Storm Warning 6, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
244 PM AKST Thu Jan 31 2019

.SHORT TERM.../Through Saturday/...An arctic front with deep layer
cold advection is pushing south across SE Alaska, bringing in its
wake clear skies and much colder temperatures, along with very
strong winds across the inner channels. An upper trough over NW
Canada is digging toward the panhandle and will continue to dive
south through Saturday. According to satellite imagery Thursday
afternoon, the arctic front has pushed through the northern
panhandle just north of Angoon. A southern stream trough will
continue to move east across the SE gulf Thursday night before
exiting the area by Friday morning. Rain currently being reported
from Prince of Wales to Ketchikan will gradually diminish
overnight from west to east as the arctic front continues its
southward push.

Main forecast concerns through the next few days will be the cold
air outbreak throughout the panhandle, and northerly outflow
winds, especially across the northern inner channels. Temperatures
will gradually cool tonight through Saturday. Expect temps to be
15-20 degrees below normal by Saturday morning. Across the far
north, wind chills below zero could be a factor in the windier
spots Friday and Saturday nights. A wind chill advisory has been
issued for zone 18 near White Pass for wind chills to -45 F.
Northerly winds have increased quickly behind the front with storm
force winds being reported through Lynn Canal. Expect S Lynn to
push upwards of 65 kt through Friday before gradually diminishing
into the weekend. Gales are expected to continue across the
central inner channels through a similar period, and could reach
storm force out of Cross Sound. With these cold temperatures and
strong winds, locally heavy freezing spray will develop over the
northern channels tonight through Friday night, with some freezing
spray into the central areas. High seas may also build to near 15
ft by the persistent strong N winds in Lynn Canal through N
Chatham Strait. A High Wind Warning has also been issued for the
downtown Juneau and Douglas area starting tonight 06z through
Saturday night. Anticipate a Taku wind event developing Friday
with a good critical layer setting up then.

Model agreement has been quite good, so confidence is above
average in this arctic outflow event. Did not need to make many
changes to the inherited forecast.

.LONG TERM.../Sunday through Thursday as of 10 pm Wednesday/
Cold, windy and dry conditions continue into Sunday with mid level
ridge over the AK gulf and deep arctic air flowing in from
western Canada. A surface low/front does move into the ridge
Saturday night into Sunday but as of now stays well to the west of
the panhandle. This wave will likely bump up outer coast gulf
winds. Strong northerly and outflow winds and freezing spray will
begin to diminish Sunday night into Monday as pressure gradient
weakens. Temps will increase but still be well below freezing.
Next low overing riding surface ridge possible moves into the NE
gulf Sunday night into Monday but large amount of model spread
with this feature. In fact all potential waves upstream of the
gulf ridge are showing large differences between models and from
run to run. GFS most aggressive moving in the next wave. If this
solution is correct could see some good snow with an over running
event, however don't count on it yet. Used a blend of GFS/NAM for
Saturday then transitioned to WPC for the rest of the long range
with some GFS/ECMWF on Sunday. Forecast confidence is below
average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning from 9 PM this evening to 9 PM AKST Saturday
     for AKZ025.
     Strong Wind from midnight AKST tonight through Friday afternoon
     for AKZ019.
     Strong Wind through Friday afternoon for AKZ018.
     Wind Chill Advisory from 6 AM Friday to 9 AM AKST Sunday for
     AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ031.
     Heavy Freezing Spray Warning for PKZ012-013.
     Hurricane Force Wind Warning for PKZ013.
     Storm Warning for PKZ012-022.
     Gale Warning for PKZ021-031>034-043-051-053.
     Small Craft Advisory for PKZ011-035-036-041-042-052.

&&

DDH/PRB

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