277
FXAK69 PAFG 202306
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
306 PM AKDT Thu Jun 20 2024

.SYNOPSIS...

Upper-level ridging extending across northern Alaska will
continue to bring warm temperatures and thunderstorm chances
across portions of the Interior. High temperatures will hover in
the 70s across the Interior through Sunday, with cooler
temperatures along the coast. Isolated to widely scattered
thunderstorms shift from the Eastern Interior this afternoon to
along the Alaska Range and into the Western and Central Interior
for Friday through Sunday. A Dense Smoke Advisory remains in
effect for visibility one mile or less in smoke along the
Richardson Highway between Salcha and Birch Lake until
northeasterly winds develop on Friday. For the North Slope, high
pressure will promote intermittent fog and stratus along the
coast.

&&

.DISCUSSION...

Upper Level Analysis...

A ridge extends northwest from Western Canada,
across Interior Alaska, into the Chukchi Sea, promoting fairly
warm and dry conditions across much of northern Alaska this
afternoon. A potent shortwave trough lifting into Southcentral
Alaska is providing divergence aloft which is supporting widely
scattered thunderstorms over the Eastern Interior. Further north,
a digging trough is slowly traversing southward across the Brooks
Range, bringing drier air aloft over the NE Interior.

Surface Analysis...

A thermal trough extends west from Yukon along and north of the
Alaska Range, displaced slightly southward from the upper-level
ridge. Surface high pressure is present in the Chukchi Sea with a
ridge along the Arctic coast. Between these features, generally
light northeasterly winds have developed across the forecast area.
Some locations in the higher terrain east of Fort Yukon have
observed 15 mph winds, while gap winds through the Brooks Range
have gusted as high as 35 mph. A brief, weak southeasterly wind
brought smoke from the McDonald Fire into Fairbanks this morning,
leading to decreased air quality. A drier air mass moving in off
the Arctic Ocean has aided the midday sun in clearing out stratus
and fog on the North Slope. Warm conditions with temperatures in
the 70s with dew points in the 40s have allowed for the
development of ongoing scattered to widespread rain showers and
widely scattered thunderstorms across much of the Interior.

Central and Eastern Interior...

Temperatures will peak broadly in the mid to upper 70s again this
afternoon/evening across the Central and Eastern Interior.
Temperatures in the Yukon Flats will be somewhat cooler than
yesterday as a trough dipping slowly across the Brooks Range
brings cooler air southward. Widely scattered thunderstorms
continue this evening primarily over the high terrain of the White
Mountains, Fortymile Country, the northern foothills of the
Alaska Range, as well as portions of the Central Interior. More
isolated thunderstorm activity is ongoing along the south side of
the Brooks Range. There is potential for thunderstorms to drift
slowly off the high terrain this evening into the Tanana Valley.
Increased mid-level moisture brought by a series of troughs
lifting into the SE Interior will lead to the potential of heavy
rain in localized areas from showers and thunderstorms. Rainfall
totals of half an inch up to one inch per hour will be possible in
localized areas. This could contribute to rapid rises on creeks
in steep terrain along the Alaska Range and in the Goodpaster,
Upper Charlie, and Upper Fortymile River Basins.

High pressure along the Arctic coast has brought a shift to
northeasterly winds in the Yukon Flats today, and northeasterly
flow will spread across the rest of the Central and Eastern
Interior tonight into Friday. Wind gusts up to 25 mph remain
possible this evening and Friday in the higher terrain east of
Fort Yukon. Dense smoke in the Harding Lake area will begin to
clear out along the Richardson Highway as northeast winds develop
Fri afternoon and continue through Saturday.

The upper-level trough digs south of the Brooks Range into the
Eastern Interior on Friday, pinching off the ridge and relegating
the best thunderstorm potential to a corridor along and just north
of the Alaska Range, with some isolated storms remaining possible
in the Central Interior. The pattern remains similar into the
weekend, though convective potential looks to be even lower as the
thermal trough dips south of the Alaska Range and drier air moves
in.

West Coast and Western Interior...

