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Northern Alaska forecast discussion 
National Weather Service Fairbanks Alaska
409 PM akdt Sat Oct 22 2016

the 12z 500 mb analysis continues to show 498 dm low in the
central Beaufort Sea, located near 77.5n 151.2w. Troughing
extended south of this low with the through axis running from
Point Thompson to Arctic Village to Fort Yukon to Delta Junction,
extending to a 525 dm low in the Gulf of Alaska. Upstream ridging
continues to build in over the central Bering Sea now extending
into southwestern Alaska. Further west, a 513 dm low was seen
over the North Pacific about 450 miles southwest of Attu Island.
At the surface, 18z analysis shows weakening low pressure near the
Canadian archipelago near 78n 132w. Broadening high pressure at
1026 mb continues to build over Mainland Alaska. Low pressure at a
972 mb was seen around 100 miles southwest of Attu Island.

The 12z deterministic models continue to converge on a common
solution on the overall weather pattern into early next week. 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 northeastward toward the pole, as ridging
builds into Mainland Alaska Sunday. Further upstream, 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
become a part of larger scale cyclonic flow centered over eastern
Siberia and the western Bering Sea. This will set the stage for
multiple rounds of low pressure to swing up northward through the
Bering Sea and Bering Strait next week.

North slope: sea effect/enhanced will continue through this
evning, currently being enhanced by an upper level short wave
trough which is moving rapidly through northwest Alaska this
evening. 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 late tonight into tomorrow. Relatively
quiet conditions are expected for the upcoming week with little to
no precipitation expected along with lighter winds. Some weakening
weather fronts from low pressure systems moving up the Bering Sea
will bring low chances of snow mainly west of Barrow mid to late

West coast: main focus will be rather stormy conditions expected
for the Bering Sea for this week.

No major concerns through the remainder of the weekend for
Mainland Alaska. Expecting some sea effect snow showers along the
coast this evening before wind direction and temperatures aloft
associated with building high pressure help bring and end to these
showers. A shortwave trough will race across the northwest part of
the state this afternoon. This feature combined with the existing
broad low pressure in the high Arctic will allow light snow to
continue tonight for the western Brooks range and the upper
Kobuk/Noatak valleys with an additional inch of accumulation
expected. High pressure looks to bring precipitation free
conditions for most locations through Sunday. The first of a
series of low pressure systems will move up the western Bering Sea
tonight at around 972 to 976 mb. This will being to increase the
pressure gradient over the central Bering and St Lawrence Island
beginning this evening. A weakening weather front will cross the
central Bering Sunday night and move onto the West Coast on
Monday, with low chances of rain and snow.

A second area of low pressure at around 968 to 973 mb (depending
on the model) will follow the same path as the first, further
helping to tighten up the pressure gradient on Monday with
strengthening gale force winds. A second piece of energy aloft
will cause another area of low pressure to develop near the
Aleutian chain, with rapid intensification as it swings northward
into the northwest Bering Sea ultimately merging with the second
low near the Gulf of Anadyr as a sub 950 mb low. As the third low
moves west of St Lawrence Island and merges with the previous one
Tuesday, very strong winds will develop over the Bering Sea at
least storm force late Monday night into early Tuesday with seas
around 30 feet. Issued a high wind watch for zone 213 with the
anticipation of sustained winds around 60 mph with higher gusts,
which is supported by boundary layer winds and 925 mb winds in the
GFS/ECMWF/NAM. Strong wind headlines will likely be needed for the
West Coast during this time frame, with the possibility of high
wind headlines here as well as this event approaches. A second
weather front will move across the West Coast Tuesday and Tuesday
night, with periods of rain near the coast and snow likely further
inland for portions of the western interior. Things begin to
settle down somewhat on Wednesday as the low pulls of into
Siberia, but not before the potential for additional storm
systems to move into the Bering Sea later in the week under the
deep cyclonic upper air pattern. For information on surge impacts,
please see the coastal flooding section below.

Interior: 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...model guidance suggest
surge values between 4 to 6 feet above tidal levels for St
Lawrence Island, the southern Seward Peninsula and near the Yukon
Delta. Issued a coastal Flood Watch for zone 213 as confidence
appears to be high enough that surge may cause at least minor
flooding impacts for Gambell, as well as Brevig Mission with this
type of flow regime. Given the more westerly track and fast moving
nature of this system, lesser confidence remains for coastal
flooding over northern Norton Sound and near the Yukon Delta in
zone 214. Waiting for future model runs for more consistency and
confidence on any headlines needed for here. Point Hope and
Kivalina will also needed to be watched Tuesday as south to
southeast winds can create beach erosion problems as well.


Afg watches/warnings/advisories...
high wind watch for akz213.

Coastal Flood Watch for akz213.

Heavy freezing spray warning for pkz245.

Small Craft Advisory for pkz220-pkz225.

Gale Warning for pkz210.


Nts Oct 16

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