Blizzard in Alaska, January 11 to 12, 2021

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
247 AM AKST Mon Jan 11 2021

.SYNOPSIS...
Another day, more flow from the south as the Pacific wave train
of lows continues to dominate the regional weather pattern. Yet
another low sits in the Gulf of Alaska with waves of energy
rotating inland across the Alaska Range, promoting a moderate
Tanana Valley Jet and bursts of Alaska Range gap winds. A
shortwave trough rotating around the larger low in the Gulf will
move inland today and tomorrow, bringing a reprieve in the
pattern with increased inland snow chances, including for
Fairbanks, today and moving northward tonight and Tuesday. Blowing
snow will continue to be a problem over the Bering Coast and will
become an issue along the North Slope heading into the new week.

&&

.DISCUSSION...

Upper Levels and Analysis...
A very large upper level low dominates the weather pattern, with
this 493 dam 500 hpa low centered over Chirikof Island just
southwest of Kodiak. The low pretty much encompasses the entire
Bering Sea, most of the North Pacific, and the Gulf of Alaska and
Mainland of Alaska. A shortwave trough is moving inland along the
Gulf Coast this morning, crossing the ALCAN into the Fortymile
Uplands. This feature will be a major weather player for the
Interior and North Slope today and through Tuesday. At the
surface, there is a 961 mb low centered directly under the upper
low, thus the low is vertically stacked and no longer baroclinic.
This broad cyclonic low level flow is directly supporting gale
force northerly winds through the Bering Strait with areas of
blowing and drifting snow for coastal areas. Fog and stratus
currently inhabit the North Slope as weak onshore flow is
redeveloping.

Model Discussion...
The numerical weather models are in very good synoptic scale
agreement, but they remain in relatively poor agreement with the
strength and track of a shortwave trough, effectively an "easterly
wave", which will move north through the Eastern Interior this
morning through tonight. However, the general trend, if you take
all the models and average them out, is for this shortwave trough
to be stronger as it moves north through the INterior. The one
lone model not to do this is oddly enough the GFS, which had been
the strongest solution for multiple runs in a row. The GFS now
takes this low northeast into the Yukon, which the ECMWF was doing
last night. Now the ECMWF tracks this feature across the Brooks
Range and North Slope through Tuesday night. The favored models
for this forecast will be the stronger solutions which bring snow
to pretty much all of the Central/Eastern Interior north of the
Tanana Valley with little to no snow south of it. Fairbanks will
be in the middle and we currently think any snow will be light and
less than one inch for Fairbanks proper.

Central and Eastern Interior...
A moderate Tanana Valley jet continues to blow all the way through
Delta Junction to Nenana. Nenana, at midnight, remains above 32
degrees! A shortwave trough will quickly track from the Fortymile
Uplands this morning and move through the Interior today and
tonight, bringing increasing snow chances as it moves through.
Pretty much all locations north of the Tanana Valley will
accumulate snow with anywhere from 1-3" possible, favoring higher
elevation terrain from the White mountains northward. Fairbanks
and the Tanana Valley will likely see flurries and light snow, but
the dry air in place and the continued easterly Tanana Valley Jet
will severely limit snow threats with generally less than an
inch. Real dry areas closer to the Alaska Range will see no snow.

This wave exits Tuesday as it tracks northwest, with a brief
reprieve in the Tanana Valley Jet. However, this will be short-
lived as more southerly flow aloft moves over bringing southerly
AK Range gap winds and a light-moderate Tanana Valley Jet. Back to
more dry weather with a brief return to closer to normal temps for
the Interior.

West Coast and Western Interior...
Strong northerly winds to gale force over the coast will continue
through late tonight before they gradually begin to drop off
Tuesday. The region will come under the influence of a more
easterly flow direction aloft with increasing threats for light
snow beginning over the Western Interior late today with the band
of snow moving toward the coast Tuesday. Expect light snow amounts
favoring locations north of the Lower Yukon Valley. Snow exits
Wednesday morning with some lingering snow showers over the YK
Delta and Yukon Valley. Otherwise, the weather will be quiet and
mostly low impact for the latter half of the week.

North Slope and Brooks Range...
Fog and stratus are the current dominate mode this morning.
However, the pattern shifts as an easterly gradient tightens up as
a low over the Interior moves north and a high over the Arctic
moves south. The low will also bring light snow to the region, and
with easterly winds increasing to 25-45 mph, expect widespread
areas of blowing and drifting snow with reduced visibility,
especially along the immediate Arctic Coast. Gusts to 45 mph are
likely by Tuesday over exposed capes. Blustery east winds and
blowing snow end over the Eastern Arctic on Wednesday night and
Thursday as the strong gradients relaxes, although it will remain
blustery over the Western Arctic.

Extended Forecast Days 4-7...
Beginning the extended period forecast on Thursday, there will be
a strong cyclone moving north through the Gulf of Alaska with a
broad high pressure ridge extending all the way through the
Chukchi Sea. Broad southerly flow will be the name of the game,
but this pattern looks like it will be a little more active as a
series of lows from the Pacific and Bering eventually begin to
make inland progress, keeping threats for periodic light snow in
place over the Mainland. Temps will remain seasonal if not
slightly above average as the southerly flow aloft will keep a
gradient up along the AK Range with southerly winds through the
gaps and a Tanana Valley Jet from the east.

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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Winter Weather Advisory for AKZ202-AKZ203-AKZ213.

Gale Warning for PKZ210-PKZ220-PKZ240.

Brisk Wind Advisory for PKZ200-PKZ225-PKZ230-PKZ235-PKZ245.

&&

AHSENMACHER JAN 21