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FXAK67 PAJK 041821
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
1021 AM AKDT Thu Sep 4 2025

.UPDATE...Update 18z Aviation section. In addition, expanded Dense
Fog Advisories to several location. A low level mesoscale feature
offshore moving northward looks to keep this marine deck pushing
north. Currently expecting solar radiation to cause enough mixing
in the Icy Strait and southern Lynn Canal area to push this up to
a low cloud deck.


&&

.SHORT TERM...

No major changes to ongoing forecast. High pressure ridge is
keeping the dry weather in place. A low level marine deck is along
the outer coast and into the southern and central inner channels,
and expect the clouds to spread even further north Thursday
night. Patches of fog have developed under some portions of the
marine layer.

.LONG TERM...

Slightly cooler trend, increased cloud cover, and a slight chance of
rain returns to the panhandle.

First, an upper level overview: the retrograded upper level low will
looks to be centered in the central gulf by Friday, which will
ensure the high pressure at the surface will stick around at least
into the early weekend, keeping temperatures elevated. Upstream, a
strong upper level low in the Aleutians looks to enhance the ridging
near Kodiak Island, which in turn looks to push out our central gulf
upper level low further south. By early this weekend, a cold
front looks to push across the northern gulf, associated a
shortwave trough moving eastward in wake of the upper level low
that moved southeast. This will be the main driver of both cloud
cover, increased chances of rain, and cooler temperatures.

For rain, not expecting high chances for rain, as moisture is
expected to below. Therefore, keeping rain chances low (20%-30%
chance), and currently not expecting these to raise any higher.
These chances look to be predominantly in the NE gulf coast and Icy
Strait area down to Frederick Sound.

Beyond the weekend, ensemble consensus is the return to an active
pattern with increased rain and wind. While details are not clear
at this time, fall weather does look to be right around the
corner.

&&

.AVIATION...

The marine layer is beginning to push northward,
bringing LIFR to IFR CIGs and VIS all the way up to Angoon. This
layer will begin to battle the sea breezes already beginning to
develop in Gustavus and Juneau. Said sea breezes are currently
expected to cause turbulent mixing, effectively blocking the
northward expanse of the low cloud deck. Therefore, keeping
Gustavus & Juneau northward as VFR through the day today. Further
in the inner channels, particularly around Petersburg, has mostly
only received parts of the marine layer. As this marine layer is
driven by a mesoscale low in the gulf, mountain will largely
continue to shield Petersburg from the bulk of the low clouds.

Currently expecting Ketchikan to clear sooner, as southerly winds
aloft shift to northwesterly from the departing low pressure to
the north.

Expecting to see a resurgence of a marine layer to the same areas,
but this time including Gustavus and Juneau tonight. Widespread
LIFR CIGs will spread over a majority of the panhandle beginning
early tonight. Expecting the central panhandle, including areas
from Wrangell to Angoon to receive a bulk of the fog, with areas
near Clarence Strait raise to a low cloud deck.

&&

.MARINE...
Outside: Little change from yesterday. High pressure continues to
control our skies here in SE AK. West to Northwest winds for the
northern coastal area of 15 to 20 kt, while south of southern
Baranof Island, wind are a southerly 10 kt. The swell remains out of
the south at 3 ft and 10-16 seconds. These wind waves are being
driven by fresh to strong breezes (17 to 27 knots) out of the NW,
highest winds off the coast of PoW and Cape Fairweather. Wind speeds
look to decrease for the second half of the week as the high
pressure weakens.

Inside: Sea breezes continue to be the primary concern for the inner
channels over the next 48 hours. Reported winds speeds have been
getting up to around 10 to 20 kts in the usual trouble spots, Near
Point Couverden, the tighter spots in Stephen`s Passage, and in
Southern Chatham Strait. Winds should calm down during the overnight
and stay lighter into Thursday morning before picking back up again
for the afternoon. Wind speeds look to decrease for the second half
of the week as the high pressure weakens.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Dense Fog Advisory until 11 AM AKDT this morning for AKZ322-327-
     329-330-332.
MARINE...None.

&&

$$

SHORT TERM...GFS
LONG TERM...NC
AVIATION...NC
MARINE...GFS

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