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FXAK67 PAJK 240010

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
310 PM AKST Thu Feb 23 2017

.SHORT TERM...An inverted trough of low pressure extending
northward over the inner channels and a ridge of high pressure
over the central gulf are working together to cause a N-NWLY
breeze through the inside waters. Most places have 10-15kt winds
but some down south and those enhanced by sea breezes have been
10-20kt this afternoon. Expect that to continue through most of
the night, then the pressure gradient will start to relax going
into Friday morning.

Skies have become partly cloudy to mostly clear across the area
this afternoon. The little bit of wind going on will help to keep
temps from falling as sharply this evening, but interior
locations with light winds will likely end up being a few degrees
colder than they were this morning. Tomorrow, mostly sunny to
partly cloudy skies will allow for temperatures to rebound
quickly. Temperatures aloft will be warming as well as the ridge
of high pressure shifts E-SE. Will need to keep an eye on the
ridge and its temperature inversion to see if a marine layer
develops over the gulf Friday morning.

Clouds will start increasing over the northern gulf through the
day Friday ahead of a developing low pressure system. This could
introduce some light rain to Yakutat by late afternoon and have
continued with a chance for this forecast package. This system
develops further going into Friday night, see the long term
forecast period.

Used mainly the NAM for updates today. Forecast confidence is
above average.

.LONG TERM...A rapidly moving disturbance will drop southeast over
the panhandle Friday night into Saturday bringing a brief shot of
rain and snow to the area. Any snow accumulations will be limited
by a warm boundary layer due to southerly low level flow and the
quick moving nature of the system. The most noticeable change
will be a rapid transition from southerly to northerly winds as
the system passes. This wind shift will occur late Friday night
over the northern inner channels and late Saturday
morning/Saturday afternoon over the southern inner channels. The
enhanced northerly winds will rapidly diminish on Sunday as the
pressure gradient slackens over the area.

There remains good operational and ensemble model agreement on an
interesting scenario unfolding as we head into early to mid next
week. A potent northern stream shortwave will dig into the
northern gulf, developing a closed upper low and strengthening
surface low. This will set the stage for an overrunning
precipitation event with cold air in place over Southeast Alaska.
This particular synoptic pattern is very favorable for significant
accumulating snow in the panhandle. However, the exact track and
evolution of the northern stream energy and any phasing with the
southern stream will have large impacts on the forecast. With all
that being said, this is a time frame we will be watching closely
over the coming days.

Used the 12z NAM through 84 hours then the latest WPC thereafter.


.AJK Watches/Warnings/Advisories...
MARINE...Small Craft Advisory for PKZ041.
     Small Craft Advisory due to Seas for PKZ042-043.



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