Heavy Snow in Alaska, December 14, 2023

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
640 PM AKST Wed Dec 13 2023

.UPDATE...Conditionally unstable atmosphere still being moved on
shore, and in isolated circumstances is sparking isolated
thunderstorms near the coast when it interacts with the terrain.
The southern coastline portion should only see these through
about 9 pm and then remainder of the coastline to about midnight.
Incoming system and warm advection is expected to limit that
develop, and switch everything back to stratiform rain as the low
moves into the eastern gulf.

&&

.PREV DISCUSSION....ISSUED AT 248 pm AKST  Wed Dec 13...

.SHORT TERM...Storm force front moves into the AK Gulf this
evening with increasing marine and land winds, building seas, and
heavy precipitation. Models still not in great agreement on this
systems track and have shifted from previous runs. Precip will be
a mix of rain and snow initially due to some pockets of cooler
air at the surface and aloft. Temps drop early Thursday morning
then rise with increasing snow levels through the day with precip
falling as mostly rain. The exception being the far northern
panhandle where Haines and Skagway, along with the respective
highways and borders are under a Winter Storm warning tonight
into Thursday night with snow totals of 7 to 24 inches at higher
elevations. The towns should start mixing with rain as snow
levels rise. Elsewhere snow totals of only a few inches expected
before more rain mixes in. Winds gusts with previous model
solutions looked closer to 60 mph but with the selected track
gusts of 40 to 50 mph are more likely. While not as impactful as
the early week storm the winds and precip are still high enough
for increased run off and river rises. Latest GFS has highest
winds and heaviest precip and a track further north.
NAM,ECMWF,HREF, and Canadian all moves the track more to the south
with a faster moving front, lower winds, and heaviest precip over
the central and southern panhandle. Nudged away from the GFS,
which was an outlier, but did not shift too much to the other
models, keeping storm force winds over the gulf.

.LONG TERM.../Friday through Wednesday/...Active weather remains
for the panhandle for the start of the long term period as a low
continues to exit the area. Most of the panhandle should continue
to see a mix of precipitation during Friday. Most places should
not see accumulating snow but there is the possibility of a few
places picking up a few inches of wet snow before it melts off. By
Friday afternoon, a ridge starts to build into the gulf allowing
for a brief break to the area before the unsettled weather
returns. This ridge will allow for winds to shift around to the
northwest in the gulf. This ridge will persist until a low starts
to set up over the western gulf and Kodiak island. Right now the
biggest question is how far west or east is the low. This location
will affect what happens for the panhandle for the weekend.
Current thinking is that the low is far enough to the east that it
is able to bring some minor impacts to the outer coast and NE
gulf coast. If the low does track farther east though, the
associated front with the low will bring impacts to SE AK.
Unfortunately, deterministic and ensemble guidance still has not
locked onto a final solution for this system so it will bear
watching.

Heading into the start of next week, model guidance for ensembles
continues with disagreeing on the exact solution. Some ensembles
such as the GEFS want to develop a high pressure over the Yukon and
have a low track south of the area into BC allowing for an easterly
wind setup. Meanwhile, the EPS continues to show a low moving north
toward Prince William Sound which would allow for stronger gap flow
to develop but would not result in the easterly winds to develop.
Beyond this, ensemble guidance continues with the diverging ideas on
outcomes.

&&

.AVIATION...Marginal visual conditions prevail with periods of
instrument conditions scattered across all of SEAK due to both
CIGs and VSBY. Cloud bases at or below ridge tops. Plenty of
turbulence reported in PIREPS today as well. Lightning observed
all day long along the outer coast and extending inland 30 to 40
miles, but this is expected to diminish in the evening with little
if any thunderstorm activity anticipated for tomorrow. Little to
no change to any of this for tomorrow.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind from midnight AKST tonight through Thursday
     afternoon for AKZ317-327-328-330-332.
     Winter Storm Warning from midnight tonight to 11 PM AKST
     Thursday for AKZ318-319.
     Strong Wind from 3 AM AKST Thursday through Thursday afternoon
     for AKZ323.
     Strong Wind from 6 AM AKST Thursday through Thursday morning for
     AKZ324.
     Strong Wind from 6 AM AKST Thursday through Thursday afternoon
     for AKZ325-329.
MARINE...Storm Warning for PKZ643-662-663.
     Gale Warning for PKZ033-035-036-641-642-644-651-661-664-671.
     Small Craft Advisory for PKZ011>013-021-022-031-032-034-053-652-
     672.

&&

SHORT TERM...PRB
LONG TERM....SF
AVIATION...Fritsch
UPDATE...Bezenek

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Special Weather Statement
National Weather Service Juneau AK
1028 PM AKST Wed Dec 13 2023

AKZ317-320>332-142200-
City and Borough of Yakutat-Glacier Bay-Eastern Chichagof Island-
Cape Fairweather to Lisianski Strait-City and Borough of Sitka-
Admiralty Island-City and Borough of Juneau-Petersburg Borough-
Western Kupreanof Island and Kuiu Island-Prince of Wales Island-
City and Borough of Wrangell-Ketchikan Gateway Borough-
City of Hyder-Annette Island-
Including the cities of Yakutat, Gustavus, Hoonah,
Tenakee Springs, Elfin Cove, Pelican, Sitka, Angoon, Juneau,
Petersburg, Kake, Port Alexander, Craig, Klawock, Hydaburg,
Coffman Cove, Thorne Bay, Wrangell, Ketchikan, Hyder,
and Metlakatla
1028 PM AKST Wed Dec 13 2023

...STORM FORCE FRONT MOVES IN WEDNESDAY NIGHT INTO THURSDAY
NIGHT...

The second in a series of strong fronts moves over the AK Gulf
then into the Panhandle Wednesday night into Thursday night.
While this fast moving system will bring in periods of heavy
precipitation and strong winds, it is not expected to be as severe
as the system that impacted the region Tuesday.

Precipitation will move in from west to east. Rainfall totals of
1 to 3 inches through Thursday night expected. Highest amounts
along the Eastern Gulf Coast and Central Inner Channels. While
snow will mix in with rain at times, accumulated snow limited to
a few inches. Since rivers and stream levels were elevated from
previous heavy rain, the additional rainfall will not take as
long to bring these waterways to near bankful, however no
flooding expected at this time. Southerly wind gusts peaking at 40
to 50 mph also expected late Wednesday night into Thursday
evening.

Stay tuned to the National Weather Service for updates at
weather.gov/Juneau.