Small Craft Advisory 239, NWS Fairbanks, AK

Northern Alaska Forecast Discussion...CORRECTED
National Weather Service Fairbanks AK
311 PM AKST Thu Dec 14 2017

.DISCUSSION...
The persistent southerly flow pattern that has been over the
forecast over a week looks to finally break down this weekend. The
models are in good agreement through the weekend in terms of the
major synoptic scale features.

Aloft, at 500 mb, the southerly flow pattern continues over
northern Alaska, although the flow aloft weakened overnight. A
501 dam low that is currently moving to the east along the
Aleutian Chain will move into the Yukon Delta area by Saturday
morning. As the low move east the southerly flow aloft over the
Interior/Alaksa Range will intensify, particularly Friday evening
into early Saturday. By Sunday morning the low will move into the
Gulf of Alaska turning the flow aloft over northern Alaska more
westerly. The pattern aloft early next week looks to be more
progressive; however, the models sill differ in the exact details.

Central and Eastern Interior: A front associated with a low that
is currently in the northern Gulf of Alaska will move north and
west through the eastern Interior today into Friday. Models are
in good agreement of a cooling trend aloft. This means that any
precipitation will fall as snow. This system will bring 1 to 3
inches of snow as it moves through. For Fairbanks the best window
for snow will be from 9 PM this evening through 9 AM Friday
morning. As the upper level low moves into the Yukon Delta the
flow aloft over the Interior will strengthen. This, when combined
with the leeside trough strengthening north of the Alaska Range
will lead to strong southerly winds to develop in the Passes of
the Alaska Range late Friday morning. Current guidance suggests
that the winds will peak Friday evening before subsiding early
Saturday morning. Current thinking is that the wind speeds will
remain just below advisory criteria; however, it will be close and
future shifts will have to continue to monitor the situation.
Over the past week the models havn't had the best run-to-run
consistency in terms of the timing of the strong wind events in
the Alaska Range and I suspect that this event may have similar
issues. A front will move from south to north over the Interior
Saturday into Sunday bringing another round of snow; however, the
models currently differ timing and QPF with this system. The
models are also front moving eastward across the central Interior
Tuesday evening and into the Eastern Interior Wednesday.

North Slope and Brooks Range. The pressure gradient across the
north slope will decrease this evening as a low just north of the
Bering Strait weakens and moves west. This will cause a decreasing
trend in the winds along the coast this evening. I cancelled the
Blizzard warnings that were out along the Arctic Coast due to
winds decreasing and visibilities improving. I opted a put out a
Winter Weather Advisory for zone 201 through midnight since some
blowing snow is expected reducing the visibility to a half mile
at times. Some falling snow is expected this evening although the
timing of this will correspond with a decrease in winds. Some
light snow is possible through Saturday evening along the coast.

West Coast and Western Interior: Widespread areas of fog expected
across much of the west coast and western Interior. This is
mainly due to cooler temperatures combined with ample moisture at
the surfaces as a result of melting associated with recent warm
conditons. A weather front associated with a low in the Bering Sea
will cause the winds to increase south of the Bering Strait
tomorrow. This front will also bring 1 to 2 inches of snow. Snow
with this front will move into the Yukon Delta and lower Yukon
Valley tomorrow afternoon and will spread north over the west
coast and western Interior (as far north as the Bering Strait)
through early Saturday morning. Snowfall is expected from a front
that will move through the western Interior Saturday afternoon
into Sunday, although the models differ on the exact details at
this moment. A weather front associated with a low in eastern
Russia will move through the Bering Sea on Monday and will reach
the west coast Monday evening. This front look to push eastward
across the forecast area through Wednesday morning. The models
seem to have the same general idea with this front but differer on
the timing, wind speeds and QPF amounts. This front will bring
strong southeasterly winds as it moves through the Bering Sea and

Coastal Hazard Potential Days 3 and 4...A weather front that will
move through the Bering Sea on Monday and will reach the west
coast Monday evening will may bring some high surf to any coastal
areas that are ice free (mainly the south side of St Lawrence
Island). At this point neither the direction nor the duration of
the wind looks to be favorable for coastal flooding in areas that
are ice free.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory for AKZ201.

Heavy Freezing Spray Warning for PKZ210-PKZ220.

Small Craft Advisory for PKZ210.

Brisk Wind Advisory for PKZ200-PKZ225-PKZ230-PKZ235.
&&

DEC 17