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643
FXAK67 PAJK 210024
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
324 PM AKST Mon Nov 20 2017

.SHORT TERM.../Through Tuesday night/ An occluded front over the
eastern gulf will move into the northern panhandle tonight, then
slowly weaken there Tue. The arctic front will remain across the
central panhandle through Tue. Did not make any big changes to the
forecast through Tue night, with mostly local effect edits made to
a few spots.

With the occluded front moving onshore tonight, expect overrunning
snow to develop over the N half of the area, with some rain and
snow along the central and southern outer coast. Kept the winter
weather headlines as is, with WWA for zones 20-21-24 and 25. Still
looks like a general 3 to 6 inches of snow in the advisory area.
Snow will be on the fluffy side as well. N and S of the advisory
area, a couple of inches are possible although zones 19 and 22
could get more like 2-4 inches. The snow should taper off Tue
afternoon as occluded front falls apart. More precip may get into
the far S area by late Tue night as another occluded front
approaches from the S.

Still some gale force winds out of Cross Sound into the NE gulf,
and in N Lynn Canal. These winds will slowly diminish tonight into
Tue, but still expect SCA level winds to continue over the N inner
channels and in outflow areas into the NE gulf. S area will have
some SCA level winds tonight that should diminish some Tue.

.LONG TERM /Wednesday through Saturday/ Active weather pattern
continues through the extended forecast. A low looks to approach
from the south early Wednesday with a weakening frontal band
spreading precip north across the region through the afternoon.
With the low to the south, winds through the inner channels will
continue to be out of the north. Many places will have at least
small craft level winds with gale force gusts out of interior
passes. These winds will likely decrease behind the frontal band
for a period.

Model differences on the low approaching from the south on Wednesday
are vast and have been very inconsistent over the last several days.
Interestingly, latest models are in good agreement on warming
temperatures aloft on Wednesday with the 0C line at 850mb reaching
as far north as Juneau. This would mean more of a mix or change over
to rain for many locations that have only seen snow in the last 2
weeks. Since this is a new idea among the models, we have only
increased temperatures slightly during this time with mostly snow
and will adjust further if this warming trend continues with
subsequent model runs. Either way, the frontal band would be
weakening with an offshore component to the wind thus limiting
accumulations to a few inches. However, closer to the low center,
the southern panhandle could see heavy rain.

There is slightly better consensus for another low moving into the
central gulf from the west Thursday night then meandering in the
gulf through next weekend. This is a change from what we were seeing
a couple days ago where a warming trend was looking likely and
moisture coming from the south, now with the low coming across from
the Bering, temps may not warm as much over the holiday. Still have
many places seeing a mix but overall confidence in the rain/snow
line across the central panhandle lowers through the end of the
week.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory from 9 PM this evening to 9 AM AKST
     Tuesday for AKZ024.
     Winter Weather Advisory from 9 PM this evening to noon AKST
     Tuesday for AKZ025.
     Winter Weather Advisory until 9 AM AKST Tuesday for AKZ020-021.
MARINE...Gale Warning for PKZ012-022-043.
     Small Craft Advisory for PKZ013-021-031-032-034>036-041-042-
     051>053.

&&

$$

RWT/Ferrin

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