Kodiak Island. This leads to high confidence in
VFR conditions beginning sometime Sunday morning. There is
uncertainty in the track of the storm across the Gulf Sunday
through Sunday night. At this point, it looks like the terminal
will remain mostly dry due to easterly downslope flow. However,
there is a chance that snow and lower ceiling/vis develop sometime
Sunday afternoon or evening.

&&

Event by event

2 winter weather. Local standard time, as filed.

Winter Weather, Anchorage

When
December 9, 7:57 PM AKST to December 11, 3:31 AM AKST
Where
Anchorage forecast zone
Reported by
COOP Observer

Spotter report from Potter Valley of blowing snow and winds gusting to 60 mph (time based on nearby sensor gusts).

Winter Weather, Susitna Valley

When
December 10, 4:21 PM AKST to December 11, 9:00 PM AKST
Where
Susitna Valley forecast zone
Reported by
COOP Observer

New snowfall of 10.5 inches was reported at Trapper Creek, AK.

What these are

Winter Weather
Snow, sleet or freezing rain below warning levels that still caused disruption, damage or casualties.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Alaska in 2023Every state in 2023This day in weather historyWarnings in Alaska, December 2023

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1151728, 1151733.