Heavy Freezing Spray Warning 18, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
316 PM AKDT Sat Oct 30 2021

.SYNOPSIS...
A very strong storm now moving north over Western Alaska will
move over NW Alaska Sun and then move into the Chukchi Sea and
restrengthen Sun PM and Mon. This is causing heavy snow over the
Western Interior that will spread northwest to portions of the
West Coast tonight, then move back east over the Western Interior
on Sun PM, before tapering off and moving east into the Eastern
Interior on Mon.

This storm is causing high winds over the Alaska Range that will
last through Sun night. This is also causing temperatures in the
30s and lower 40s over the Eastern Interior along with gusting
east winds that will last  through Sun.

This storm will cause strong south winds over the Brooks Range
tonight through Sun night and cause snow and blowing snow issues
in Brooks Range Passes through Sun night.

This storm is causing heavy snow over the Western Interior and
portions of the West Coast and Central Brooks Range that will
continue into Sun with storm totals of 6-12 inches. The heaviest
snow will be north and west of Kobuk to Galena to Shageluk today
through Sun. Expect snow to change over to rain or possibly brief
freezing rain southeast of Kobuk to Galena to Shageluk today and
tonight, with a chance of rain and freezing rain on the North
Slope east of Utqiagvik on Sun. Precipitation should change back
to all snow on Sun night and Mon.

This storm will cause northwest winds 20-30 kt and high surf
along the Chukchi Sea Coast from Shishmaref to Point Hope from
Sun PM into Mon AM. This storm will cause southwest winds 25 to
35kt and high surf along the Arctic Coast from Point Lay to Point
Barrow from late Sun night through late Mon night. There is a
chance of low visibility in blowing snow along the Arctic Coast on
Mon, but at this time it looks like the strong winds will occur
after the snow has tapering off.

A second storm moving into the Northern Bering Sea on Mon and to
the Southern Chukchi Sea on Tue will bring more stormy weather to
the West Coast Mon and Tue.

&&

.DISCUSSION...
Models initialize well aloft at 12Z and show similar solutions
through 4pm Sun. After that time, the NAM/ECMF and Canadian
models all deepen the low aloft/short wave over NW Alaska and the
Chukchi Sea much more than the GFS. It appears as through the
frontal wave moving north on Sun taps into very cold low level air
off of Siberia once it gets over the Chukchi Sea which should
cause this strengthening and deepening. Since the NAM deepens this
more than any other models, we prefer the NAM solution. The set
up is there for deepening aloft with the cold air to be tapped
into at low levels, and the still open water of the Chukchi Sea to
cause surface level heating and thus surface level pressure
lowering.

850 MB temperatures rise above freezing southeast of the warm
front on all models. Expect snow to change over to rain or
possibly brief freezing rain southeast of Kobuk to Galena to
Shageluk today and tonight, and on the North Slope east of
Utqiagvik on Sun. Precipitation should change back to all snow as
the cold front moves east on Sun night and Mon.

With precipitation, models show similar areal coverage and
amounts through Sun morning, then the NAM and ECMF move the precip
to the east more quickly than the GFS Sun PM into Mon and Tue.
Since the NAM and ECMF are the preferred solutions aloft, with
the NAM preferred at the surface, will use the NAM for
precipitation location and amounts, but blend in a minor portion
of the ECMF while excluding the GFS precip.

At the surface at 15Z, models all verify well at the surface.
Models show similar solutions through tonight, and then the all
models deepen the triple point low moving over NW Alaska on Sun,
with the NAM deepening it the most, the ECMF and Canadian
deepening it almost as much as the NAM, but the GFS being
significantly weaker. Since this is a set up for rapid deepening
as the low taps into the cold air of Siberia Sun, and then moves
over the warm water of the Chukchi Sea on Mon, we favor the
deepest solution, which will likely be the NAM. In fact, this set
up could well be deeper than the NAM, but we will go with the NAM
at this point in time for the surface fields and winds.

Bottom line for models is that we will generally use the NAM,
blending in the ECMF in a minor way for precip. Expect snow to
change over to rain or possibly brief freezing rain southeast of
Kobuk to Galena to Shageluk today and tonight, and on the North
Slope east of Utqiagvik on Sun. Precipitation should change back
to all snow as the cold front moves east on Sun night and Mon.

Coastal Hazard Potential Days 3 and 4...
Chukchi Sea Coast from Shishmaref to Point Hope will see
northwest winds 20-30 kt and high surf Sun PM into Mon AM.

Arctic Coast from Point Lay to Point Barrow will see southwest
winds 25 to 35kt and high surf along the Arctic Coast from late
Sun night through late Mon night.

High surf possible Norton Sound Coast Mon and Tue, and Southern
Chukchi Sea Coast on Tue.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory for AKZ201-AKZ202-AKZ207-AKZ209.

Winter Storm Warning for AKZ208-AKZ209-AKZ212-AKZ215-AKZ216-
AKZ217.

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

Winter Weather Advisory for AKZ206-AKZ218-AKZ219-AKZ220-AKZ227.

Heavy Freezing Spray Warning for PKZ200-PKZ220-PKZ225-PKZ230-
PKZ235-PKZ500.

Small Craft Advisory for PKZ200-PKZ210-PKZ215-PKZ220-PKZ230-
PKZ235-PKZ240.

Gale Warning for PKZ225-PKZ500.
&&

JB OCT 21