Gale Warning 92, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
300 PM AKDT Sat Mar 28 2020

.SHORT TERM.../Saturday evening through Monday/ The main focus
over the next few days will be the northerly outflow event
persisting across the Northern Panhandle while light rain and snow
fall in the southern portion of the region. At the surface, an
area of high pressure will remain over NW Canada and a low in the
central Gulf will track SE toward Haida Gwaii.

Outflow winds will increase Saturday night through Sunday from
north to south. The peak of the event is expected to occur late
Sunday night through early Monday morning as the pressure
gradient will be the strongest during this time frame. Gale force
winds in Lynn Canal will increase through the day Sunday possibly
reaching storm force by late Sunday night. Gales are expected to
flow out of cross sound and interior passes into the coastal
waters. SCA winds are expected further south in the central Inner
Channels.

Strong wind headlines are out for Downtown Juneau and Tenakee
Springs for Sunday where gusts over 40 mph are likely. Thinking
the strongest winds in Downtown Juneau will occur Sunday night to
Monday where gusts over 50 mph are possible. There is mountain
wave potential late Sunday night as cross barrier flow is strong
and an inversion sets up above the ridge top. Models are hinting
at a critical level setting up during this time frame as well;
however guidance is suggesting conditions will only remain
marginal for mountain wave development. Have decided not to
increase winds to watch criteria for downtown Juneau; however this
time frame will need to be watched closely. The Klondike Highway
will be another windy location that bares watching as low
temperatures and strong winds will create windchill well below
zero. Decided to issue a windchill advisory for White Pass late
tonight through Sunday morning for windchill values dipping below
-30.

On a positive note, dry downsloping winds will keep precipitation
and low clouds out of the northern Panhandle through the weekend.
Sun shining through breaks in the clouds will be very deceiving
though as temperatures will remain well below average for this
time of year.

As the outflow event persists across the north, light
precipitation will overspread the southern Panhandle Sunday
morning as the low in the Gulf passes by to the SW. Due to outflow
winds slowly bringing the dry air southward during this time
frame, the precipitation with this next system is expected to stay
further south as well. Chance for precip extends as far north as
Wrangell, Petersburg, and Angoon; however kept highest PoP around
POW Island, Ketchikan and Misty Fjords. P-type may start out as a
mixed bag across the southern Panhandle as thickness values will
be right around 1290 and temperature will have had a chance to
cool some overnight. Minor accumulations, if any possible, before
a changeover to rain occurs in the morning as winds shift around
to the SE.

Overall, no significant changes were made to the short term
forecast. Slightly increased temperatures across the north in
areas that remain windy. Wind sheltered areas should be able to
cool off a bit more at night. Used hi-res models to capture areas
of outflow over the water. Confidence is average for the short
term forecast.

.LONG TERM.../Monday through Saturday night/...As of 10 pm
Friday...Anomalous upper-level high centered across northeast
mainland Alaska early next week will displace arctic air southward
with temperatures well below normal through mid week. Ensembles
show a general consensus that the upper ridge should gradually
weaken as it shifts eastward through the middle of next week,
eventually breaking down the strong arctic connection and allowing
temperatures to begin slowly warming. Strong outflow winds and
drying conditions continue Monday due to tight pressure gradient
between arctic high over the Yukon and residual low near Haida
Gwaii. Winds gradually weaken through Tuesday as the high shifts
east and the low dissipates. Later in the week with the return to
more seasonable temperatures likely see low pressure systems
return to the gulf.

Computer models don't like blocking ridges. Mainly with respect to
timing of the blocking ridge break down or shift in location and
how upstream waves will react. This pattern seems to be no
different due to the fact model spread is rather large as early as
Tuesday evening. Continued to use a blend of GFS/ECMWF for Monday
with a transition to WPC for rest of the week. Forecast
confidence is low, expect changes.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind through late tonight for AKZ018.
MARINE...Gale Warning for PKZ012-013-022-043-051-053.
     Small Craft Advisory for PKZ011-021-031-041-042-052.

&&

CM/PRB

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