FXAK67 PAJK 080011

Southeast Alaska Forecast Discussion...CORRECTED
National Weather Service Juneau AK
416 PM AKST Mon Dec 7 2020

.SHORT TERM.../Mon night through Wed night/...There is a chance
of some heavier showers and thunderstorms off of the west-central
Panhandle to very near the Sitka area through the evening hours.
Lightning has been detected in that area throughout the day. There
is support for the lightning based upon the Lifted Index and CAPE
values from the Annette, AK, Whitehorse, YT, CA 12Z soundings, and
model forecast soundings.

Snow is expected to decrease for the Klondike Highway, therefore
the Winter Storm Warning for the area ended at 3 PM AKDT.

Interests near Haines should keep weather aware due to excess
rainfall received from some heavier shower activity, today.

Temperatures begin appreciably to come down after the first half of
the short term forecast period. We brought Panhandle temps down a
bit further, especially toward end, based upon new model guidance
and based upon cold air advection approaching southeast Alaska at
850 mb. The precipitation(PoP and QPF) forecast across the 
Panhandle decreases during this same timeframe. Therefore, any new
wintry precipitation will be of the lighter variety.

Models diverge enough toward the end of the short-term forecast
period in terms of the exact location and strength of the low
that emerges into the south-central Gulf on Wednesday. The big
question with that system is exactly where it will come ashore.
The NAM has it crossing land south of Graham Island, BC. All of
the other models have it making landfall anywhere between the
central Panhandle and the Dixon Entrance. Due to this
disagreement, a blend of the GFS, NAM, EC, and the Canadian was
used to get good mean output that looked meteorologically
realistic.

.LONG TERM...Wed through Sun as of 10 pm Sunday...Model/ensemble
solutions continue to struggle with the extended period. There is
good consensus in the parent low to stay over the W Gulf/E 
Bering, but solutions diverge significantly with waves developing
and traversing the gulf with low placement ranging from N gulf
coast to remaining S of the gulf. There is some agreement on
timing with majority of guidance suggesting a break or easing of
precip Thu before another wave moves into the region. High
pressure is also progged to build S from the Arctic so confidence
increased in shift to Nly winds for the N panhandle late in the
week. This means higher confidence in temps cooling especially
across the N with potential for snow back to sea level for late
week. Although, there are no strong signals on any one wave being
particularly strong at this time, stronger winds generally
accompany these developing lows. Overall forecast confidence is
about average.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Flash Flood Watch through Tuesday afternoon for AKZ019.
         Winter Storm Warning through late tonight for AKZ018.
MARINE...Gale Warning for PKZ052. Small Craft Advisory for
PKZ012-022-031-033-035-041>043-051-053.

&&

$$

JLC/BC

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