Blizzard in Alaska, November 25, 2020

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
436 AM AKST Wed Nov 25 2020

.SYNOPSIS...
A powerful storm along the West Coast continues to unleash its
wrath on the West Coast as the powerful 948 mb low moves into the
Gulf of Anadyr. This is a surface pressure more closely
associated with mid range hurricanes than lows at this latitude.
Heavy snow, localized blizzard conditions, and storm force winds
are accompanying this storm, with a change to rain across parts of
the Yukon Valley and Bering coast. The pressure gradient is
tightening along the North Slope as well as areas of blowing and
drifting snow have developed pretty much everywhere along the
Arctic Coast. This storm moves inland over the next two days,
bringing accumulating snowfall to much of the Interior.

&&

.DISCUSSION...

Upper Levels and Analysis...
A powerful 485 dm 500 hpa low is centered over the Gulf of Anadyr,
with the surface low approximately at 948 mb. The upper trough
extends into the central North Pac, with the very impressive warm
conveyor belt stretching from 30N all the way to the high arctic
north of Wrangel Island. A basal shortwave trough is intensifying
over Bristol Bay, with this trailing surface low somewhere around
965 mb based on obs around that area. Heavy snow and local
blizzard conditions are occuring along much of the West Coast,
especially from Norton Sound northward. A rapidly tightening
pressure gradient is forcing an increasing Tanana Valley Jet as
well as a cross-Alaska Range gradient. Antler Creek, the normal
blow hole through Windy Pass, is pushing 70 mph already. Along the
North Slope, the easterly coastal jet is ramping up fast as the
warm advection across the Brooks Range induces a strong leeside
trough.

Central and Eastern Interior...
Gap winds in the Alaska Range and the Tanana Valley jet are
ramping up fast this morning, with hurricane force wind gusts
already through Windy Pass. The pressure gradient reaches max
intensity today, and we still expect strong gusts through the
Delta Junction area westward to Nenana, with southerly gusts to
70-80 mph through the AK Range passes. Winds completely end
tonight as the upper level trough axis brings in west winds.

Attention turns to snow moving into the INterior from west to
east, with the heaviest totals generally expected over the Central
Interior, slightly lesser values as the trough shifts east. Expect
1-3" by Thanksgiving morning, with some local 4-5" amounts
possible over the Central Interior. Some mixed freezing rain can't
be ruled out downwind of the AK Range late this evening and
tonight, but the chance is relatively low as most precipitation
will likely occur along and behind the cool front. Snow exits late
Thursday with mostly dry and cooling conditions on Friday and
Friday night.

West Coast and Western Interior...
The storm continues to pummel the coast with heavy snow/rain along
with blizzard conditions north of the Seward Peninsula. Strong
southeast winds continue to blow into the 35-55 mph range over
much of the coast as the surface low axis stretches from the Yukon
Delta northwest to the Gulf of Anadyr. As the trough shifts inland
tonight, snow will move into the Western Interior and exit the
coast, also bringing an end to blizzard conditions by this
evening. Inland areas will see a general 2-5" of snow with an
additional 1-3" along the coast, locally heavier up to 6 inches
along the northern Norton Sound coast. The front will clear the
Interior to the east for Thanksgiving Day, leaving behind it only
some snow showers until offshore flow on Friday completely dries
the entire region out. For coastal hazards, water levels will
quickly drop off this evening as the low moves inland and weakens.
See current coastal flood advisories and high surf advisories for
more detailed information.

North Slope and Brooks Range...
Blowing and drifting snow will impact the entire region as strong
east winds spread eastward through tomorrow as winds increase to
30-45 mph. Most locations will generally see vis reductions to 1/2
to 1 mile, but some local 1/4 mile vis is possible near the
immediate coast where ice leads may support light snow, as well.
The gradient relaxes Thursday as a front moves over the Brooks
Range, bringing light snow to the region just as winds are winding
down. East winds will remain blustery over the Northwest Arctic
through Fri night as a second much weaker front stalls over Cape
Lisburne.

Extended Forecast Days 4-7...
The extended forecast will start out pretty quiet as northeast
offshore over the West Coast dominates, keeping pretty much the
whole region on the dry side as storms roll through the Gulf of
Alaska. Southerly flow aloft begins to move into the Interior
late Saturday, increasing light snow threats into Monday, although
currently the pattern looks pretty benign. Things change on Monday
evening through Wednesday as an arctic trough drops into the West
Coast and southerly flow pumps moisture north across the Alaska
Range. A sharp baroclinic zone will develop somewhere over the
Western/Central Interior, with heavy snow possible in that area,
with warmer temps to the east. Stay tuned as this weather pattern
looks interesting...

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

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning for AKZ207-AKZ209.

High Wind Warning for AKZ223-AKZ225-AKZ226-AKZ227.

High Surf Advisory for AKZ211-AKZ213.

Coastal Flood Advisory for AKZ214.

Winter Weather Advisory for AKZ201-AKZ202-AKZ203-AKZ204-AKZ215-
AKZ216-AKZ219-AKZ221.

Winter Storm Warning for AKZ208-AKZ210-AKZ211-AKZ212-AKZ213.

Heavy Freezing Spray Warning for PKZ220-PKZ225-PKZ230.

Gale Warning for PKZ200-PKZ210-PKZ215-PKZ220-PKZ225-PKZ230-
PKZ235-PKZ240-PKZ245.

Small Craft Advisory for PKZ210.

&&

AHSENMACHER NOV 20

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FAIRBANKS AK
832 AM AKST WED NOV 25 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1153 AM     BLIZZARD         2 W KOTZEBUE            66.89N 162.61W
11/24/2020                   NORTHWEST ARCTIC   AK   ASOS

            THE KOTZEBUE ASOS REPORTED BLIZZARD
            CONDITIONS FOR 11 HOURS BEGINNING AT 11:53
            AM.

&&