Heavy Snow in Alaska, September 20 to 22, 2021

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
450 AM AKDT Mon Sep 20 2021

.SYNOPSIS...
Cold, rainy September day? How about snow instead. An early season
winter storm will impact the far Eastern Interior and Eastern AK
Range through the next couple days. Snow squalls will continue
over the North Slope and NW Arctic Coast. Rain/snow will push
across the Tanana Valley today as the front tracks through, with
lighter snow accumulations possible. Winter storm warnings will be
in effect for the Interior from Delta Junction east.

&&

.DISCUSSION...

Upper Levels and Analysis...
A rather seasonably strong 507 dam 500 hpa arctic low is centered
directly over Point Barrow this morning, which can be clearly seen
on satellite as a tight, wrapped up cold occlusion. The cold front
stretches from Lake Minchumina to Arctic Village. A low in the
Gulf of Alaska is moving northeast this morning, and this will
continue north bringing the heavier snow tonight and Tuesday.

Model Discussion...
All models are doing fairly well with the synoptic scale pattern,
and they are all now closing the low off over the Gulf of Alaska
Tuesday, which should keep it snowing toward the ALCAN through
Wednesday morning, possibly Wednesday afternoon. A low sneaking
across Saint Lawrence Island and into the YK Delta on Tuesday is
being handled worse by the models, with a seeming trend farther
south from today, so we favored a 06Z NAM blend to shift it south,
mainly only impacting the Delta and Saint Lawrence. Otherwise, the
only other difference is a slowing of the front as it crosses
Fairbanks, so we decided to slightly increase the snow amounts
possible this morning.

Central and Eastern Interior...
The front is making southeast progress and will bring rain/snow
turning to snow as it moves through Fairbanks and towards the AK
Range. Still expecting 2-4" for the Parks south of Nenana and
possibly 5" for the Denali Park Rd. Fairbanks will see possibly
around 0.5-1" slush, with 1-3" up in the Hills and farther south
toward Salcha. The front stalls over Delta Junction and east
tomorrow as a Gulf low shifts north, bringing more snow as it
clears out to the west. Winter storm warnings will be in effect
for the Eastern AK Range, AK highway, and Taylor Hwy corridors for
4-8" of snow, with higher amounts in Isabel Pass along the
Richardson to 6-11". Strong north winds to 50 mph will also blast
through the southern corridor of Isabel Pass, but snow will also
be somewhat lighter there, so there will be some blowing snow, but
not expecting major blowing snow/drifting snow.

Most snow ends on Wednesday and it clears out with lingering snow
moving north along the ALCAN up towards the Eastern Brooks Range.
For the first storm of the season, this looks like a pretty
"good" one.

West Coast and Western Interior...
Strong northwest winds will continue into Tuesday before gradually
diminishing and shifting to a lighter north direction. Rough surf
will also diminish. Rain/snow squalls off the open waters will
also continue through that time period then diminish Tue night and
Wednesday. A low will cross the N Bering Sea directly over Saint
Lawrence then over the YK Delta Tue, bringing rain and north winds
as it moves inland through Tue night. Some accumulating snow is
possible along the north side of this low across the Yukon Delta.
The Interior is pretty dry over this period, with cold inversions
at night.

North Slope and Brooks Range...
A strong low center near Point Barrow will shift east along the
Arctic Coast, bringing widespread snow squalls, possibly mixed
with a little rain at times. Strong northwest to west winds will
keep rough surf over the west Arctic through tonight with a
gradual downtrend thereafter. Expected continued snow showers
along the Dalton highway, but nothing more than a couple inches.
The gradient really tapers off Tue night with a reduction in snow
showers, as well.

Extended Forecast Days 4-7...
A cold arctic high will be in place over the Mainland with another
low moving into the Gulf of Alaska on Thursday. Expect Interior
temps to be rather cool for Interior valleys at night. There is a
lot of uncertainty for Friday as there is still a chance for
another snow event for the Interior Friday and Saturday, but the
track of the gulf low as it lifts north is highly uncertain among
the three major global models. However, the chance is still higher
than normal for more snow during time frame, so stay tuned.

Coastal Hazard Potential Days 3 and 4...None.

&&

.HYDROLOGY...
None.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Winter Storm Warning for AKZ223-AKZ224-AKZ226.

Winter Weather Advisory for AKZ225.

Small Craft Advisory for PKZ215-PKZ220-PKZ225-PKZ230-PKZ235-
PKZ240-PKZ245.

&&

AHSENMACHER SEP 21