Area Forecast Discussion
Issued by NWS Fairbanks, AK

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129
FXAK69 PAFG 191349
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
549 AM AKDT Thu Oct 19 2017

.SYNOPSIS...
Aloft...
A long wave trough over mainland Alaska will deepen through the
Fri and then persist through the weekend. A 995 DM low at H500 180
nm northwest of Barrow will move to Point Lay by 4pm Thu, to 60 nm
west of Kivalina by 4am Fri, to Nome by 4pm Fri and then over
Norton Sound Fri night and Sat. Very cold air associated with this
feature is moving over open water and causing a strong surface low
to form under this feature that will track directly under this
feature and form heavy snow showers over the open water due to
nearly dry adiabatic lapse rates with 850 mb temperatures of -12C
or colder. See the surface feature mentioned below for details.

Northern Alaska will remain cold through the weekend, with snowy
conditions along the coasts.

Surface...
A 980 mb low 180 nm northwest of Barrow will move to near Point
lay as a 980 mb low by 4pm Thu, to 60 nm west of Kivalina as a 980
mb low by 4am Fri, to near Nome as a 985 mb low by 4pm Fri then
weak slowly. A cold front stretching from this low to the Bering
Strait will move to Point Lay to the Yukon Delta by 4pm Thu, to
Kivalina to Anvik by 4am Fri, and to Kotzebue to Anvik by 4pm Fri.
Very cold air with the low and behind the cold front are causing
very unstable conditions and heavy snow showers near the low
center and along the cold front. Showers will taper off as the
front moves inland. Expect at least 2 inches of snow every 12
hours near the low center. Showers along the front taper off as
the front moves inland. There are northwest winds 20-30kt along
and following the cold front. There are north to northeast gale
force winds in the northwest quadrant of the low. Winds will
decrease in the wake of the low.

This feature is causing periods of low visibility with the snow
showers over zones 201 and 202 so winter weather advisory will
continue there today. May need to issue winter weather advisory
for zones 213 and 207 tonight.

A 992 mb low 60 nm north of Barter Island will persist through
Friday, then move to near Barrow as a 992 mb low by 4am Sat.
Snow along and north of this low will remain mainly offshore
through Fri then move into Barrow Fri night.

An occluded front stretching from Yakutat to Inuvik will persist
through tonight then dissipate Fri. This is causing light snow
along the Alcan Border and Alaska Range that will taper off
tonight. This is also causing nw winds 10g20 mph through the
Alaska Range passes and over the eastern Tanana Valley today that
will taper off tonight.

&&

.DISCUSSION...
ECMF again moves the low aloft southwest more quickly than the
GFS and NAM, and we favor the slower GFS as the low is now slowing
as it moves over open water deepens at the surface. At 06Z the
low near Point Thompson is 5 mb deeper than models initialize and
the low north of Barrow is almost 10mb deeper than any models
indicate. Due to this expect the low to remain deeper and move a
bit slower than any models indicate. Will lean towards the GFS
since it has the slowest movement of any deterministic models,
but we will move the low center a bit slower than the GFS. What
this means is that snow will last longer over the Western North
Slope than models indicate, and that NW winds in the southwest
quadrant of the low will last longer and be stronger than models
indicate. Since winds have now turned NW at Shishmaref and could
last through tonight we will issue a high surf for that area.

This also means that the deeper low near Barter Island will lead
to winds lasting longer today in zone 204 than indicated by
previous forecasts and by models.

By Fri afternoon, model locations for the low come together
better near Nome and seem reasonable.


Coastal Hazard Potential Days 3 and 4...
There are northwest winds 20-30kt blowing across the southern
Chukchi Sea causing high surf at Shishmaref today through tonight.
Winds will decrease and turn northeast at Shishmaref Friday
morning causing surf to decrease.

May see High surf at the Bering Strait and and St Lawrence Island
tonight and Fri as the strong winds just west and north of the low
move over those areas.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory for AKZ207.

Winter Weather Advisory for AKZ201-AKZ202.

Heavy Freezing Spray Warning for PKZ230-PKZ235-PKZ240-PKZ245.

Gale Warning for PKZ225-PKZ230-PKZ235.

Small Craft Advisory for PKZ210-PKZ220-PKZ225.
&&

$$

JB OCT 17



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