Storm Warning 20, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
606 AM AKST Tue Nov 7 2023

.SHORT TERM...Chances of rain continue through the day on
Tuesday, though this will notably enough be the relative lull
before the next major system to impact SE AK. A storm force
system will move the through the Gulf of AK on Tuesday, reaching
the Outer Gulf Coast on Wednesday. Anticipate winds reaching 55
kt sustained in some parts of the maritime areas, with the inner
channels expected to see gales or small craft conditions. For
additional details, see the long term forecast discussion.
Operational guidance is increasingly favoring the development of
a new low along a triple point on the front, which could
potentially result in another surge of storm force winds, though
at this time, exactly where this development occurs is not yet set
in stone. While 1-2 inches of rainfall are expected, the lack of
a true atmospheric river in conjunction with this event will help
reduce flooding concerns. A High Wind Watch is in effect for the
southern panhandle from Wednesday afternoon through Thursday
afternoon. For additional details, see the long term forecast
discussion.

.LONG TERM...Impactful system on the horizon with a significant
marine and land wind threat. From Tuesday into Wednesday, a
developing low off the Aleutians will move into the northern gulf
coast. Alongside this low, a frontal band will move eastward
across the majority of the gulf of Alaska. Upper end gales and up
to 20 foot seas will proceed this front. Going into Wednesday
morning, as the front approaches the panhandle, a barrier jet will
set up along the coastline. Within the jet, winds will increase
to storm force with places between 55 - 60 knots. This is well
supported by 850 mb winds exceeding 80 knots. As the front
traverses the panhandle, winds in the inner channels will also
increase to at least gale force with clarance strait hinting at
the possibility of storm force. Current uncertainties in the
forecast is the EC and NAM hinting at a triple point low spinning
up west of PoW island. If this scenario plays out, it is possible
to see moderate storm force winds for southern Clarence Strait.

Looking at land winds, main concern is the southern panhandle both
with and without the possible triple point low. An unstable
environment in lieu of the strongest winds will help encourage upper
air winds to descend down. Therefore, a high wind watch has been
issued for much of the southern panhandle. That being said, Sitka is
the big question mark. Based on the orientation of the front and how
it crosses onto land, there is not enough evidence to include Sitka
in the watch.

Speaking to any rain concerns, current thought process is that most
of the panhandle will receive 1-2 inches of rainfall, with the
highest amounts aimed at the southern panhandle. Furthermore, snow
levels look to shoot up to around 4000 feet in some areas due to
ample WAA, fueling warm rain processes. In coordination with the
RFC, it was concluded that even with the rising snow levels and
therefore raising temperatures, rivers may hit bankfull but are not
expected to flood.

&&

.AVIATION...VFR ceilings for much of the panhandle, although there
are a few ceilings of 1200 to 3000 feet this morning in the
onshore flow pattern across SE AK. Pockets of rain are forming on
westerly upslope terrain through Tuesday. A warm front associated
with the frontal band is moving into the central gulf Tuesday
night and will increase rain chances over the northeast gulf coast
and the northern panhandle.

&&

.MARINE...For the inner channels, winds start the day largely out
of the S. Continued shortwaves moving through the area will keep
winds largely in the 15 to 20 kt range across many of the inner
channels through most of of the day Tuesday, though occasional
lulls may somewhat lower wind speeds for a few areas. Winds will
surge up to gale force and high end small craft for the inner
channels on Wednesday as a storm force front moves across the
Gulf. The southern channels will experience the strongest winds,
alongside ocean entrances.

For the outer coastal waters, anticipate continuing small craft
conditions for many locations on Tuesday, with winds and
wave heights rapidly increasing Tuesday night, and reaching storm
force on Wednesday as a strong storm force front advances into SE
AK. A widespread swath of sustained winds of 55 kt or higher is
expected - for both the central Gulf and for the outer coastal
waters alike. Winds could approach as high as 60 kt sustained in
some locations, with corresponding higher wind gusts. Wave heights
will reach or exceed 30 ft in many locations, potentially
reaching even higher in some locations. An additional surge of
storm force winds is possible as a new low develops along the
front and races N on Wednesday, though the exact location and
timing of this second system is not yet set in stone.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch from Wednesday afternoon through Thursday
     morning for AKZ328-330-332.
MARINE...Gale Warning for PKZ652-664-671-672.
     Small Craft Advisory for PKZ012-022-033-053-641>644-651-661>663.

&&

SHORT TERM...GFS
LONG TERM....NC
AVIATION...Bezenek

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