771
FXAK69 PAFG 192322
AFDAFG

Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
322 PM AKDT Wed Jun 19 2024

.SYNOPSIS...

Upper-level ridging will continue to bring generally warm
temperatures and thunderstorm chances across northern Alaska. High
temperatures will hover in the 70s across the Interior through
Saturday, with cooler temperatures along the coast. Isolated to
widely scattered thunderstorms are expected for the Interior each
afternoon. A Dense Smoke Advisory is in effect for visibility one
mile or less in smoke along the Richardson Highway between Salcha
and Birch Lake. For the North Slope, high pressure will promote
intermittent fog and stratus along the coast.

&&

.DISCUSSION...

Upper Level Analysis...

A closed upper-level low is situated over the Gulf of Anadyr this
afternoon, while broad ridging extends up from Western Canada,
across Interior Alaska, into the Chukchi Sea. A shortwave trough
is dipping southward over the Beaufort Sea on the east side of the
ridge, with a weaker second shortwave lifting along its western
periphery across the Central Interior, aiding the support of
showers and thunderstorms in the area.

Surface Analysis...

A thermal trough extends northwest from Yukon along and south of
the Brooks Range, aligning well with the upper level ridge. Surface
high pressure is present in the Chukchi Sea with a ridge along the
Arctic coast. Winds are generally much lighter across the forecast
area today with the dissipation of the weak low in the Chukchi
Sea. The exception is northeasterly winds which continue across
much of the North Slope, advecting a layer of stratus and fog in
off the ice. Warm conditions with temperatures in the 60s and 70s
with dew points ranging from the 40s into the low 50s have
allowed for the development of ongoing scattered to numerous rain
showers and widely scattered thunderstorms across the Eastern and
Central Interior.

Central and Eastern Interior...

Temperatures will peak broadly in the mid to upper 70s once again
this afternoon, with locations on the Yukon Flats likely seeing
temperatures reach 80 degrees again today. Widely scattered
thunderstorms continue this evening primarily over the high
terrain of the White Mountains and Fortymile Country, with storms
also moving southward off the Central and Eastern Brooks Range.
Elsewhere, isolated thunderstorms are possible. A potent
shortwave lifting into Southcentral Alaska will shift the focus of
convective activity further south for Thursday as another
shortwave trough dips south of the Brooks Range. Expect slightly
cooler temperatures, especially in the Upper Tanana Valley near
Northway as quite a cloudy, wet day looks to shape up. High
pressure builds along the Arctic coast, bringing a shift from
southwesterly to northeasterly winds on Thursday. Some areas in
the Yukon Flats could see winds gust up to 25 mph Thursday,
Friday, and Saturday afternoon/evening. 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 for Saturday, though
convective potential looks to be even lower as the thermal trough
dips south of the Alaska Range.

West Coast and Western Interior...

A cool, stable marine air mass is being drawn up along the
western periphery of the ridge over Interior Alaska, covering much
of the West Coast and Western Interior with stratus and dense
fields of low-topped cumulus this afternoon. This will limit
instability sufficient for thunderstorms to only allow isolated
coverage for portions of the Western Interior today. The upper-low
that had been bounding the upper-level ridge over the past few
days continues westward over Chukotka tonight, allowing the ridge
to extend west. Temperatures warm up, with highs in the 70s
expected for the Kobuk and Noatak Valleys, as well as interior
valleys of the Seward Peninsula beginning tomorrow and continuing
through Saturday. Thunderstorm activity spreads west, with widely
scattered storms expected on Thursday in the Western Interior. The
Western Interior becomes the focus for convective activity by
Friday and Saturday as the upper level ridge is pinched off to the
east and centers over Western Alaska.

North Slope and Brooks Range...

High pressure will remain entrenched along the Arctic coast,
allowing northeasterly onshore flow to persist. This will bring
stratus and fog along and near the coast each night, with the
greatest solar heating during midday contributing to lifting
fog/clearing skies. Isolated to widely scattered thunderstorms are
ongoing along the south side of the Brooks Range this afternoon
and will push southward into the Interior this evening. A digging
upper trough will bring less favorable conditions for
thunderstorms the rest of the week, keeping coverage isolated and
confined primarily to the Brooks Range through Saturday.

Extended Forecast Days 4-7...

A fairly blocky, stagnant pattern is expected with an upper-level
low over the Arctic Ocean looking to drop southward into Northern
Canada for midweek and a ridge, possibly closed off, somewhere
over Western Alaska. As a result, there is potential for the
upper low to bring wetter conditions to the Brooks Range next
week, with the accompanying cooler air mass generally inhibiting
thunderstorm potential for the Eastern Interior. There is
significant uncertainty in the exact placement of features, such
that if the upper low remains over the Arctic Ocean (as the 12z
GFS depicts) instead of dropping south, drier conditions in the
Brooks Range with greater thunderstorm coverage across the
Interior is possible. Otherwise, generally drier and warmer than
average conditions are expected, leading to continued fire
weather concerns.

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 end of the week. RHs
generally remain above 25 percent through Friday. Widely
scattered thunderstorms continue this evening primarily over the
high terrain of the White Mountains and Fortymile Country, with
storms also moving southward off the Central and Eastern Brooks
Range. Elsewhere, isolated thunderstorms are possible. A potent
shortwave lifting into Southcentral Alaska will shift the focus of
convective activity further south and increase moisture over
the Southeast Interior for Thursday. As a result, there will be
increased chances for wetting rains in the area on Thursday, and
to a lesser degree on Friday.

High pressure builds along the Arctic coast, bringing a shift
from southwesterly to northeasterly winds on Thursday. A shortwave
trough dipping south of the Brooks Range at the same time will bring
dry air aloft, which could mix down to the surface with the
combination of warm temperatures and gusty northeasterly winds in
the Yukon Flats. This could potentially drop RHs as low as 20
percent, though it will be dependent on the timing of the
shortwave, which if it arrives later Thursday night, would not
allow for RH to drop that low. Otherwise, some areas could
approach red flag conditions, with temperatures in the 70s, RHs
in the 20s, and northeasterly winds sustained at just below 15
mph. Gusty northeasterly winds continue for the Yukon Flats each
afternoon through Saturday, though some recovery in moisture is
expected.

The upper-level trough digs south of the Brooks Range
into the Eastern Interior on Friday, relegating the best
thunderstorm potential to a corridor along and just north of the
Alaska Range, with some isolated storms remaining possible in the
Western and Central Interior. The pattern remains similar for
Saturday, though convective potential looks to be even lower as
the thermal trough dips south of the Alaska Range. However, RHs
trend slightly downward for Saturday as the digging trough spreads
drier air across the whole of the Interior.

&&

.HYDROLOGY...

River levels on the North Slope continue to fall. The main threat
(though low) is flash flooding with slow moving thunderstorms
across the Eastern Interior today over steep terrain. There is
some increased risk on Thursday and Friday over the SE Interior
and Alaska Range where ample moisture will lead to the potential
for heavy rain-producing thunderstorms.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Dense Smoke Advisory for AKZ840.
PK...Small Craft Advisory for PKZ812.
     Small Craft Advisory for PKZ858.
&&

$$

CQ