With the upper-level ridge now extending across the NW Interior,
high temperatures in the 70s are expected across much of the
Western Interior, including the Kobuk and Noatak Valleys, as well
as interior valleys of the Seward Peninsula. Warm temperatures
continue through at least Sunday. Warmer temperatures and
increased instability will support isolated to widely scattered
thunderstorms each day across the Western Interior as the upper
level ridge is pinched off to the east and centers over Western
Alaska. At the surface, a ridge builds into the northern Bering
Sea this weekend, promoting stronger westerly flow along the
coast. This will increase the potential for stratus/fog on the
West Coast for Saturday and Sunday and contribute to more moderate
temperatures.

North Slope and Brooks Range...

High pressure along the Arctic coast will keep northwesterly
winds blowing onshore, keeping stratus and fog a persistent
feature along the coast each night. During the day, the greatest
solar heating during midday will help lift fog and clear the
skies. Isolated thunderstorms are likely to develop each day along
the south side of the Brooks Range. High pressure along the coast
will weaken this weekend, causing onshore winds to diminish as an
upper-level low moves in to take its place by Sunday. A front may
begin to move in off the Arctic on Sunday, bringing increased
chances of rain and snow to the North Slope.

Extended Forecast Days 4-7...

Generally expecting continued warmer and drier than average
conditions for the first half of next week, with ridging over
southern Alaska, leading to continued fire weather concerns and
thunderstorm potential across Interior Alaska. There is increased
model agreement with an upper-level low lingering somewhere along
the Arctic coast next week, bringing wetter conditions to the
Brooks Range, with higher precipitation amounts focused in the
eastern half. Uncertainty remains with the placement of this
feature, however, and some model runs, such as the 12z EC, show
limited thunderstorm potential as the upper low advects cooler,
more stable air in from the west and the warmest, most unstable
air is pushed into Yukon and the Northwest Territories, especially
by midweek. A low, potentially gale force, also looks to track
northward through the Bering Sea. For Wednesday and Thursday, its
front lifts along the West Coast, bringing southerly to
southeasterly winds and elevated chances of precipitation for the
West Coast and Western Interior.

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

&&

.FIRE WEATHER...

Temperatures will peak broadly in the 70s across the lower
elevations of the Interior through the weekend, with RHs
generally remaining above 25 percent through Friday. Widely
scattered thunderstorms continue this evening primarily over the
high terrain of the White Mountains, Fortymile Country, the
northern foothills of the Alaska Range, as well as portions of the
Central Interior from Tanana northward. More isolated
thunderstorm activity is ongoing along the south side of the
Brooks Range, and there is potential for thunderstorms to drift
slowly off the high terrain this evening into the Tanana Valley as
well. Increased mid-level moisture brought by a series of troughs
lifting into the SE Interior will lead to the potential of heavy
rain from showers and thunderstorms, leading to increased chances
for wetting rains in the area today and again on Friday.

A shortwave trough dipping south of the Brooks Range will combine
with high pressure along the Arctic coast to bring northeasterly
winds with drier air spreading southward. Gusty winds will be
possible in and around the Yukon Flats, especially over the higher
terrain east of Chalkyitsik, where sustained winds could exceed 15
mph during this afternoon/evening and Friday. Some areas could
approach red flag conditions, though there is increased confidence
in winds remaining below 15 mph at lower elevations where
temperatures may reach 75 degrees, and higher elevations are
likely to be cooler and more moist. As a result, hot, dry, and
windy conditions are not currently expected to coincide.

For Friday, widely scattered thunderstorms will be limited to a
corridor along and just north of the Alaska Range, with some
isolated storms remaining possible in the Western and Central
Interior. As the upper-level trough continues to push south of the
Brooks Range, the thermal trough retreats south of the Alaska
Range for the weekend and drier air spreads across the Interior.
The Eastern Interior could see RHs drop as low as 20 percent. As a
whole, this weekend will see lower thunderstorm potential focused
primarily in the Western and Central Interior which will sit under
a weak ridge of high pressure.

&&

.HYDROLOGY...

Showers and thunderstorms in the SE Interior may produce heavy
rainfall rates of half an inch, up to one inch per hour in
localized areas. This could contribute to rapid rises on creeks in
steep terrain along the Alaska Range and in the Goodpaster, Upper
Charlie, and Upper Fortymile River Basins this evening and again
on Friday.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Dense Smoke Advisory for AKZ839-840.
PK...Small Craft Advisory for PKZ801-812-858.
&&

$$

Quesada