High Wind in Alaska, October 14 to 15, 2023

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
228 PM AKDT Sat Oct 14 2023

.SYNOPSIS...
Gradual warming continues across much of Alaska as a ridge of high
pressure in western Canada noses into the state. One more
disturbance tracks north around the ridge bringing precipitation to
parts of the region tonight into Sunday. Accumulating snow is
expected across much of central Alaska northward to the North Slope
where several inches is expected. To the east, precipitation chances
decrease and warming temperatures make precipitation type more
complicated. Areas of rain and freezing rain are possible. The
next significant feature will be a trough moving in from Siberia
for the middle of the week that will bring with it another chance
of snow, wind, and colder temperatures.

&&

.DISCUSSION...

Upper levels and analysis...

The upper trough over western Alaska has continued to weaken, with
much of its energy being pulled southward into the Gulf of Alaska
where several storms have tracked over the past week. Ridging over
Canada has already pushed into eastern Alaska where mid level
temperatures have warmed above freezing. This leads to a more
complex precipitation type forecast.

The next, and final, in the parade of remnant shortwaves tracking
north from the Gulf of Alaska around the ridge, moves in tonight
and pushes to the Arctic coast on Sunday. This will bring one more
period of precipitation with it as it moves through.

On Monday into Tuesday the last bit of the western trough gets
absorbed in advance of a larger trough moving east out of
Siberia.

Model Discussion...

There is pretty descent agreement in the models on the shortwave
tracking north tonight into Sunday. Most of the guidance produces
a tenth to a quarter of an inch of liquid equivalent
precipitation in the core of the track, with the heaviest amounts
being toward the south slopes of the Brooks Range. Higher end
amounts up to 0.5 inch are possible. Amounts decrease to the east,
especially east and southeast of Fairbanks where precipitation
chances overall are much lower.

Models disagree on how to end the existence of the western Alaska
trough. The GFS pulls it northeast through northwest Alaska in
advance of the Siberian wave. Meanwhile the CMC and ECMWF pull it
south into the Gulf of Alaska low. The GFS solution would keep
some chances for snow near this low on Monday while the southern
track would be drier.

Central and Eastern Interior...

Our last shortwave trough moving north tonight into Sunday brings
the best precipitation chances to the western portion of the
region. From Tanana to Bettles and into the south slopes of the
Brooks Range stand the best chance of seeing significant
precipitation. Further east chances decrease pretty quickly.
Precipitation type is a bit complex as warm air has already begun
to move in aloft across the eastern portion of Alaska, leading to
areas of rain or freezing rain depending on surface temperatures.
Chances in this area are lower overall, and amounts should be too
if it does occur. Significant icing impacts are not expected to
infrastructure, but exposed roadways and other surfaces could see
a glaze of ice. This is most likely north of Fairbanks on the
Dalton Highway. Winter Weather Advisories have been posted for the
threat for a glaze of ice. Further west, precipitation type stays
mainly snow, with amounts of 3 to 6 inches possible north of the
Yukon River in the south slopes of the Brooks Range. Winter
Weather Advisories have been posted here as well.

Ridging is strongest on Monday and will likely bring the best
weather of the stretch. Most areas see temperatures rise to
freezing or above including some low 40s possible.

West Coast and Western Interior...

Snow from the next shortwave trough stays largely east of this
region tonight and Sunday with temperatures warming to the low to
mid 30s Sunday and Monday. Some uncertainty begins Monday into
Tuesday with respect to the progression of what's left of the
western Alaska trough. If the GFS is right and the trough tracks
northeast, it may lead to an area of light snow Monday into Monday
night. If it instead moves south, then precipitation chances will
be lower with temperatures perhaps a bit warmer as well.

North Slope and Brooks Range...

Periods of snow are expected in the Brooks Range and North Slope
region now through Sunday. The last in a series of shortwaves
moves north through the area on Sunday bringing the most
widespread snow. Storm total amounts of 3 to 6 inches are
possible where snow is heaviest, though amounts decrease to the
north and west. To the east, warmer temperatures aloft may lead to
a transition to freezing rain as the dominant precipitation type
close to the Canada border. A Winter Weather Advisory has been
issued here where a glaze of ice on exposed surfaces is possible.

Extended Forecast Days 4-7...

A Siberian trough moves east into Alaska on Wednesday, breaking
down the ridge and ushering in a pattern change. There are still
timing, track, and intensity differences among the models, but the
general idea of a strong trough replacing the ridge is consistent.

As the trough arrives, it could bring with it a more substantial
surface low tracking toward the Seward Peninsula. Snow is likely
ahead of this low, with stronger winds possible behind it. Just
how strong and what locations will be impacted is still unclear
due to the track and intensity differences in the models. At the
moment it appears winds may stay below advisory levels for most of
western Alaska, but there could be some coastal flood impacts as
high surf heads toward the coast.

With the shift from upper ridging back to upper troughing,
temperatures will head back down again as well. Although we do
shift back to below normal, the change won't be that noticeable
over western Alaska where temperatures really only fall by about 5
degrees. It will be more noticeable as the colder air arrives in
the eastern half of the state where temperatures fall from their
peaks in the 40s early this week back down to highs only in the
teens and 20s. Lows vary based on overnight cloud cover and the
ability of the inversion to really set up.

Coastal Hazard Potential Days 3 and 4...None.
There is a chance of coastal flooding from the Bering Straight
northward Wednesday into Thursday.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Winter Weather Advisory for AKZ811-832>834-846.
     Winter Weather Advisory for AKZ812-831.
     Winter Weather Advisory for AKZ839>841-843>845-847-848.
     Winter Weather Advisory for AKZ805.
     Wind Advisory for AKZ849-850.
PK...Small Craft Advisory for PKZ817.
     Small Craft Advisory for PKZ854.
&&