Small Craft Advisory 739, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
310 PM AKST Fri Nov 25 2016

.SHORT TERM...A low over the central Gulf will elongate toward
the southeast through the eastern gulf and weaken overnight.
Strong steering flow from the eastern Aleutians southeast into the
north Pacific has effectively stalled our system in the gulf.
Therefore, we expect southeasterly small craft winds to 25 kt will
continue along the northeast gulf waters. As this system weakens
overnight, southerlies across the bulk of the Inner Channels will
relax overnight and even turn northeast or north late tonight.
However, a stronger shortwave will enter the western gulf tomorrow
and begin to once again turn surface winds southward. This will
usher another round of warming for tomorrow. But wind magnitude
increases will be delayed until Saturday night.

Temperatures have largely behaved as expected: they have climbed
above freezing in many locations as the rain/snow line has both
migrated northward from Petersburg to the Icy Strait corridor
through the day as well as migrated upward in elevation. Two
spots that have kept chillier than expected are Haines and
Yakutat. Chilkat Valley drainage wind still allows freezing air
from across our friendly Canadian borders. We will see little
warming here until tomorrow when winds go east. Yakutat is an
interesting case. We think the orientation of the front may be
aiding a persistent offshore component in their winds. This has
helped chill the column to temperatures sufficient for snow to
survive the fall to the surface. While we still think the
changeover will occur, we have pushed it to 06Z for the rain
changeover with an inch of snow accumulation through 9 pm.

Southerly winds through Lynn Canal tomorrow will begin to push the
rain/snow line to just beyond Haines and Skagway in the afternoon.
Overall, accumulations with this system will be light, for it's
the second system on its way Saturday night and Sunday that will
bring in healthier totals.

Finally, we have added some patchy fog over southern areas to take
into account lighter winds, clearing skies, and a more stable
atmosphere. Some of this fog may spread northward, but right now
we think the clouds will inhibit this.

.LONG TERM...Period begins with the first in a series of storms
impacting the region Sat night into Sun. This gale force low will
result in gales over the gulf and coastal waters along with a
round of precip and breezy winds as it pushes across the region.
Although WAA will prevail ahead of this system, expect
accumulating snow down to sea level for areas in the central and
northern inner channels. Winds will rise to advisory levels over
the inside waters Sat into Sun as well. This active pattern will
persist through the extended with a brief break Sun into Mon
before another strengthening system lifts out of the northern
PacificMon into Tue. This system seems to be the strongest at
this time, but models still depict some spread in the track of
this system, so the exact impacts still difficult to pin down.
Regardless, another round of winds and precip will impact the
region. Models show another system moving into the central gulf
around mid week. Biggest changes to forecast were related to this
system as model solutions over the past 24hr has been further W
and deeper with the low center. Some brief breaks in between
systems expected as short wave ridge follows each front. Given the
quick movement of these systems, it's tough to nail down the exact
timing of diminished precip. Forecast confidence is above average
in the synoptic pattern but decreases significantly regarding
details such as timing and ptype challenges.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ022-034>036-041>043-051-052.
     Small Craft Advisory due to Seas for PKZ053.
&&

JWA/BC

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