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FXAK67 PAJK 202232

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
232 PM AKDT Thu Jul 20 2017

.SYNOPSIS...A high pressure ridge over the panhandle will slowly weaken
through Friday as an upper level low moves across the southern gulf.
A frontal band moves into the southern gulf then southern panhandle
on Friday. The front will track northward over the panhandle Saturday
as the low moves into the southeast gulf.


.SHORT TERM.../Thursday night through Saturday/ Stratus cloud deck
over the panhandle under the high pressure ridge did not
dissipate due to limited mid level flow. Some isolated
showers/sprinkles through the day will last into the evening until
the ridge weakens. Frontal boundary over the central gulf
associated with a surface low currently south of the Aleutians
will progress eastward and re- orientate from N-S to E-W through
Thursday night. With more offshore flow over the central and
northern panhandle finally may see some more clearing on Friday.
As the surface low continues to track east, nearing Haida Gwaii
by Saturday, the front will move northward over the panhandle
with more precip and cloud cover. The front begins to shear apart
as it moves north. Heaviest rainfall occurring over the southern
panhandle Friday night with 6 hour accumulations nearing half an
inch. New models runs lowered pops into early Sunday bit faster as
high pressure ridge rebuilds over the panhandle. Increasing winds
along the front over the southern panhandle into Friday, for now
gusts expected to be less than 30 mph.

NAM/GFS continue to be models of choice. Utilized more SREF for
PoP for coverage of the front and diminishing trend by Sunday.
For winds used more NAMNest which initialized well, especially
with weaker winds over northern inner channels. Forecast
confidence is average.

.LONG TERM...Saturday through Thursday as of 10 pm Wednesday/
Saturday begins with a weather front moving northeastward across
the Panhandle. As time progresses preciptiation spreads northward
Saturday with rain in the forecast for most of the Panhandle by
Saturday afternoon. What begins as rain Saturday will transition
into a diminishing shower regime through early Sunday, with a
clearing likely over the central Panhandle late Saturday night
into Sunday morning.

Behind the system an upper level trough and weak surface ridge
build over the eastern gulf and Panhandle through the middle of
the week. Relatively light zonal winds and low chances of
precipitation are associated with this weather pattern.

Most significant changes in the long term were made to Saturday`s
forecast shifting the low pressure center further northeast in
the Gulf. The NAM was used as primary guidance for Saturday and
mainly WPC was used to handle Sunday and beyond.


.MARINE...Southwest swell with building seas to small craft levels
along the AK gulf coastal waters through tonight. Max small craft
winds along the E-W orientated front Friday with potential of a
narrow band of gales. For now left the gales out. Inner channel
wind directions flipping to the north as pressure gradient
shifts with the advancing low Friday, then a quick shift back by


.AJK Watches/Warnings/Advisories...
MARINE...Small Craft Advisory for PKZ041>043.
     Small Craft Advisory due to Seas for PKZ051-052.




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