Winter Storm Warning 37, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
342 PM AKST Mon Dec 21 2020

.SYNOPSIS...
A strong winter storm is moving into the YK Delta and Saint
Lawrence Island this afternoon. The front will move north tonight
supporting strong easterly winds and dangerous winter weather
conditions as it tracks along the coast. Along the North Slope,
bitterly cold air is in place. Over the Interior, pretty quiet
weather, but with strong southerly winds developing across the AK
Range, gap winds will rapidly ramp up along with an increasing
Tanana Valley Jet. Temps will warm to well above average in
response tomorrow and Wednesday.

&&

.DISCUSSION...

Upper Levels and Analysis...
The upper level pattern is rapidly amplifying as a strong 947 hpa
low exists over the Bering Sea with the associated warm front
lifting north across the West Coast. Approx 500 dam heights at 500
hpa remain over the North Slope, and this is where the coldest air
exists with 850 hpa temps around -25C. Very strong easterly
offshore winds are already ramping up over the YK Delta and Saint
Lawrence Island where blizzard conditions are already occurring.
The warm front moving up along the coast is tapping around 30N
latitude, so there is quite a bit of energy associated with this
low.

Model Discussion...
The numerical weather models are in very good agreement overall,
and much better agreement than the preceding 3-4 days. The biggest
discrepancy is on Tuesday night and Wednesday as a strong Gulf of
AK low moves north across the AK Range with each model completely
different on timing and strength, which would impact winds in the
Interior as well as how warm temps get. For now a blend was
favored, with a favoring of the Canadian model along the North
Slope where it has been dominating with the easterly wind regime,
and over the Interior, a blend to the NAM and GFS. Temp forecast
was also accordingly increased for Tue and Wed for the Interior.

Central and Eastern Interior...
The gradual warmup/Chinook pattern begins tonight as clouds roll
in and warmer air aloft increases. The pressure gradient across
the AK Range will tighten in response so there will be an equally
quick uptick in gap winds and also the Tanana Valley Jet. High
wind warnings remain in effect for the AK Range gaps while a wind
advisory remains in effect for the Tanana Valley jet to 60 mph.
Tuesday night into Wednesday the main surface low crosses the AK
Range and "ejects" into the Interior, and this will bring
increasing chances for a wintry mix of precipitation to the
Interior. The cold front pushes through Wednesday and Wednesday
night, bringing a shot of snow to the whole Interior. Takeaway,
with warming temps and these chances for mixed precip, expect some
possibly tricky travel Tuesday through Wednesday.

West Coast and Western Interior...
The front from the Bering Sea is moving north across the YK Delta
and Saint Lawrence Island as I type this, and it will continue
north through tonight, bringing widespread areas of snow and
blowing snow, with localized blizzard conditions in the normal
blowholes for easterly offshore winds which will reach 55-65 mph
in select locations. Snow will mostly be heaviest over the Nulato
Hills and other elevated terrain given the nature of this
occluded front, with the heaviest snow totals otherwise being over
the Bering Coast including the southern portion of the Seward
Peninsula. The strong surface low weakens tomorrow night, bringing
an end to the blizzard conditions. Snow also ends Tuesday night,
with the next low bringing more snow to the region Wednesday
through Thursday, although this low will not have the strong
easterly offshore winds and blizzard conditions.

North Slope and Brooks Range...
Bitterly cold temps and wind chills (currently 40 to 60 below)
will gradually lessen as warm air advection aloft slowly warms
temps. However, this will re- tighten the gradient right back up
with increasing easterly winds and more chances for significant
blowing and drifting snow along the whole North Slope. Like the
past couple weeks, the strongest winds and worst conditions will
be over the Western Arctic where winds will push into the 35-50
mph range from the east, with lower values over the Eastern
Arctic. Expect areas of significant blowing and drifting snow,
possibly getting close to blizzard conditions over the Western
Arctic tomorrow and tomorrow night.

Light snow threats move into the region Wednesday night and
Thursday, along with increasing southerly gap winds which will
also bring some blowing snow to Atigun Pass and the other gaps in
the Brooks Range.

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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Blizzard Warning for AKZ213-AKZ214.

High Wind Warning for AKZ225-AKZ226-AKZ227.

Wind Advisory for AKZ223.

Wind Chill Advisory for AKZ202-AKZ203-AKZ204-AKZ206-AKZ217.

Winter Weather Advisory for AKZ201-AKZ216.

Winter Storm Warning for AKZ207-AKZ209-AKZ210-AKZ211-AKZ212-
AKZ215.

Heavy Freezing Spray Warning for PKZ210.

Gale Warning for PKZ200-PKZ210-PKZ215-PKZ220-PKZ225-PKZ230.

Brisk Wind Advisory for PKZ235-PKZ240-PKZ245.

&&

AHSENMACHER DEC 20