Small Craft Advisory 694, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
311 PM AKST Thu Nov 10 2016

.SHORT TERM...Occluded front will be E of the area early this
evening. A low over the S-central gulf will move N to the
N-central gulf by Fri afternoon. A series of vort maxima aloft
will move across the area tonight and Fri. Used the 12z GFS to
tweak winds over the gulf tonight, then Fri forecast was not
changes significantly.

Main concerns will be TSTM potential and winds. There are some
TSTMS occurring along the vort lobes over the E gulf attm, and
they will continue over the gulf through Fri. Trickier part is how
far TSTMS get inland. Given lower levels still mild and fairly
moist, and decent lift will occur with the vort lobes, think the
outer coast and S and central inner channels will see some threat
for TSTMS. Best chances for them will be this evening and Fri,
except mainly this evening for the S and central channels. The
TSTM threat will begin to diminish from the S Fri afternoon as low
moves into the far N gulf and warmer air aloft moves in to the S
gulf.

The main wind threat will be from low moving N through the gulf.
expect gale force winds around this low as it moves N. Inner
channels will see strongest winds late tonight and Fri with 25-35
KT winds likely over much of the area. There will be some leftover
gales early this evening for Clarence Strait and along the far NW
part of the gulf coastal waters. Not going with strong wind
headlines at this point, but gusts could be close especially late
tonight and Fri.

Otherwise, temps will not fall too much tonight given well mixed
airmass persisting, and there will not be much of a rise on Fri.
About the only threat for snow will be near White Pass, and that
will be mainly in the highest part of it. They could get around a
couple inches of snow through Fri though.

.LONG TERM...Active pattern continues with multiple fronts
affecting the panhandle over the coming week. Dry weather looks
promising beginning next Thursday...at least over some locations.
Root cause for this is an upper level jet stream which continues
to steer a series of upper lows into the gulf. As each low fills,
it is replaced by another upper low. Most, if not all, of these
lows are vertically stacked barotropic systems, meaning that the
associated surface low is located very nearly underneath the
corresponding upper feature. Additionally, each system has a
mature front associated with it. Southerly or southeasterly winds
generally will remain at small craft intensity with frequent
periods of gales. Periods of gales on the inside as well with
directions typical for an offshore pattern with deep low pressure
over the gulf.

Warm low level air will be advected in from the south with each of
the fronts, keeping snow levels high enough to prevent snow
anywhere except the higher elevations of the two highways.
Temperatures expected to fall somewhat by mid week next week, but
PoP dries up by then, so chances for snow entering the second half
of November not looking good right now.

Used a NAM/ECMWF blend for pressures Friday night through Sunday
afternoon. Used ECMWF overnight Sunday to Monday afternoon.
Blended EC to existing grids for Monday night, then went with WPC
thereafter. Winds from NAM through Sunday afternoon. Most of the
remainder of the forecast left unchanged. Overall forecast
confidence is average.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...STRONG WIND until 3 PM AKST this afternoon for AKZ027-028.
MARINE...Gale Warning for PKZ031-034>036-041>043-051>053.
     Small Craft Advisory for PKZ011>013-021-022-032-033.
&&

RWT/Fritsch

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