Blizzard in Alaska, February 22 to 24, 2017

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
134 PM AKST Tue Feb 21 2017

.DISCUSSION...

Models...Are in relatively good agreement out into the extended
periods. Timing of the shortwaves that will be moving through the
primarily zonal flow that develops over northern Alaska will make
for an active pattern the remainder of the week. A blend of the
models will be the best solution at the moment with a lean toward
the GFS later in the extended periods to give a little more
enhancement to the shortwave moving across the area early next
week.

Aloft...At 500 hpa...Trough over the west coast with a 506 dam
center over Point Lay has a shortwave extending southeast that has
rotated north of Fairbanks this afternoon. The low drifts
northeast toward Barrow tonight and the trough rotates over the
arctic coast by Wednesday morning. Weak ridging behind the
shortwave will push 522 dam heights to the north of Fairbanks
tonight as the ridge axis moves east. A rapidly moving shortwave
over the southeast Bering Sea this afternoon will move over the
southwest mainland this evening south of Norton Sound and lie over
Tanana to Anchorage by Wednesday morning, then over the AlCan
border from Eagle south Wednesday afternoon. The 506 dam center
will start filling and move off to the east Wednesday night as the
next ridge pushes east over the eastern Bering Sea and west coast
Wednesday evening. By Thursday morning the ridge will lie over
Point Lay to Ruby to Homer, and by Thursday evening will lie from
Barter Island to Ft Yukon to Valdez as it rotates east around the
570 dam center in the northeast Pacific. As the ridge flattens out
the next shortwave will move over the west coast Friday afternoon
and across the interior overnight as the zonal flow develops and
a series of shortwaves flow across the state. At 850 hpa...-20
isotherm lies from Nome to Fairbanks this afternoon and will
slide north to lie from Brevig Mission to Bettles to Old Crow YT
Wednesday morning. The zero isotherm lies well south of our
forecast area but will push to the north over the Lower Yukon and
Kuskokwim Deltas Thursday morning before being pushed back to the
south.

Surface...Surface ridging with a 1025 mb center over the middle
Yukon River Valley this morning will move east with the center
over the middle Koyukuk River Valley this afternoon, and moving
over the Upper Yukon Flats this evening at 1027 mb. Leeside
troughing develops this evening north of the Alaska Range in
advance of the rapidly moving low pressure system that will be
over Bethel this evening at 1001 mb. The low will move to
Kantishnaby Wednesday morning with a second low developing over
Kodiak Island tonight and moving south of Prince William Sound.
The low in the interior will move across the Fairbanks area around
noon Wednesday with weak troughing over most of the interior. A
trough will hang over the arctic just offshore. Ridging will build
east over the Brooks Range and arctic plain as a 1034 mb center
develops in the upper Kobuk Wednesday afternoon with ridging
extending south to Cook inlet, and northwest to a 1046 mb center
over the Siberian arctic. The ridge moves over the central Brooks
Range Early Thursday morning and over the eastern Brooks Range by
Noon Thursday with ridging over the eastern half of the state.
Ridging will break down Saturday as a more progressive pattern
develops.

Arctic Coast and Brooks Range...A trough of low pressure will
persist over the area tonight, but drift slowly offshore as weak
ridge of high pressure develops over the plains. This should allow
for some clearing inland, but the stratus will persist over the
coastal areas. A little bit of a cooling trend as the cold air
over the interior moves north across the area. West to southwest
winds becoming northwest Wednesday and southeast Thursday. Wind
speeds generally 5 to 15 mph. Chance of snow will continue for the
coastal areas with increasing chance of snow in the eastern
Brooks Range as the low moves south of the area.

West Coast and Western Interior...Going to be busy out west as
the systems move through the area. Warming a bit with the first
system which will primarily impact areas south of Norton Sound
tonight, then from the Middle Yukon River Valley south Wednesday
morning and afternoon. A surge of warm air into the area could
make things interesting as the snow could change to freezing rain
for a short period Wednesday morning south of St Michael. Even if
it doesn't expect some ice pellets to mix with the snow in the
Lower Yukon Delta. Snow amounts next 24 hours up to 4 inches with
the heaviest amounts in the upper Kuskokwim River Valley. After a
short break the next system will move the to the eastern Bering
Sea Wednesday evening spreading snow to The lower Yukon Delta as
well as St Lawrence Island and the Bering Strait, and eventually
to the remainder of the area by Thursday morning. Look for
improving conditions Friday. Winds will pick up over the Bering
Strait and lower Yukon Delta Thursday. The strongest winds will be
on St Lawrence Island and through the Bering Strait bringing
Blizzard Conditions to the area. Will issue Blizzard Warning for
Zone 213 and Winter Weather Advisories for zone 211, 212, and 214
primarily for blowing snow with poor visibility. Will maintain the
Watches for the other areas.

Central and Eastern Interior...Snow has moved into the southwest
mainland and will move into the Central Interior around midnight
with the snow continuing through Wednesday. Expect a break in the
snow between systems on Thursday. Snowfall amounts up to 4 inches
Wednesday with the heaviest amounts over the middle Tanana Valley.
A second snow event on Thursday will bring another 1 to 3 inches
of snow. Temperatures will fall early tonight then start rising
before morning as the clouds move into the area. Winds generally
light and variable except for gap winds in the Alaska Range that
will kick up later this evening. Near Parks Highway passes expect
gusts to around 40 mph while south of Delta junction winds will
be gusting to around 50 mph so will issue a Wind Advisory for the
Eastern Alaska Range.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Wind Advisory for AKZ226.

Winter Storm Watch for AKZ207-AKZ208-AKZ209-AKZ210-AKZ217.

Blizzard Warning for AKZ213.

Winter Weather Advisory for AKZ211-AKZ212-AKZ214.

Gale Warning for PKZ210.

Brisk Wind Advisory for PKZ200.

&&

SDB FEB 17