Juneau, Alaska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

376
FXAK67 PAJK 202338
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
338 PM AKDT Fri Sep 20 2024

.SHORT TERM...A gale force low has entered the gulf that will
continue to help increase wind speeds with the maximum late tonight.
Offshore gales have already begun and will continue to move over the
panhandle, mainly impacting along the coast and the southern inner
channels. You will notice increases in the other channels through
tonight as strong breezes are expected. After peaking late tonight,
winds will start to diminish through tomorrow afternoon.

As for 24 hour rain amounts, the southern half of the panhandle can
expect 2 to 4 inches with the northern half getting less at 1 to 2
inches. This first impactful Autumn storm will dissipate through
Saturday before the next system arrives Sunday. This will be our
first low of many that will go over the panhandle in the coming
weeks.

.LONG TERM...For rain details see hydrology.

Sunday will be the last quiet moment ahead of a potent low moving
into the western Gulf that will dominate the weather over the
next several days. Expect a wide swath of southwesterly winds to
move across the Gulf as a 978 to 982mb low takes residence near
Cook Inlet, jacking significant wave heights in the Gulf back up
to 15 to 18 ft. Along the northern coast, enhanced easterly
severe-gale force winds will drive fresh short period 16 to 19 ft
seas, with 25ft breaking waves due to shoaling near Kayak Island.
For the inner channels, expect 37 to 43 knots out of Cross sound,
with many passageways seeing 25 to 30 knots of wind. For isolated
areas like northern Lynn and Grand Island near Taku Inlet as an
example, likely to see 40 knots of southerly wind. Simply put,
strong wind forecasted over much of the Panhandle starting late
Sunday into Monday with 15 to 18 ft seas enveloping the Gulf
through Tuesday; SE fresh seas Monday becoming SW swell by
Tuesday. Vessels transiting Dixon Entrance and Clarence can expect
southerly gale force winds, peaking early Monday morning.

As in upper level low settles in over south-central Alaska, it
will continue to steer lows into the Gulf, but the resulting wind
fetch will enhance seas into Dixon and Queen Charlotte Sound with
the northern coast shut off from the more extreme fetch generation
area. With that said, the associated surface low will bring
enhanced easterly winds out of Cross sound, and also near Cape
Suckling, with Kayak Island towards Yakutat likely seeing 11 to 14
ft short period seas later Wednesday into Thursday.

&&

.AVIATION...A gale force front is making its way across the outer
coast this evening. Flight conditions are not overly bad right now
with CIGs between 1000 and 3000 feet with little change expected
until Saturday morning. At that time, CIGs and VSBY expected to
decrease below 1000/3. Prior to then, periodic reductions to VSBY
likely in heavier rain. More impactful will be turbulence
associated with embedded convection as well as mechanical
turbulence associated with strong low level winds. Turbulence and
LLWS will diminish to non-impactful levels by late Saturday
afternoon.

&&

.MARINE...The first two impactful Autumn weather systems will
occur tonight and Sunday night. Both will feature pre-frontal gales
over the eastern Gulf of Alaska. The first system tonight is making
its way toward the panhandle creating gale force winds in the
coastal waters. These winds will continue to move over the panhandle
increasing inner channel winds to strong breezes with gales along
the coast and channel entrances. These winds will weaken Saturday
afternoon as the low move over land. There will a short break for
winds as non-impactful winds occur Saturday afternoon and night
before the next low pressure system Sunday. Winds over the eastern
Gulf will organize out of the southeast on Sunday and intensify to
gale force overnight Sunday. Multiple inner channels will likely see
gales or strong breezes Sunday night going into Monday. These winds
will quickly diminish into Monday.

&&

.HYDROLOGY...
It is becoming more likely that the far southern Panhandle will
be under strong atmospheric river conditions (AR-3) with the
central region experiencing moderate (AR-2) conditions. These
conditions are driven by IVT values near 500 to 750 kg/m/s and a
duration of 24 to 48 hours. Furthermore, the ECMWF Extreme
Forecast Index continues to highlight a shift of tails from model
climate for 48 hours, especially over the entire Coast Range.
Simply put, a long duration heavy rainfall event will impact most
of the Panhandle Monday into Wednesday, with the heaviest rainfall
anticipated Monday into Tuesday. After coordination with the
River Forecast Center, rivers are expected to remain well below
flood stage.

For rainfall ranges, 24 hour values Monday and Tuesday are likely
to be 3 to 5 inches at sea level, with 5 inches based off more
extreme guidance outliers. 3 day totals will likely reach near 8
to 10 inches. Certainly a wet fall storm.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 10 PM AKDT this evening for AKZ323.
     Strong Wind from 7 PM this evening to 1 AM AKDT Saturday for
     AKZ327.
     Strong Wind until 7 PM AKDT this evening for AKZ328.
MARINE...Gale Warning for PKZ022-034>036-641>644-661>664-671.
     Small Craft Advisory for PKZ021-031>033-053-651-652-672.

&&

$$

SHORT TERM...EAB
LONG TERM....AP
AVIATION...Fritsch
HYDROLOGY...AP

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