Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 292312
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
312 PM AKDT THU SEP 29 2016
.SHORT TERM...Clear skies and locally windy is the forecast
for Thursday night and Friday. Building high pressure over the
Alaskan interior and northwest Canada is increasing winds out of
interior river valleys and passes. Lynn Canal will increase to
gale force tonight and early friday morning. The gusty winds will
mainly impact the northern inner channels and out of cross sound
of the forecast area. Expecting a Taku Mountain wave to develop in
the downtown Juneau and Douglas Island region tonight. Therefore
have issued a High Wind Warning for the expected winds. The
sustained winds should be 30 to 40 mph with gusts of 60 to 70 mph
possible into Friday morning and improving through the afternoon.
An upper level trough driving south over northwest Canada and the
panhandle may push a few showers into the Misty Fjords area on
Friday out of British Columbia. Accumulations of rain are
expected to be light.
.LONG TERM.../Friday night through Thursday/ Outflow winds will
be on the downward trend in the beginning of the long range. Short
wave that brought the tighter pressure gradients across the north
will have moved south taking some of the winds with it. Outflow
will still be there as cold air continues to spill over the
mountains but that will gradually diminish into Sat as the cold
air mass in Canada moves off to the east.
Farther out several changes in the long range forecast mainly for
early to mid next week as models continue to struggle with the
break up of the upstream ridge. Model trends over the last few
days have continued to show a piece of energy breaking off from a
low in the Bering Sea late weekend and then spinning up its own
low in the southern gulf by early next week. Where it goes from
there has multiple possibilities ranging from a plunge to the SE
toward Vancouver Island to it stalling in the SE gulf tue morning
and lingering near there for much of the rest of the week. Recent
model trends and ensemble guidance are favoring the more
northward track to near Haida Gwaii with the associated frontal
bands moving through the southern half of the panhandle starting
as early as Monday. Forecasts are also trending stronger with
central pressures dropping into the 980s with possible gale force
winds around some of the frontal bands.
The resulting forecast brings rain back as early as mon for the
southern panhandle at least with winds across the gulf and
southern panhandle also increasing. Many areas in the gulf are now
forecast to see 25 to 30 kt winds with some areas of the central
gulf possibly seeing gales Sun night into Mon as this stronger
system moves through. forecast confidence is is still average as
models continue to refine track and strength of the system. Used
GFS and ECMWF before gradually transitioning to WPC for updates to
.AVIATION...With the drier weather, not anticipating any fog
issues at the TAF sites overnight and early Friday. Gusty winds
for Skagway, Haines and Juneau for surface with with Wind shear
for those areas plus Gustavus and Sitka and Yakutat Thursday night
and Friday at times. Turbulence near rough terrain will be common
for much of the forecast area into Friday afternoon.
PUBLIC...High Wind Warning from 1 AM to 4 PM AKDT Friday for AKZ025.
MARINE...Gale Warning for PKZ012-022-042-043-051.
Small Craft Advisory for PKZ011-013-021-031>034-041.
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