497
FXAK67 PAJK 211314
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
514 AM AKDT Sat Sep 21 2024

.SHORT TERM...Diminishing trends into short lived quiet weather
tonight for the AOR leading into Sunday`s strong, wet front.
Strong breezes to near gale winds currently persist from Clarence
Strait up to about Icy Strait, but land wind have largely
diminished to 10-15 mph at a maximum. As surface ridging in the
northern and central panhandle takes hold, winds will continue to
lessen. There may be some holdouts in marine winds, particularly
near Stephen`s Passage, however, most areas will be less than 10
knots by this evening. Similarly for precipitation, as ridging
builds, precipitation will come to a fairly rapid end. As such,
Yakutat will most likely see some sun and increased fog chance
this evening, with less confidence for the northern half of the
panhandle.

.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...

Intermittent IFR to VFR flight conditions and rain overspreading
across this panhandle this morning as a low treks across the eastern
Gulf of Alaska. Anticipating predominate MVFR to VFR flight
conditions to continue through the afternoon with CIGS AoB 3000 to
6000ft and intermittent vsbys down to 4SM within heaviest showers
as low pushes into the central panhandle. Rain chances gradually
come to an end from west to east through 06z. Winds decrease
across the panhandle through late afternoon with sustained winds
up to 10 to 15kts and isolated gusts up to 20kts through early
Saturday morning. Likeliest locations for mechanical turbulence
and LLWS across eastern Gulf coast and interior southern
panhandle, gradually diminishing to non-impactful levels by
Saturday afternoon.

&&

.MARINE...
As our first Fall-like weather system works its way inland
through Saturday morning, expecting a short break in elevated
marine winds through Saturday afternoon and night before a second
impactful low pressure systems moves into the Gulf by Sunday,
bringing yet another round of pre- frontal gales across the
eastern Gulf of Alaska. Anticipating winds over the eastern Gulf
to organize out of the southeast on Sunday and intensify to gale
force Sunday night. Multiple inner channels will likely see gales
or strong breezes Sunday night going into Monday. These winds will
quickly diminish into Monday.

&&

.HYDROLOGY...

Key Point: A long duration heavy rainfall event will impact most
of the area Monday into Wednesday, with the heaviest rainfall
anticipated Monday into Tuesday.

Details: 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...None.
MARINE...Gale Warning for PKZ663-664.
     Small Craft Advisory for PKZ022-031-033>036-053-641>644-651-652-
     661-662-671-672.

&&

$$

SHORT TERM...NC
LONG TERM....AP
AVIATION...NM

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