Small Craft Advisory 563, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
633 AM AKST Sun Nov 12 2017

.SHORT TERM...Forecast remains on track with light precipitation
over the southern panhandle with front and occluded feature about
the surface low for Sunday. Tight pressure gradient this morning
resulting outflow winds from interior passes from Yakutat through
Taku Inlet. Winds will be diminishing mid morning to the evening,
although the winds will be increasing again by Monday morning and
then persisting into mid week. Colder temperatures starting to
filter into the northern panhandle out of Canada.

Late Sunday afternoon a sharp short wave will be moving south
along the east side of high amplitude will spin up a low in the
northern gulf that will deepen to about 995 mb Monday morning
while if moves to be about 400 nm west of Dixon Entrance. Not
much in way of precipitation will develop along this low however
some will, and it may extend towards the coastal area of central
panhandle. The low will join the one that moved north to western
Haida Gwaii early Sunday, and the two lows will likely spin about
each other to bring another low north towards western Dixon
Entrance or at least a band of showers on Tuesday.

Todays forecast issue of the day will likely be timing of the winds
diminishing and restarting today combined with temperatures.

.LONG TERM.../Tuesday through Sunday/...A deep upper trough with a
vertically stacked closed circulation aloft and at the surface
will be located west of Haida Gwaii at the start of this long
range forecast period. Upstream, there will be a sharply defined
upper level ridge. Across the interior and northwestern Canada,
strong surface high pressure will have built in. Net effect of
these features will be a continuation of strong northerly outflow
winds and temperatures well below normal for mid November.

850 mb temperatures will be dipping down to -14C by mid to late
week with the far northern inner channels closer to -20 degrees
C, which represents more than 2 standard deviations below normal.
Followed suit with the trend in the previous long range forecast
by lowering temperatures further using bias corrected AKMOS for
guidance. Based on current model spectrum spread, additional
adjustments down may be necessary.

Second major weather element of note in this long range forecast
period will be sustained strong northerly outflow winds. Gales
will continue for the inner channels from Frederick Sound north
for most of the upcoming week. High end small craft
northeasterlies on Yakutat Bay will increase to gales by mid week.
Elsewhere on the northeast gulf coast east of Yakutat and down to
Cross Sound, northeasterly outflow gales will extend well out into
the gulf...also lasting most of the upcoming week.

With the wind and cold temperatures, there will be areas of
freezing spray over the northern inner channels and blowing snow
over higher elevations.

PoP not much of a concern for this coming week. Southern locations
are most likely spots to see any precipitation, and then only a
chance for anything on Tuesday and then again Thursday night
through Sunday. Precip type on Tuesday, if any occurs will
probably be a rain/snow mix. By the weekend, expect any precip
that does fall to be snow.

&&

.AVIATION...Mainly VFR conditions this morning except for a couple
bands of rain or rain and snow south of frederick Sound. Clear dry
and windy for the northern panhandle with an outflow pattern
there. A low moving northward to western Dixon entrance has a
brisk lower level jet, so Klawock and Ketchikan may have some low
level wind shear.

&&

.MARINE...Northerly outflow from interior passes from Yakutat
east to Taku Inlet and possibly south to the Stikine. Gale force
35 to 40 for Lynn Canal this morning is expected to taper off to
25 kt by afternoon, then increasing again to Gales by Monday.
Higher seas from fully built seas over the southern half of Lynn
Canal to far northern Chatham Strait.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until noon AKST today for AKZ017-025.
     Strong Wind until 3 PM AKST this afternoon for AKZ018.
     Strong Wind from late tonight through late Monday night for
     AKZ018.
MARINE...Gale Warning for PKZ012-013-022-043.
     Small Craft Advisory for PKZ011-021-031>035-041-042-051>053.

&&

Bezenek/Fritsch

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