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FXAK67 PAJK 040032
AFDAJK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
332 PM AKST Sat Dec 3 2016

.SHORT TERM...A complicated and dynamic weather pattern has
brought many changes to the forecast. First, while models never
detected it, a wave of sorts in the atmosphere has enhanced
snowfall with the first deep surge of marine cold air from the
west. Snow levels quickly dropped to the surface this morning
across the gulf coast and rain began to change to snow later in
the morning for Petersburg...Wrangell...Kake...and Juneau. A front
with strong lift began the morning with heavy rain showers across
Juneau and the spine of the Coast Mountains. Colder air with
thicknesses down well below 1290 m infiltrated the area along
with impressive lifted indices of up to 8 C/km. A highly
convective environment yielded 1 to 3 inches of quick snowfalls
across the eastern gulf coast and southern Panhandle. We reacted
with Winter Weather Advisories from Juneau for a convergence zone
due to form this evening with the potential for a messy 2 to 4
inches and from 3 to 8 inches of snowfall from Sitka southeast to
Metlakatla including Ketchikan...Craig...Coffman Cove...Thorne
Bay...and Klawock. This event has the potential of lasting through
the morning hours of Sunday.

Models have been of little additional help but social media,
satellite reports, radar, and webcam images have all greatly
helped with situational awareness and to gauge trends. Multiple
waves will head as far north as Juneau this evening, with the
strongest spreading across the south. Thus, there will likely be
breaks from the snow at times through the advisory period with a
potential break tonight this evening for the south before
revamping up late tonight. Confidence is not high.

The brisk northerlies have just now begun through Skagway, and
Northern Lynn Canal will shift later this evening. We have left
strong winds for White Pass tonight and Skagway tomorrow
afternoon, but confidence is not high for the magnitude. Look for
blowing snow to be an issue late tonight for the Klondike Highway,
but given snow will have shut off, we do not anticipate poor
visibilities. These winds coincide with the strongest cold air
advection which begins late tonight into tomorrow as dry Canadian
air migrates southward and begins to end the snow from the north
to south through tomorrow.

.LONG TERM...Cold air will remain entrenched across Southeast
Alaska through much if not all of the extended range. The main
question remains whether or not any precipitation will be able to
overcome the cold, dry air and lead to an overrunning snow event.
The best chance for this will be over the northeast gulf and
northern panhandle Monday night into Tuesday. However, models
continue to struggle with how far east to bring this system so
confidence is low in any one scenario. The main message for the
long range is below normal temperatures will persist through the
period with temperatures remaining below freezing over the
northern half of the panhandle into next weekend.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Winter Weather Advisory until 9 AM AKST Sunday for AKZ023-
     026>028.
     Winter Weather Advisory until 6 AM AKST Sunday for AKZ025.
     Strong Wind from 3 AM AKST Sunday through Sunday afternoon for
     AKZ018.
MARINE...Gale Warning for PKZ012-022-042-043-051.
     Small Craft Advisory for PKZ011-013-021-031>035-041-052.
     Small Craft Advisory due to Seas for PKZ053.
&&

$$

JWA/TPS

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