821
FXAK69 PAFG 222236
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
236 PM AKDT Sat Jun 22 2024

.SYNOPSIS...

Broad upper-level high pressure extending across northern Alaska
will continue to bring warmer than normal temperatures and
thunderstorm activity. High temperatures in the 70s today for the
Eastern and Central Interior reach into the lower 80s Sunday
through at least Tuesday. Isolated to widely scattered
thunderstorms across the Western Interior and along the Brooks
Range today will slowly shift back into the Central and Eastern
Interior over the coming days. Along the West Coast, onshore flow
will contribute to increased fog and stratus through Monday. For
the North Slope, a return to fog and stratus begins Sunday.

&&

.DISCUSSION...

Upper Level Analysis...

An upper-level high is situated over the Western and Central
Interior, with broad ridging otherwise extending across much of
the state, leading to fairly warm and dry conditions for northern
Alaska this afternoon. A weakening shortwave trough remains
nearly stationary over the SE Interior and Yukon, providing
upper-level support for isolated thunderstorms. Out west, a
more potent shortwave extending from the Seward Peninsula to
Southwest Alaska is pushing into the Western Interior with
significant cloud cover and scattered to numerous rain showers.
Additionally, weak troughing continues to slowly sink southward
across the Brooks Range, bringing drier air into the Eastern and
Central Interior.

Surface Analysis...

A thermal trough extends west from Yukon through the far SE
Interior into Southcentral Alaska, with a weak extension northward
into the Western and Central Interior. Weak surface high
pressure extends across the marine areas of the Chukchi and
Bering Seas, driving onshore winds and promoting cooler
temperatures along the North Slope and West Coast. With the
thermal trough over southern Alaska, northeasterly winds extend
across the Eastern Interior, bringing in dry air which has dropped
RHs into the 20s. An elevated unstable air mass moving in off the
Arctic Ocean has brought a reprieve from fog and stratus, instead
providing patchy altostratus/altocumulus which has largely
remained out over the ice covered Arctic Ocean. Warm conditions
with temperatures in the 70s with dew points in the upper 40s to
lower 50s have allowed for the development of isolated to widely
scattered thunderstorms from the Upper Kuskokwim Valley north to
the Brooks Range where conditions have been clearer today east of
the West Coast upper trough.

Central and Eastern Interior...

With the thermal trough axis situated to the south of the Alaska
Range today, northeasterly winds have brought dry air across much
of the Eastern Interior. Along with this dry air, another day
with warm temperatures peaking in the mid to upper 70s is ongoing. Warm
and dry conditions with modest northeasterly flow have increased
smoke production with fires along the Tanana Flats, blowing the
smoke off to the south and west. As high pressure remains over
the Western and Central Interior this weekend, expecting
convective potential to continue to be limited as a result.
Despite generally stable/unfavorable conditions, a much weaker
shortwave trough lingering over the far SE Interior is supporting
some isolated thunderstorms this evening. For Sunday, a shortwave
trough shifting east from the Seward Peninsula will support widely
scattered thunderstorms over the north-central Interior. Thunderstorms
make a return to the Eastern Interior early next week as the upper
trough continues eastward. This will also be aided by the thermal
trough which remains fairly broad but locates over the
northeastern part of the state. This may lead to light
southwesterly winds which could bring smoke back over the
Richardson Highway from Monday onward. High temperatures in the
low 80s also return tomorrow and remain likely through Tuesday as
high pressure shifts back east into Yukon.

West Coast and Western Interior...

Upper-level high pressure centers over the Western Interior
today, leading to another day with high temperatures in the 70s
for the interior valleys of Western Alaska. Warm temperatures and
increased instability will support isolated to widely scattered
thunderstorms this evening across the Western Interior as a
shortwave trough lingers across Western Alaska. An upper-level low
dropping south from the high Arctic will entrain the northern half
of the shortwave, pulling it northeast for Sunday, while the
southern half digs and closes off over Southwest Alaska. This
will lead to a split focus for thunderstorms on Sunday: a northern
focus over the northwestern Interior and a southern one over the
Upper Kuskokwim Valley, with more isolated activity in between.
The upper-level high shifts back over the Eastern Interior as
well, while high pressure builds over the Bering and Chukchi Seas.
This will keep westerly flow bringing in cool, marine air along
the West Coast and increase the potential for stratus/fog through
Monday. Meanwhile, highs remain in the 70s over the Western
Interior. For Tuesday, the upper high intensifies over Yukon,
bringing south to southeasterly flow that spreads warmer
temperatures to the north and west.

North Slope and Brooks Range...

An elevated unstable air mass moving in off the Arctic Ocean will
continue to bring a reprieve from fog and stratus for the North
Slope through Sunday. At the same time, a weakening surface high
along the Arctic coast will mean northeasterly onshore flow
relaxes somewhat this weekend. Tonight, an upper-level low drops
south from the high Arctic, pushing its front to the Arctic coast.
The air mass along and behind the front has exhibited low clouds,
so anticipate a return of fog and stratus to parts of the
coastline as early as Sunday morning. Fog/stratus is likely to
lift or burn off each day, but return at night. Along the Brooks
Range, isolated thunderstorms are likely to develop each day.

Extended Forecast Days 4-7...

The latter half of next week looks to be warm and dry for much of
Interior Alaska and the North Slope as a strong upper-level ridge
looks to establish over Eastern Alaska and Yukon. Temperatures
could hover around 5 to 10 degrees above normal from Wednesday
through next Saturday in the Eastern and Central Interior, with
even larger departures from normal possible on the North Slope.
This will enhance fire weather concerns, especially with the
additional threat of thunderstorms present as a series of
shortwave troughs rides up the western periphery of the ridge. To
the west, a potentially gale-force low lifts into the Bering Sea
mid-week. There is less model support for a continued push
northward compared to yesterday, which suggests lower potential
for an elevated surf threat. Regardless, low pressure over the
Bering/Southwest Alaska will bring increased chances for
precipitation to the West Coast and Western Interior, keeping
temperatures near to slightly above normal.

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

&&

.FIRE WEATHER...

Warm and dry conditions continue this weekend with high temperatures
in the 70s and RHs dipping to between 20 and 30 percent in the
Eastern and Central Interior. Expect a warming trend as high
pressure shifts back east and strengthens heading into next week.
This evening, near red flag conditions are ongoing in portions of
the Eastern Interior where temperatures in the 70s, RHs near 25
percent, and northeasterly winds around 10 mph are coincident in
places. Widely scattered thunderstorm activity focuses over the
Western Interior and Brooks Range this evening, with some isolated
storms over the far SE Interior. This activity will shift into the
Central Interior for Sunday and Monday and into the Eastern
Interior for next week. There is some uncertainty in how dry
conditions will remain over the Eastern Interior that depends on
the strength and placement of the upper level ridge, which leads
to decreased confidence in the coverage and intensity of
thunderstorm activity for Monday and Tuesday. However, generally
expecting some moisture recovery as westerly winds bring moisture
currently located over Western Alaska into the Interior.

&&

.HYDROLOGY...

Recent heavy rains have led to higher water levels along the
Fortymile River, but drier conditions expected over the next
several days will allow water levels to fall this coming week.
Glacial fed rivers may begin to rise as warming temperatures lead
to increased high elevation snowmelt.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...None.
PK...None.
&&

$$

Quesada