Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 201058
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
258 AM AKDT Sat Jul 20 2019

.DISCUSSION...

Synopsis...
A rapidly deepening low pressure system will traverse the North
Slope today, resulting in wind gusts up to 40 mph in the Brooks
Range passes and wind gusts in excess of 50 mph this afternoon and
evening east of Deadhorse. Wind gusts of 60 mph possible near
Barter Island. Additional rainfall amounts of one quarter to one
half inch across much of the North Slope today, and one half to
one inch possible across the Brooks Range.

Elevated surf is possible for the southwest facing shorelines on
St Lawrence Island, Diomede and Chukchi Sea coast south of Point
Hope Sunday and Monday as the pressure gradient strengthens
between an area of low pressure over Siberia and high pressure
over Western Alaska.

Aloft, at 500 mb, a 520 dam low is located in the high Arctic,
with a shortwave extending southwest across the western Beaufort
Sea and into the Chukchi Sea. This shortwave will quickly move
east across the Arctic Coast today and move over Banks Island
Saturday night. The parent low will slide eastward and waken
through the weekend and early next week. A 562 dam low in the
southern Gulf of Alaska this morning will meander around the Gulf
of Alaska through the next several days, while a ridge axis
extends north into the southern Bering Sea from the north Pacific.
The ridge axis will build north and east across Alaska Sunday and
Monday, becoming centered along the Alcan border Tuesday.

Surface...
A 1003 mb low over the Western Brooks Range this morning will
quickly deepen as it lifts northeast today to be a 998 mb low
near Nuiqsut later this morning, continuing northeast this
afternoon to be a 998 mb low 75 nm north of Kaktovik this
afternoon, and a 998 mb low over Banks Island by early Sunday
morning. High pressure will build eastward behind the low Saturday
evening and night across the North Slope. A weather front will
push across the West Coast and the Interior today, with another
weather front pushing across the North Slope Sunday. High pressure
will build northeast across the Interior Sunday into Monday.

Models...00Z model suite initialized well against the 00Z RAOBS
and the 00Z surface obs. Models are in good agreement with the
overall synoptic pattern through Tuesday, at which point
solutions begin to diverge. At the mesoscale level though,
differences are apparent in the near term. 00Z model solutions
differ in the exact timing and placement of the rapidly deepening
low moving across the North Slope today, with the NAM moving the
low the furthest north and the ECMWF being the slowest. The
differences in the track and timing will make the exact placement
of the strongest winds on the eastern Arctic Coast difficult.
Model convective indices show limited instability today, primarily
along a line from Dot Lake to Chicken and east.

North Slope and Brooks Range: A rapidly deepening low will move
across the North Slope today and over the Beaufort Sea by this
evening, bringing strong winds and rainfall. In the Brooks Range
passes, southwest winds of 20 to 30 mph with gusts to 40 mph are
expected this morning, continuing into this afternoon. As the low
moves northeast, west winds will increase to 20 to 35 mph with
gusts to 50 mph mainly east of Nuiqsut this afternoon and evening,
with 60 mph possible near Barter Island. Upgraded the High Wind
Watch for zone 204 to a High Wind Warning for wind gusts to 60
mph. Strong wind headlines remain in place for zones 203, 205, and
206. Rainfall will accompany the low. Additional rainfall amounts
of one quarter to one half inch across much of the North Slope
today, and one half to one inch possible across the Brooks Range.
On Sunday, another weather front will push across the North
Slope, bringing another round of rain to the region. Temperatures
warming Sunday and Monday.

West Coast and Western Interior: A weather front moving across the
West Coast and Western Interior today will bring more rain to the
region, with the best rain chances occurring along a line from
Unalakleet to Galena and north. Heaviest rainfall amounts will be
north of a Kotzebue to Ambler line, with amounts ranging from a
quarter of an inch to half an inch, with isolated higher amounts
in the favored upslope areas. Elsewhere rainfall amounts will
generally be a tenth of an inch or less. On Sunday and
continuing into Monday, the pressure gradient tightens across
over the Bering and Chukchi Seas, resulting in southwest winds of
20 to 30 mph. Latest guidance suggest that this will lead to
elevated surf for southwest facing shorelines on St Lawrence
Island, Diomede and Chukchi Sea coast south of Point Hope Sunday
and Monday. At this time, coastal flooding is not anticipated.
Temperatures warming Sunday and Monday.

Central and Eastern Interior: A weather front moving across the
Interior today will bring increased southwesterly winds.
Southwest winds of 10 to 20 mph are expected during the day, with
gusts up to 25 mph possible across the Yukon Flats. This could
bring additional smoke to communities in the Yukon Flats. As the
front moves eastward it will bring scattered to widespread showers
from the Upper Koyukuk Valley to the Southeastern Brooks Range,
with isolated showers elsewhere. Isolated thunderstorms possible
this afternoon mainly east of a line from Dot Lake to Chicken.
Warmer and drier conditions expected Sunday and Monday as high
pressure builds in. Temperatures start an upwards trend on Sunday,
with temperatures in the 80s once again making an appearance by
Monday.

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

&&

.FIRE WEATHER...
A deepening surface low moving across the Brooks Range and North
Slope today will bring gusty west to southwesterly winds,
especially north of the Yukon River. Minimum relative humidity
levels are expected to remain above 35 percent and temperatures
are expected to be in the mid 70s in the warmest locations in the
Yukon Flats to near Eagle. A weather front pushing east across
the West Coast and Interior today will bring showers with it. The
best wetting rain chances are along a line from the Seward
Peninsula to Coldfoot and north, with most of the shower activity
south of there expected to be more isolated in nature.
Thunderstorm activity limited today to a line from Dot Lake to
Chicken and east this afternoon.

The area of most concern, the Yukon Flats, will see slightly
cooler temperatures today, with highs in the upper 60s to mid 70s
and minimum relative humidity values in the upper 30s. Conditions
will remain somewhat dry as the area is not expected to receive
wetting rains.

As ridging aloft builds in Sunday and Monday, a warming trend will
ensue, with highs in the upper 70s and lower 80s returning to the
Interior by Monday.

&&

.HYDROLOGY...
A quarter of an inch to one inch of rainfall is expected across
much of the North Slope and the Brooks Range through Sunday as a
series of systems move through the area. This will cause some
minor rises in rivers that drain the Brooks Range.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
High Wind Warning for AKZ204.

Small Craft Advisory for PKZ210-PKZ210-PKZ215-PKZ220-PKZ225-
PKZ235.

Gale Warning for PKZ240-PKZ245.
&&

$$

JUL 19



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