Small Craft Advisory 18, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
415 PM AKST Wed Jan 11 2017

.SHORT TERM...Challenging forecast for the next 24+ hours. A low
deck of clouds moved into the central panhandle today and has
caused some flurries on and off most of the day in Pelican and
inland to Angoon. Sitka has warmed enough this afternoon for the
p-type to change to drizzle, but some inland areas on Baranof are
likely seeing snow still. Expect the clouds to continue to spread
across the remainder of the panhandle this evening with the light
snow developing overnight. Currently the low deck of clouds is
warm enough that whatever ice crystals are present will not be
able to grow into large flakes, or may even stay as drizzle (will
have to continue watching for risk of freezing drizzle). Think
that the snow that falls tonight will be very small in size or
needles and thus not accumulate much. Have a maximum accumulation
tonight of up to 2 inches tonight. However, models indicate that
after the precipitation starts this evening, temperatures at
850mb will cool several degrees. As this happens the snow flake
type will likely change to slightly larger flakes and allow for
more accumulation to occur, so have gone with up to 3 inches of
accumulation during the day tomorrow.

The pressure pattern across the region remains light this
afternoon, but low pressure developing over the northern gulf
looks to change that tonight. Expect most places to see a wind
shift to the south tonight. The far northern panhandle including
Haines/Skagway looks to stay more northerly, but light/variable
at times, then shift to the south by Thursday afternoon.

Temperatures were colder today due to the cloud cover and little
mixing. Think that there will be some cooling as the precip starts
this evening since the dewpoints area so low, but then stay fairly
steady overnight. Tomorrow the wind shift to the south will warm
things up closer to the freezing point, but think that the high
will be later than normal.

Used mainly the NAM12 for adjustments to this forecast package.
Forecast confidence in snow amounts is lower than normal.

.LONG TERM...Transitions to active weather pattern progressing
with mid to upper level flow pattern becoming consolidated across
the gulf and into the Southeast Alaska. Expecting first of the
waves out of central Pacific, to be gale force for the marine
areas ushering a pool of warmer air to the panhandle through
Friday. Precipitation likely to begin as overrunning snow then the
panhandle should be moving to more of rain.

The Haines and Hyder areas look like that there were is a
favorable period for snow accumulation, Friday to Saturday, so
have started with a Watch for Heavy Snow. Further model solutions
may be modifying the snow forecasts.

The next system will impact the eastern gulf and Southeast Sunday
to Monday. The extended forecasts from the various model solution
had a similar track it had a larger than normal strength
differences between them, although Southeast Alaska to stay wetter
with onshore flow pattern.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Storm Watch from Friday afternoon through Saturday
     morning for AKZ019-029.
MARINE...None.
&&

Ferrin/Bezenek

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