Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 212224
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
224 PM AKDT Mon Aug 21 2017

.DISCUSSION...Long wave troughing remains centered over mainland
Alaska, with the 21/12Z 500 mb analysis showing little change in
the pattern. The trough pattern consists of a 537 dm low center
located near the High Arctic around 78.2N 162.8W. A short wave
trough extended southwest of this low, with the axis running
through Wrangel Island. The second main upper low around AK was
located in the Gulf, about 300 miles south of Kodiak at 542 dm. A
596 dm high was located in the Pacific near 34N 177W, with ridging
extending north through the Aleutians to the Bering Sea. A trough
of low pressure with a 550 dm low over the Sea of Okhotsk ran
southeast through the southern tip of the Kamchatka Peninsula, to
a 561 dm low located near 43.4N 162.3E. Weak downstream ridging
was seen over the BC Coast, which extended north to a 568 dm high
over the southern Canadian Archipelago.

At the surface, high pressure at 1021 mb was located around 100
miles west of Banks Island, with weak ridging extending to the
west through the northern Beaufort Sea. A 1003 mb low pressure is
crossing the Chukchi Sea, located around 190 miles northwest of
Point Hope. A weather front extended south of this low, running
through Point Hope to Wales to Gambell. Low pressure at 995 mb was
located over the Gulf around 110 miles east of Kodiak, with
another weak 1000 mb low located in the north central Pacific
around 44.3N 163.7E. High pressure was located in between these
two features, with the surface ridge running north through the
Aleutians, extending northwest toward the Kamchatka Peninsula
with another narrow ridge extending northeast through Nunivak
Island to Unalakleet to Ambler.

The 21/12Z deterministic models are in good agreement on the
overall pattern through the upcoming week, with some notable
differences on the larger scale pattern appearing by this weekend.
Overall long wave troughing is expected to persist over the state.
Upper low in the Gulf will slowly drift east, to reach the BC
coast by Wednesday afternoon. A short wave rounding the southern
side of the High Arctic upper low will cross the Chukchi Sea today
and reinforce the short wave trough over northwest Alaska Tuesday
morning. This will effectively work to squash the upper ridging
over the Bering Sea. Additional short waves dropping down the
backside of this newly formed trough from eastern Siberia,
combined with the upper lows around the Kamchatka Peninsula,
merging and moving east across the Aleutian Chain toward Bristol
Bay, will further act to deepen this trough Wednesday. Upper level
ridging becomes established over the western Bering and east
Siberia Wednesday night.

North Slope/Brooks Range: Easterly flow will continue over the
central and eastern Arctic Coast with a 1016 mb area of high
pressure over the eastern Beaufort Sea, which will drift off to
the northeast north of Banks Island by early Tuesday. This will
promote periods of IFR fog and stratus to persist through at
least Tuesday night. A weak surface low will cross the Chukchi Sea
tonight, to be located near Point Hope by early Tuesday morning.
The low will track to around Demarcation Point by late Wednesday
morning, with surface troughing still extending westward through
the Brooks Range. The low and front associated with this feature
will continue to advance east through the North Slope and Brooks
Range tonight, bringing periods of rain or showers to this region
through at least Wednesday. Snow levels will fall as cold air
wraps around the west side of the low, ranging from around 4 to 5
thousand feet west of Anaktuvuk Pass tonight to about 1500 feet by
Wednesday night. Snow levels from Anaktuvuk Pass east will fall
between 3000 to 4000 feet Wednesday night, to 1500 to 2500 feet by
Thursday. Several inches of snowfall are expected over the Brooks
Range by Thursday, including Atigun Pass as snow levels fall
Wednesday night into Thursday.

West Coast/West Interior: Frontal system will continue to push
through the West Coast this evening, and into the west Interior by
later tonight. Periods of rain will accompany this frontal system
from the Seward Peninsula north, with lighter rain/showers south
of the Seward Peninsula. Showers will wrap around the low
circulation over the Chuckchi Sea Coast and western Brooks Range
on Tuesday to persist through Wednesday. Strong northwest winds
to around 30 knots will develop on the backside of the low
pressure system tonight into Tuesday. The strength of the wind
and fetch looks favorable enough for high surf and potential beach
erosion for Shishmaref developing tonight and continuing through
Tuesday, before winds turn to the north and diminish late Tuesday
night. High Surf Advisory runs from the Bering Strait to Cape
Espenberg from midnight tonight until midnight Tuesday night as
waves 6 to 9 feet breaking offshore are expected to runup well
above the normal tide lines. Showers look to diminish in coverage
for the west Interior Tuesday night. However, the break in the
rain- free conditons will be short lived, as surface low will move
through the southern Bering Sea Tuesday and Tuesday night, to
reach Bristol Bay by Thursday morning. This will bring another
round of showers to the southwest Interior and YK Delta Wednesday
night into Thursday.

Central and East Interior: Most of the central and east Interior
look to see low chances of showers this evening and tonight, as
weak ridge of high pressure lingers over the area. The best
chances of showers look to be over the southeast Interior this
afternoon/evening, with numerous showers in the Alaska Range, as
moisture and a bit of instability move north from the surface low
in the Gulf. A weakening weather front moves into the central
Interior Tuesday, helping to refocus an area of light rain or
showers here, to push into the east Interior by Tuesday night into
Wednesday morning. Chances of rainfall will diminish for most of
the Interior by Wednesday night, with the exception of the Alaska
Range as moisture pushes north ahead of another surface low that
will reach Bristol Bay by Thursday morning. Snow levels will fall
to around 4500 feet west of the Parks Highway Wednesday night,
which could lead to some snow mixing in with the rain at times
along the highest elevations of the Denali Park Road. Any snow
accumulation looks to be light at this time.


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

&&

.FIRE WEATHER...No concerns at this time.

&&

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

Small Craft Advisory for PKZ220.

&&

$$

NTS AUG 17


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