Small Craft Advisory 89, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
400 PM AKST Thu Feb 9 2017

.SHORT TERM...Challenging forecast over the next 24 hours with
accumulating snow on the way for pretty much all of Southeast
Alaska.

An upper level low currently over the north-central gulf will
become elongated as it approaches the panhandle on Friday morning.
Shower activity will be enhanced with this feature and generate
accumulating snow late tonight into Friday as it crosses the area.
Difficult snow forecast with this system as precipitation will be
showery with the convective environment. Due to what will likely
be variable snow amounts, opted to replace the winter storm watch
with a winter weather advisory across most areas. Additionally,
added winter weather advisories for the central/southern outer
coast and southern inner channels beginning late tonight. While
these areas will transition over to rain first by midday Friday,
expect a period of light to moderate snow late tonight through the
changeover time. Through Friday afternoon a general 2-6 inches is
expected with the lowest amounts across the far northern
panhandle. It should be stressed that confidence in snow amounts
at this time is not the greatest. Accumulating snow will continue
into Friday night and this will be covered in the long term
section below.

Winds will increase over the gulf out of the south and west
through the period. The inner channels will see winds shift to the
south and increase through Friday afternoon but most locations
will remain below small craft advisory.

Used the 12z NAM for updates to the previous forecast.

.LONG TERM...Complex forecast for Friday night and beyond as a
strong storm system pushes warm air into the inner channels this
weekend. Main change from the previous forecast is that there is
much more energy coming out of the northern pacific on Sat forming
a noticeable low that will move into the NE gulf by Sat
afternoon. The increase in short wave energy heading further East
has pushed higher winds on Sunday much further south to the point
that they are south of the panhandle. There is also a little bit
of a break in precip in some cases on Sunday.

Overall forecast is still focused on the warm up that will be
happening over the weekend. Timing of the warm up looks to be much
more certain. The southern panhandle and NE gulf coast will
likely see a change from snow to rain Fri afternoon or night,
the central and northern panhandle will change over Sat morning,
while the northern inner channels and Yakutat will flip Sat
afternoon or evening. Before that point a few inches of snow is
possible for many areas. Winter weather advisories are up for many
areas of the northern 2/3rds of the panhandle Fri night. Snow
amount will likely depend on when change over occurs for various
areas which could result in lower or higher amounts then expected.
Meanwhile the Haines and Skagway areas will likely remain snow
longer and could see significant accumulations Sat and Sat night
as the main moisture plume moves in. Near sea level locations will
likely change to rain on Sat but higher areas like White Pass and
the Haines Highway west of the Chilkat river bridge could see snow
well into Sat night. A winter storm watch remains up for these
areas from Fri evening through Sat night.

Into next week, the forecast remain warm and wet as SW onshore
flow remains dominate. Several low pressure systems are forecast
to move north through the western gulf at this time with their
fronts affecting the panhandle as they come north. Surface
temperatures will remain above freezing during most of this time
so ptype will likely remain rain for all areas except the higher
elevations of the Haines and Klondike Highways and maybe Hyder.
Occasional windy conditions are also possible as these fronts
come through. Forecast confidence is about average for this far
out with the various models still trying to settle on the timing
and structure of the individual systems. Mainly used WPC for
guidance for the extended.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 6 AM Friday to 6 AM AKST Saturday
     for AKZ024-026.
     Winter Weather Advisory from midnight tonight to noon AKST
     Friday for AKZ023-027.
     Winter Weather Advisory from 9 AM Friday to 6 AM AKST Saturday
     for AKZ020-021-025.
     Winter Weather Advisory from 3 AM Friday to 6 AM AKST Saturday
     for AKZ022.
     Winter Storm Watch from Friday evening through late Saturday
     night for AKZ018-019.
     Winter Weather Advisory until 6 AM AKST Saturday for AKZ017.
     Winter Weather Advisory from 3 AM to noon AKST Friday for AKZ028.
MARINE...Small Craft Advisory for PKZ022-036-041>043-051-052.
&&

TPS/EAL

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