Blizzard in Alaska, December 15 to 17, 2021

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
419 PM AKST Tue Dec 14 2021

.SYNOPSIS...
A very cold airmass over Northern Alaska will transition to warmer
and snowy over the next several days. The West Coast will have
strong winds and blizzard or near blizzard conditions developing
late tonight or Wed with temperatures warming to near normal.
The snow and warmer conditions will move into the Western
Interior Wednesday night and Thursday, and into the Eastern
Interior on Thursday. Expect 3-6 inches of snow over the West
Coast through Thu, with 2-4 inches over the Western Interior Wed
night through Thu night, and 1-2 inches over the Eastern Interior
Thursday night through Friday. This storm will also cause
increased east winds across the West Coast and North Slope
tonight with cold winds chills. The North Slope will see low
visibility in blowing snow starting Wed evening. The Interior
will see increased east winds and cold wind chills over typical
east winds drainages of the Interior on Wed PM.

A second storm will move over SW AK Friday will bring another
round of snow and blowing snow to the West Coast and SW AK on Fri.

A third and much stronger storm will bring heavy snow and
blizzard conditions to the West Coast and Western Interior Sat
night through Mon AM, with mixed precipitation or freezing rain
south east of Nome to McGrath on Sun. This will also bring strong
SW Gale force winds across the Bering Sea giving a possibility of
Coastal Flooding to the West Coast of Alaska Sun into Mon. This
storm is expected to bring heavy snow into the Central and Eastern
Interior Sun into Mon or Tue. Could see 1 ft or more of snow
across most of Northern Alaska from the Brooks Range south Sun
into Mon.

Aloft...
The long wave pattern consists of a trough stretching from the
North Pole south over Alaska into the eastern Gulf of Alaska, a
ridge over the eastern Bering Sea and West Coast of Alaska, and a
second trough over the NW Pacific and Western Bering Sea. This
pattern is becoming progressive as a series of strong short wave
troughs make their way east. The ridge will move east over
Mainland AK by Wed, then flatten slightly Thu as a strong short
wave troughs makes its way inland. After that time, southwest flow
aloft will bring a series of strong short waves trough inland
over Northern AK over the weekend.

This means that Interior AK will stay very cold into Wed, then
warm from west to east Wed night and Thu as clouds and snow spread
east. The strong short wave will bring significant snow to West
Coast AK Tue nigh through Wed night, and into the Western Interior
Wed night and Thu, before moving over the Ern Interior Thu.

It also means that Northern Alaska will have the potential
for heavy snow from the Brooks Range south for Sat night through
Mon or Tue, blizzard conditions over the West Coast Sat night
through Mon, and even mixed or freezing precipitation along the
West Coast and Southwest Interior Sat night through Sun.

A weak low aloft over the NE INterior will linger tonight, then
move east Wed. FLurries and clouds associated with this will keep
the NE Interior less cold Wed AM.

Surface...
An inverted trough from the Eastern Gulf of Alaska to the SE
Interior will move east late tonight. This is causing light snow
over the SE INterior which will taper of by Wed AM. Could see 1
inch of snow, and this will keep the SE Interior less cold.

A strong low in the Western Bering Sea will move to the Central
Bering Sea as a 974 mb low by 3pm Wed, then to 100 NM west of
Gambell as a 989 mb low by 3pm Thu, and to the southern Chukchi
Sea as a 100 MB low by 3pm Fri. An occluded front with this
features stretches east across the central Bering Sea. This front
will move to Anadyr to St Matthew Island to St Paul Is by 3am Wed,
to The Bering Strait to Nunivak Is by 3PM Wed, to the Chukchi Sea
to the Bering Strait to the YK Delta by 3am Thu, to Point Lay to
McGrath by 3pm Thu, to Utqiagvik to Anaktuvuk to Denali by 3am
Fri, and to the ALCAN Border by 3pm Fri. Heavy snow and SE winds
of 50 kt accompany the front to St Lawrence Is tonight, with the
snow decreasing to moderate amounts and winds dropping to gales
Wed as the front approaches the West Coast, and then winds
dropping to 25-35 kt as the front moves along the coast Wed night,
and to 15-25 kt Thu as the front moves inland. Expect 3-6 inches
of snow over the West Coast through Thu, with 2-4 inches over the
Western Interior Wed through Thu night, and 1-2 inches over the
Eastern Interior Thursday through Friday.

A trailing low will move into the southern Bering Sea on Thu, and
to the Eastern Bering Sea as as 985 mb low Fri. This will bring
4-6 inches of snow and blowing snow to the Wes Coast south of the
Bering Strait Fri.

A third and much strong low will move into the Western Bering Sea
on Sat, to the Southern Chukchi Sea on Sun, and to north of
Utqiagvik on Sun. See details in synopsis above.

&&

.DISCUSSION...
Models verify well aloft at 12Z, and show similar solutions
through 3pm Thu. After that time ,models differ on speed and
strength of incoming short waves, with the NAM bring faster than
all the other models. All models agree on a moist southwest flow
pattern over a round topped long wave ridge developing on the
weekend between Sat night and Tue AM over Northern Alaska bringing
above normal temperatures and the potential for heavy snow from
the Brooks Range south, with mixed or freezing precipitation over
SW AK on Sun. Models all show the long wave ridge building sharply
over AK next Tue-Wed to bring a return to clearing and colder
weather.

With precipitation, the ECMF is a bit faster than the NAM and GFS
bringing precip east into tonight through Thu. Favor better
agreement between the GFS and NAM with the slower advance of
precip tonight through Thu.

At the surface at 18Z, models verified a few mb too weak on the
high over the North Slope, as few mb too weak on the low over
Circle City, and 3-5mb too weak on the low in the Northern Gulf
of AK. This will cause west winds over the Eastern Arctic Coast to
be 5 kt stronger than models indicate there through tonight. This
will also likely cause north winds through AK Range Passes to be
3-5 kt stronger than models indicate through tonight. The deeper low
in the NE Interior may cause flurries to linger there into Wed.
Models show similar solutions on the large scale features
impacting the West Coast through Thu, with the NAM moving a
surface low across the Bering into SW AK Thu night and Fri much
faster than the GFS or ECMF. For winds will favor a blend of the
NAM and GFS through Thu, then use the GFS Thu night and Fri.

Bottom line for models is we will use a blend of the NAM and GFS
for temps, precip location and amounts through Thu, then use just the
GFS Thu night and Fri, but will linger flurries over NE AK into
Wed and light snow over the SE Interior in Wed AM. At the surface
will use a blend of the NAM and GFS through Thu, then just the GFS
for Thu night and Fri, but will bump up winds 5 kt of the Ern
Arctic Coast through tonight, and bump up AK Range Passes 3-5 kt
through tonight.

Coastal Hazard Potential Days 3 and 4...
Southwest gale force winds across the Bering Sea this weekend will
bring possibility of Coastal Flooding to the West Coast of Alaska
Sun into Mon.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory for AKZ223-AKZ224.

Dense Fog Advisory for AKZ222.

Blizzard Warning for AKZ213.

Wind Chill Warning for AKZ201.

Winter Weather Advisory for AKZ202-AKZ203-AKZ204-AKZ206-AKZ207-
AKZ208-AKZ209-AKZ210-AKZ211-AKZ212-AKZ214-AKZ215-AKZ217.

Gale Warning for PKZ200-PKZ215-PKZ220.

Storm Warning for PKZ210.

Brisk Wind Advisory for PKZ225-PKZ230.
&&

JB DEC 21