Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 212352

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
352 PM AKDT FRI OCT 21 2016

The 12Z 500 mb analysis shows 495 dm low in the high arctic,
located near 79.3N 173.7E. Troughing extends south of this low
with the through axis running through central Alaska. Further
upstream short wave ridging continues to amplify over the
northern Pacific with axis located near 170E, extending northwestward
through eastern Siberia. Further west, a 508 dm low was seen over
the north Pacific about 250 miles southeast of the tip of the
Kamchatka Peninsula. At the surface, 18Z analysis shows broad low
pressure over the high arctic at 997 mb near 73N 159W. Low
pressure at 989 mb was seen over the northern Pacific south of the
Gulf of Alaska around 200 miles west southwest of Ketchikan. High
pressure at 1025 mb was seen over the central Bering Sea around
200 miles southeast of Gambell.

The 12Z deterministic models have come into better agreement on
the overall weather pattern into next week, certainly better than
what was observed 24 hours ago. It is still shaping up to be an
active week on portions of the west coast, more on that and high
surf/coastal flooding potential below. In the shorter term, upper
low in the high arctic will continue to shift east toward the
Canadian Archipelago by Sunday morning, as short wave ridging
builds into southwestern Alaska. Further upstream, a 508 dm upper
low will move into the western Bering Sea by Sunday and swing
northward as an open wave into the Chukotsk Peninsula by Sunday
evening. This piece of energy will enter eastern Siberia and merge
with much broader cyclonic flow that will develop over this region.
This will set the stage for multiple rounds of low pressure, one
or more potentially strong, to swing up northward through the
Bering Sea and Bering Strait next week.

North Slope: Sea effect/enhanced snow showers will persist across
the region through at least Saturday under broad moist cyclonic
flow stationed in the high arctic. A weak surface trough will
swing across the arctic coast this evening, which will help
continue to enhance these snow showers, as well as help
reinvigorate surface winds between 20 to 30 mph which will lead to
blowing and drifting snow. A ridge of high pressure will build
over the Alaska mainland on Sunday with upper level flow turning
to the southwest along with temperatures warming aloft, helping to
end the snow showers across the region. Snowfall amounts will
generally remain light across the arctic coast, with around 1 to 3
inches expected over the next 24 to 36 hours.

West Coast: No major concerns through the weekend. Expecting some
sea effect snow showers along the coast mainly north of the
Seward Peninsula through tonight before wind direction and
temperatures aloft associated with building high pressure help
bring and end to these showers. A shortwave trough will exit the
Siberian arctic coast and cross the Chukchi Sea tonight, moving
across the northern half of the state Saturday. This feature
combined with the existing broad low pressure in the high arctic
will bring a round of light snow to the western Brooks Range and
the upper Kobuk/Noatak Valleys on Saturday with around 1 to 3
inches of accumulation expected. High pressure looks to bring
precipitation free conditions for most locations through Monday
before a series of weather fronts out ahead of a series of low
pressure systems moving through the Bering Sea bring a chance of
rain and snow to the west coast.

Interior: Upper trough axis will continue to push into the far
east interior overnight. Low stratus and flurries currently exist
from Old Crow to Nenana to McGrath and should gradually shift
east yielding clearing skies from west to east tonight. Light
accumulating snow is currently falling this afternoon along a line
from Fort McPherson to Delta Junction to Eureka, and expecting
this area to shift east over the far southeast Interior by
Saturday morning. Expecting an additional 1 to 2 inches of snow
from aforementioned line east by late Saturday. Elected to extend
the Winter Weather Advisory for zone 226 until midnight as snow
continues to fall in this zone with total snow accumulations
around 4 to 7 inches, heaviest west of the Richardson Highway.
Otherwise high pressure will reassert itself over eastern Alaska
which will likely bring fair weather and precipitation-free
conditions through next week. Some weather fronts moving in form
the west coast may bring very low chances of snow, or mixed rain
and snow to the interior during the middle and latter parts of the

Coastal Hazard Potential Days 3 and 4...Confidence is building
that a significant Bering Sea storm will move north through the
Bering Sea on Tuesday, likely below 950 mb with a good chance of
this low pressure dropping below 940 mb. The deterministic runs
seen today have come into better agreement with the 12Z ECMWF
actualy coming more in line with the NAEFS and GFS solutions
favoring a more westerly track west of Saint Lawrence Island and
toward the Gulf of Anadyr. However, a good degree of uncertainty
remains with the final track and strength of this system as some
ensemble members from the ECMWF favor a track up the Bering closer
to mainland Alaska. In either case, expecting strong south to
southeast winds across the Bering Strait and west coast of Alaska
Monday night into Tuesday and Tuesday night, likely at least gale
force. Locations favored for high surf and coastal flooding
conditons in this regime include Point Hope, Kivalina, Brevig
Mission, Nome, Golovin and possibly Shaktoolik. Fortunately this
system looks to be rather fast moving which would prevent surge
values from getting too high, favoring more of a high surf/beach
erosion scenerio opposed to moderate or major coastal
flooding/inundation. Many details still need to be clarified as
the guidance converges on a more common solution, and surge
guidance for this event becomes available...stay tuned.


Winter Weather Advisory for AKZ226.

Heavy Freezing Spray Warning for PKZ235-PKZ240-PKZ245.

Small Craft Advisory for PKZ210-PKZ235-PKZ240-PKZ245.


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