Small Craft Advisory 11, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
601 AM AKST Fri Jan 6 2017

.SHORT TERM...Surface analysis and satellite imagery indicate low
pressure over Dixon entrance with a surface trough extending NW
across the Gulf. The main focus through Saturday remains the outflow
winds. The first strong push of cold air is advecting in the wake
of the surface trough as high pressure in Canada strengthens.
Winds already increasing over the northern panhandle early this
morning with storm force winds already occurring over Lynn Canal
and high elevation sites, such as Camp 18 and Sheep Mt gusting to
70-85 mph. These winds will strengthen slightly this afternoon/evening
and continue into tomorrow with strongest winds in favored outflow
areas. Maintained high wind warnings for AKZ017-025. For the
Yakutat area, winds will impact mainly for the passes east of
town. Meanwhile, Taku winds around Juneau will result in gusts to
60-80mph for downtown and Douglas. Cross barrier remains 60-80 kts
this afternoon and there is an inversion above ridge top. Critical
level is not ideal fairly uniform NEly flow, but models continue
to suggest weaker flow in the mid-levels. Think this will be
sufficient to induce a critical level and strong gusts. Increasing
outflow winds will impact much of the rest of SE AK and strong
wind headlines continue for most of the northern and central
panhandle.

As far as precip, expect most of SE to remain dry, but weak
impulses rotating around the low will maintain ISOLD-SCT SHSN
over the southern panhandle with some upslope precip possibly
spilling over from Canada. Any precip is expected to be light with
only an inch or two expected over the southern panhandle.

Forecast confidence remains good and changes limited to local
effects using mostly NAM for guidance.

.LONG TERM...The biggest change for Saturday into Sunday was to
cut the High Wind Warning for Yakutat to 3 PM Saturday. The
tightest gradients begin to relax Saturday afternoon and while
there will be gusty strong winds out of the passes, we no longer
expect any destructive gusts. Yakutat itself will not be afflicted
by any of these winds, although there could be some higher gusts
to 30 mph through Saturday afternoon. The High Wind Warning
through Sunday afternoon for Downtown Juneau still looks
reasonable at this time for gusts of 60 to 80 mph with strongest
winds Friday night into Saturday.

Now as the gradient remains extraordinarily tight across the Coast
Mountains into late Sunday, and the very cold air mass gripped to
Southeast Alaska, we have extended the winter weather advisory for
White Pass through Monday morning for wind chills to 40 below
zero. Snow passing across the pass today and reports from the pass
may dictate whether visibility persists as an issue through early
Monday.

The other change was to continue the trend of pulling away the
snow shower activity across the southern areas. It now appears
that showers will exit midday Saturday.

Breezy conditions will persist across favored outflow areas across
Southeast through at least early Sunday outside of the Klondike
Highway and Downtown Juneau/Douglas but the forecast well
represents this, so very little change was need through the
weekend.

Storm to gale force northerlies and easterlies remain decent. We
did fine-tune some forecasts in Frederick Sound and Clarence
Strait to account for stronger winds outside of passes and we
turned Clarence Strait generally northeast to account for this
into Monday. More fully developed seas look likely through even
Tuesday.

The extended forecast remains mainly clear and cold for the entire
Panhandle. The next weather maker potentially will be some sort
of lee-side low developing in the northern gulf potentially
spreading snow late in the week, but there is such low
predictability given this pattern, that we have trouble changing
the forecast at this time.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning until 3 PM AKST Sunday for AKZ025.
     STRONG WIND through Saturday afternoon for AKZ019-020-022.
     Winter Weather Advisory from 6 PM this evening to 10 AM AKST
     Monday for AKZ018.
     STRONG WIND through this afternoon for AKZ018.
     High Wind Warning until 3 PM AKST Saturday for AKZ017.
MARINE...Heavy Freezing Spray Warning for PKZ022-035-043-051.
     Heavy Freezing Spray Warning for PKZ043.
     Heavy Freezing Spray Warning for PKZ011>013-021-022-031-032-034-
     035.
     Heavy Freezing Spray Warning for PKZ011>013-031-034.
     Storm Warning for PKZ012-013-022-043-051.
     Gale Warning for PKZ011-021-031-032-034-035-041-042-052-053.
     Small Craft Advisory for PKZ033-036.
&&

BC/JWA

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