Small Craft Advisory 114, NWS Fairbanks, AK

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
430 AM AKDT Tue Sep 12 2017

.DISCUSSION...

Models...There is good agreement in the short term solutions
today with the trough digging south over the Dateline, and the
ridge building north over the Yukon Territory and Beaufort Sea
over the next 24 hours. Over the West Coast several shortwaves
will be moving up the back of the ridge rapidly, but individually
it will be impossible to time each one of them. A long fetch of
moisture is being pulled into the flow, over the West Coast and
Western Brooks Range, from over the Pacific. Will be leaning a bit
more on the NAM since it handles the downslope effect better in
the interior.

Aloft at 500 hpa...A 518 dam low is high in the Canadian
Archipelago with troughing extending southwest to a 519 dam low
over Wrangel Island, while a 534 dam low is pushing southeast over
the Pribilof Island this morning. Ridging is building north this
morning with 564 dam heights over the Gulf of Alaska coast, and
540 dam heights over the northwest coast. By Wednesday morning the
low high in the Canadian Archipelago will weaken to 522 dam with
troughing southeast to a 519 dam low over Wrangel Island, and the
534 dam low will dissipate. The ridging will continue to build as
it slips east with 570 dam heights pushing north to Yakutat, and
540 dam heights extending over the northern Beaufort Sea. By
Wednesday evening southwest flow will dominate over the state and
a strong shortwave in the flow will move to the Pribilof Islands
before it changes course and starts moving northeast across the
state Thursday. Ridging will build back west across the interior
behind the shortwave Friday and the trough over the Bering Sea
will dig south. At 850 hpa...Warm air pushing north as the ridging
builds in. The zero isotherm will move north to the Arctic Coast
today and push north of the Central and Eastern Arctic Coast
tonight. Out west the zero isotherm will lie from Point Lay to
Brevig Mission and south of St Lawrence Island this afternoon, and
be Wednesday evening it will lie from Wainwright to Kotzebue to
Nunivak Island as cold air continues to be pushed south.

Surface...Weak ridge of high pressure over the Eastern Interior
will hold today, but be pushed east tonight. Front lies over the
Arctic Coast with a 984 mb low over the Chukchi Sea and a cold
front extending south to Nome, then southwest to St Matthew Island
and into the central Bering Sea. The front will remain nearly
stationary as the low in the Chukchi Sea moves to 100 nm
northeast of Wrangel Island at 991 mb. Leeside troughing north of
the Brooks and Alaska Ranges. Strong pressure gradient developing
on the north slopes of both ranges will produce some locally gusty
winds. A 1029 mb high over the north Pacific will move northeast
over the eastern Gulf of Alaska today, then drift south Wednesday.
A 1020 mb high over the Matanuska Valley will drift east over the
Copper River Basin as it builds to 1022 mb Wednesday morning. The
front out west will continue to drag north over the West Coast
into Friday before the southwest flow breaks down as ridging
builds west from the interior to the coast. A 989 mb low will
move from the north Pacific to the Pribilofs by Friday morning,
but models disagree on where is goes after that.

Arctic Coast and Brooks Range...From Point Barrow to Atigun Pass
and areas west, cloudy with showers. May start as snow in the
Brooks Range above 2000 feet, but will change over later this
morning as warm air surges north. Expect a dry area just north of
the Brooks Range and over the Central and Eastern Arctic Coast
mainly east of Point Barrow with the persistent southwest flow
across the Brooks Range. Temperatures warming a bit the next few
days in the same area, while temperatures over the northwest coast
will be a bit cooler with north flow. Heaviest precipitation will
be along the crest of the Brooks Range.

West Coast and Western Interior...Rain, rain and fog, and more
rain over the next couple days. Strong southwest flow pulling
moisture from the north Pacific will produce almost constant
rainfall through early Friday morning before tapering off.
Heaviest rainfall will be in the Upper Kobuk and Noatak Valleys
with nearly 5 inches of rain possible. Rainfall amounts for the
remainder of the area will be around 0.50 to 1.50 inches. Patchy
fog will impact visibility at times. Winds will be dependent on
the location of the front with winds to the west of the front from
the northwest to north at 5 to 15 mph and winds to the east of the
front from the east and southeast at 10 to 25 mph. Temperatures
inland a bit warmer as warm air is pulled north, with over the
Capes and Bering Strait/St Lawrence Island it will be a bit cooler
with as cold air is pushed south.

Central and Eastern Interior...Kind of tricky forecast with the
southwest flow. Some snow above 2500 feet north of Coldfoot and
from Arctic Village north so will maintain the Winter Weather
Advisory, otherwise expect rain northwest of a line from Lake
Minchumina to Fort Yukon to Old Crow YT, to the southeast of the
line just a slight chance of rain. Strong pressure gradient
setting up as leeside troughing develops and bubble high moves
from Matanuska Valley to Copper River Basin tonight. Will issue a
Wind Advisory for zone 226 passes and vicinity. Temperatures
warming 3 to 7 degrees as ridging builds north and downslope
decreases clouds from Fairbanks southeast.

&&

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

&&

.Hydrology...Rain, 0.50 to 5.00 inches, out west will produce
rises in the rivers with sand bars disappearing and back sloughs
filling. Small streams from the Seward Peninsula to the Western
and Central Brooks Range will rise to bankfull with the potential
for some localized flooding.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...

Flood Advisory for AKZ208-AKZ209-AKZ210-AKZ211-AKZ212-AKZ213-
AKZ216-AKZ217.

Gale Warning for PKZ200.

Small Craft Advisory for PKZ210-PKZ215-PKZ220-PKZ225-PKZ230-
PKZ235-PKZ240.

&&

SDB SEP 17