Petersburg, Alaska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

169
FXAK67 PAJK 121803
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
1003 AM AKDT Tue Aug 12 2025

.UPDATE...Hydrology update as Suicide Basin is now releasing.
Aviation update for 18Z TAF issuance.

&&

.SHORT TERM...Longwave upper level trough is currently dig south,
dragging any remaining precipitation along with it. Embedded
within the trough at the vorticity maximum, strong WSW flow
streaming directly into Mendenhall Valley in Juneau has lead to
enhanced, terrain induced convective rain showers tonight. Dry, NW
flow aloft has begun to move into the Juneau area, marking the
end of the rain this morning. Comparing this to Lynn Canal, which
is currently experiencing breaks in clouds, shows what is in store
for the rest of the panhandle as this trough continues to move
south. Some low clouds and fog down to one quarter mile are
present along the northern panhandle and NE gulf coast, but are
expected to clear by 10 AM this morning with both solar radiation
and increased northerly winds from rising pressure in Canada.
Needless to say, with the sun`s rising, most of the cloud cover
north of the trough is expected to dissipate, leaving mostly clear
skies and temperatures reaching the upper 60s to low 70s across
the panhandle.

.LONG TERM...For the start of the long term period, high pressure
continues to remain over the eastern Gulf Wednesday morning. This
high pressure will allow for a continued break from the rain
across the panhandle. With partly to mostly cloudy skies,
temperatures will be able to warm up somewhat during the day on
Wednesday.

This break in the clouds will be short though as the clouds move
back in for Thursday ahead of our next system that is expected to
impact the area late Thursday. An upper level trough with
associated low pressure will move SW of Prince of Wales and become
vertically stacked, bringing multiple waves to the southern
panhandle. One change is keeping the northern half of the
panhandle drier with NE Canadian air. That is until enough warm
air advection moves into British Columbia, forming a deformation
band. Then, moisture looks to get wrapped up in the easterly flow
and move over the northern half of the panhandle.

Accumulation amounts continue to look to be on the lighter side
until Friday when heavier precip moves in. This heavier precip
looks to be more focused on the southern panhandle approximately
from Sitka to Kake southward at the moment while places north of
there are expected to stay on the lighter side. Winds are expected
to increase Thursday night into Friday morning as well with most
places along the outer coast seeing winds range from 10 - 20 kt at
the time of writing. Through the Inner Channels, winds could be
up to 10 - 15 kt during this time. This will need to be monitored
as we head into the middle of the week for any potential changes.

&&

.AVIATION.../Update for 18Z TAF issuance/...Dense fog early
Tuesday morning has begun to rise for a majority of locations.
Northern locations are already seeing clearing skies, while
central and southern locations are still clinging on to this low
stratus deck for a little longer. These IFR to MVFR regions will
continue to increase to VFR for the rest of Tuesday, expecting
skies to fully clear out by this afternoon. Winds will remain
lighter through the day, with clear areas increasing up to 10 kts
and dropping down to calm by early Wednesday morning.

As clearing occurs, some locations are expected to develop
widespread fog or low stratus decks Tuesday night through
Wednesday morning. Areas where fog does develop should expect
significantly reduced visibilities and ceilings, both of which
could plummet back to IFR/LIFR for these areas until after sunrise
Wednesday morning, at which point daytime heating will see the
fog lift and dissipate, with dry weather expected through the day
on Wednesday for most areas, though a marine layer may linger for
some time in the morning along the outer coast.

&&

.MARINE...Outside: With rising pressures in the northern and
central gulf, and a trough digging southeast through today, look
for an increase in NW winds, particularly this afternoon and
overnight to a moderate to fresh breeze. With very light SW swell,
expecting wave heights to be maximized this morning and slightly
diminish by this afternoon. Tonight will see a marine layer begin
to develop, bringing low clouds and dropping visibilities down to
one mile, particularly near Cape Spencer.

Inside: With the trough digging south to southeast and a ridge
building north and west of the panhandle, this has lead to a
mostly light to northerly wind pattern for the inside waters for
Tuesday. Several locations look to be impacted with increased
winds as the trough digs, mainly east west channels. Icy Strait
and Cross Sound, in particular, will have increasing winds from a
tightening gradient to 15 to possibly 20 knots later this morning
into this evening. Similarly, eastern Frederick Sound zone just
north of Petersburg and Sumner Strait look to see a brief increase
in westerly winds to a moderate breeze.

&&

.HYDROLOGY...

SUICIDE BASIN HAS BEGUN RELEASING AT THIS TIME.

A flood warning for the release of Suicide Basin has been issued.
USGS laser gauge data from Suicide Basin and Mendenhall Lake
levels indicate a release from the basin has started. A crest is
expected around Wednesday afternoon near record levels of
somewhere between 16.3 and 16.8ft. Review published Flood Warning
for more information.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.

&&

$$

SHORT TERM...NC
LONG TERM...NC/SF
AVIATION...GFS/ZTK
MARINE...NC
HYDROLOGY...ZTK

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