Small Craft Advisory 72, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
403 PM AKST Wed Feb 1 2017

.SHORT TERM...An upper level ridge of high pressure is the driving
force for high clouds across the region today. Most places this
cirrus is thin enough for sunshine to get through for a partly
cloudy feel, while the far northern panhandle is a little
thicker, but still a fair weather day. At the surface an inverted
trough has formed along the inner channels while high pressure
builds of the Yukon. Both of these features will strengthen over
the next 24+ hours for a tighter northerly pressure gradient.
Winds have picked up a few hours earlier than expected through
northern Lynn Canal. Skagway has already gusted to 40mph this
afternoon and expect that to continue or increase slightly
tomorrow. By late tonight downtown Juneau will likely have gusts
to 40mph and 60mph gusts are possible tomorrow afternoon. A
similar increasing trend can be expected through the inside waters
with higher gusts out of interior passes and nearby land areas.

Increased wind speeds through tomorrow and extended them further
south through the inside waters based on the increased trend we've
already seen. Used high-res models to bump those up, then adjusted
gusts up further for select locations.

Other big change was to adjust max/min temperatures down. CAA is
already starting and will be stronger tomorrow. Don't expect too
much heating from the short number of daylight hours. Went below
MOS guidance and used more of what we've seen today for starting
values then adjusted wind sheltered locations down and windy spots
up to have about a 10 degree difference for lows. Forecast
confidence is above average.

.LONG TERM...Strong cold air outflow remains the primary concern
for the long range period. Gale force winds expected in many of
the northern inner channels and northern gulf starting Thu night
and continuing into the weekend. Some areas of min storm force are
also possible particularly for Lynn Canal and out of Cross Sound.
Another Taku wind event is also possible for the downtown Juneau
and Douglas areas starting Thu night and continuing into Sat.
Cross barrier flow will be increasing to around 60 to 70 kt with a
noticeable inversion present from the cold air streaming into the
area. The critical level is a little questionable due to the
absence of directional shear aloft. However, there is a level of
speed shear (lower speeds) at around 600 to 700 mb that should be
enough of a critical level to produce the mountain wave. High wind
watch continues for the Juneau area from late Thursday afternoon
to Saturday afternoon.

Into early next week the outflow winds will be diminishing but the
dry weather will persist. The blocking upper ridge to our west
will be retrograding on Monday while a cut off upper low will sit
SW of Haida Gwaii. The panhandle will be stuck under offshore flow
into at least mid week. At that point a trough from the north and
a ridge from the south will reestablish onshore flow over the
area. the question is whether this pattern shift will be enough to
draw a front north into the panhandle by late next week. For now
forecast confidence is rather low so kept chance pops and mostly
cloudy skies for the mid to late next week period.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Watch from Thursday afternoon through Saturday
     afternoon for AKZ025.
     Strong Wind from late tonight through Thursday afternoon for
     AKZ025.
     Strong Wind from Thursday morning through Thursday afternoon for
     AKZ022.
     Strong Wind through Thursday afternoon for AKZ018.
MARINE...Gale Warning for PKZ012-022-043-051.
     Small Craft Advisory for PKZ011-013-021-031>034-042.
     Small Craft Advisory due to Seas for PKZ041.
&&

Ferrin/EAL

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