Heavy Snow in Alaska, January 16 to 17, 2018

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
1251 PM AKST Tue Jan 16 2018

.DISCUSSION...

Models...Big picture short term solution continue to be in good
agreement. The details of course are lacking as you dig down in
scale. Temperature resolution is very important in this type of
situation and current models struggle with that. There is a warm
air intrusion in the low levels, but how far north that pushes
will control how far north the freezing rain extends. Surface
solutions matched up well against the 16/18Z analysis. Overall the
run to run has been good through the weekend, so will use an
almost equal blend for the short term with a lean toward the SREF
solution for precipitation probability. Extended solutions are in
much better agreement today than the last few days, so expect that
a blend of the current solutions and the ensembles will provide a
good solution for the extended periods.

Aloft...At 500 hpa...Flow aloft remains from the south, but much
lighter than the last few days. Ridge is over the Arctic Coast and
Western Brooks Range and will move offshore over the Arctic to
lie from south of Banks Island northwest across the Arctic over
76N 170W by Wednesday afternoon, then continues to by Thursday
morning with a 535 dam center over the Beaufort Sea. A 513 dam low
is moving over Kodiak Island this afternoon and will move over
the southwest mainland tonight as it weakens to 520 dam and
dissipates. A 522 dam low will develop over Fairbanks this evening
and move northwest over Ambler by Wednesday morning, then over
Point Lay Wednesday evening at 515 dam before moving over the
Chukchi Sea and dissipating. A 519 dam low will develop southwest
of Nunivak Island Wednesday evening and slowly drift south over
Bristol Bay by Friday morning. A weak ridge will build over the
Central and Eastern Interior Wednesday and dissipates Thursday. A
broad weak longwave trough will move over the state Friday. At 850
hpa...Zero isotherm is pushing west a bit today and tonight and
will lie from Old Crow YT to Livengood to McGrath with the warmer
air to the southeast. The warm air starts breaking up tonight, and
the airmass will start cooling. Patches of above zero
temperatures will linger over the interior and slowly cool through
Thursday morning. On the West coast the -10 isotherm is just
offshore and will move over the West Coast Wednesday night and
pushes into the Western Interior Friday as the cooling trend over
the state continues.

Surface...Stacked low moving over Kodiak Island with a 982 mb
center near Kodiak City by Wednesday morning. Weather front
associated with the low will be swinging north into the Eastern
and Central Interior this evening, and the Western Interior by
Wednesday morning. Elongated trough remains over the Western
Interior this evening with a 994 mb low near Noatak that will
slowly move north into the Chukchi Sea by Thursday morning and low
pressure extending south to the low over Kodiak. Weak trough
persists over the Arctic Plains and Coast and will be pushed
offshore and merge with the low as it moves into the Arctic, and
ridging from Siberia pushes east over the Plains and Brooks
Range. Ridging builds over the Yukon Territory behind the front,
and a 1001 mb high will be over the Yukon Territory by Thursday
morning with ridge of high pressure extending west to the Siberia.

Arctic Coast and Brooks Range...Very quiet. Some clouds over the
Northwest Coast associated with the low in the Chukchi Sea, bt
otherwise not much going on. Winds southeast becoming northeast
and increasing a bit to 10 to 20 mph for most areas. Increasing
clouds tonight over the Eastern Brooks Range will spread north and
west tomorrow with some light snow in most areas with up to 4
inches of accumulation locally. Blowing snow is expected to reduce
visibility in a few locations, but primarily along the Dalton
Highway. Temperatures steady today, but cooling as the week goes
on.

West Coast and Western Interior...Still some lingering flurries
over the area with mostly cloudy conditions. With the trough
remaining in the area, cloudy conditions will prevail and expect
some light snow at times tonight and tomorrow as the decaying
weather front moves into the area and eventually dissipates over
the coast. Snowfall amounts will generally be less than 2 inches.
There is a slight chance of freezing rain, mainly south of Kaltag
and east of Marshall tonight as some warm air gets pushed that
way. Winds generally less than 15 mph. Temperatures may warm a bit
south of Galena tonight, but most areas will be starting to cool.

Central and Eastern Interior...Precipitation already occuring in
the upper Tanana Valley and Fortymile Country with spits of
freezing rain. Heavier precipitation this afternoon, so Winter
Weather Advisories remain in effect, and expect accumulating
freezing rain this afternoon into early evening for areas south
of Livengood. Precipitation changing over to snow later this
evening with up to 2 inches of snow possible overnight. Winds will
remain light and variable in the interior, but expect gap winds to
develop in the Alaska Range as the surface low moves to the west a
bit and flow across the Alaska Range turns more from the south.
Gap winds gusting to 45 to 55 mph tonight will diminish tomorrow.
Behind the front also expect the Tanana Valley jet to set up as
the leeside trough develops so expect gusty winds to 45 mph around
Delta Wednesday morning into the afternoon. Temperatures slightly
warmer tonight, then cooling the remainder of the week.

&&

Coastal Hazards for days 3 and 4...None.

&&

Extended Forecast for days 4 to 7...Much better agreement in the
solutions with the latest runs. Strong cooling trend for the
extended periods, with some patchy clouds. Coldest air is expected
to remain over the West Coast and Western Interior, but much
colder temperatures are expected with some patchy flurries.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Winter Weather Advisory for AKZ215-AKZ216-AKZ220-AKZ221-AKZ222-
AKZ223-AKZ224-AKZ225-AKZ226-AKZ227.

Heavy Freezing Spray Warning for PKZ210.

Small Craft Advisory for PKZ210.

Brisk Wind Advisory for PKZ200-PKZ215-PKZ220-PKZ225-PKZ230-
PKZ235-PKZ240-PKZ245.

&&

SDB JAN 18