Small Craft Advisory 8, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
450 PM AKST Wed Jan 4 2017

.SHORT TERM...Extensive low clouds in the gulf and inner channels
today with ceilings in many places between 500 and 1500 ft. Only
the southern inner channels and the northern extent of Lynn Canal
have remain low cloud free today. Some locations in the central
inner channels have even reported some flurries throughout the day
as a weak shortwave traveled through the panhandle. Where these
low clouds go tonight and what happens with the developing outflow
tomorrow are the main concerns for the next 24 hours.

A developing weak low in the NE gulf tonight that will slide SE
along the coast late tonight into Thursday will determine what
the low clouds do. Current thinking has the low clouds clearing
out from NW to SE as northerly outflow develops in the wake of the
low. However there are some mid to high level clouds that will be
building in late tonight as a vigorous upper level shortwave moves
through. Some flurries could also develop late tonight into early
tomorrow for the central panhandle as that same shortwave squeezes
even more moisture out of the remaining low clouds. So have
included flurries for the central inner channels for early
tomorrow as well as this evening (due to lingering flurries).

Outflow winds will be increasing out of the usual outflow areas
tomorrow as the shortwave draws cold air southeastward into the
southern Yukon. Lynn Canal will have winds increasing to gale
force by Thu afternoon with winds possibly gusting to 40 mph at
Skagway. Decided to issue a strong wind headline for Thu afternoon
as a result. Gale warnings and small craft advisories are also
posted for many of the northern inner channels as well.

Mostly local effect changes for winds and clouds cover for
forecast changes today. The inclusion of flurries was also one of
the changes from the previous package. Mainly used hi-res Nam
boundary layer RH for Sky cover guidance and Nam for other
guidance.

.LONG TERM...The blocking ridge aloft with an axis between 160
and 170 W will hold in place as expected. A short wave on Thursday
will move south into the gulf developing a closed low feature
Friday. This feature will continue to move southward through
Saturday afternoon to be near 50/140. Strong surface high (1050+ mb)
builds into the Alaskan interior and northwest Canada Friday.
A surface low near Haida Gwaii Friday will move slowly south to the
eastern Pacific on Saturday. Expect the strong outflow winds to
increase Thursday and persist into early next week.

Will need to watch for potential mountain wave strong winds
impacting the Juneau area during the weekend.

Precipitation is limited to mainly the southern panhandle through
the end of the week, and then that should even taper off by Sunday.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind Thursday afternoon for AKZ018.
MARINE...Gale Warning for PKZ012-052.
     Small Craft Advisory for PKZ011-013-021-022-031-043-051-053.
     Small Craft Advisory due to Seas for PKZ041.
&&

EAL/Bezenek

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