Gale Warning 302, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
253 PM AKST Thu Dec 13 2018

.SHORT TERM.../Through Saturday night/ The gale force low over the
central panhandle is on its way out, but not before it battered
the outer coast with wind. Cape Spencer and Cape Decision both saw
sustained winds well into storm force with gusts as high as 76 kt
(May have been some terrain effects increasing wind speeds there).
Other places like Sitka and Elfin Cove saw brief gusts as high as
48 kt at one point today. This storm also brought some
precipitation to the panhandle with areas from Hoonah and Juneau
northward cold enough to see up to 2 inches of snow today.

Into tonight that storm will continue to move into Canada with any
remaining winds diminishing through the evening. Behind it
showers are the rule of the day. There is an area of enhanced
showers associated with an area of low level vorticity out in the
gulf that is also producing an occasional lightning strike. That
will be moving into the northern panhandle and gulf coast
overnight spreading more showers and possible thunderstorms as it
comes. The result is a persistence of scattered snow and rain
showers (with slight chance of thunder for the outer coast)
through the night before it finally dissipates tomorrow morning.
Where it is cold enough for snow, accumulation expected to be
around 1 to 2 inches or less.

Friday, is expected to be dry but cold as an area of cooler air
and less cloud cover moves in. Temperatures may not get out of
the low to mid 30s for highs, with overnight lows on Fri night
dropping below freezing.

Forecast becomes active again into Sat as a large storm force low
moves into the central gulf. Wide spread storm force winds remain
in the forecast for the gulf with winds in the panhandle increasing
through the day Sat as the associated from moves inland. Precip
will also be returning and with the cold air in place in the
panhandle many places may start as snow for ptype. Some
uncertainty on how long the cold air will hang on before it is
pushed out by the warm air advection from the system and changes
everything over the rain. Which in turn will affect snow
accumulation forecasts. Northern inner channels in particular will
have to be watched as depending on how fast the warm air moves in,
snow totals in a certain area could range from nothing to a few
inches.

Forecast confidence is moderate to high as guidance is in good
agreement today. Gfs and Nam mainly used for guidance.

.LONG TERM.../Saturday through Thursday as of 10 pm Wednesday/
Long range period will start out stormy with a very large low over
the gulf and NE PAC Sat that moves N and weakens Sun. Model
agreement begins to break down after Sun, but they show potential
for more strong systems affecting the area during Mon-Thu with
long wave trof setting up between 150 and 160W. Ended up using
the 18z GFS to handle Sat, then went with mainly latest WPC from
Sun onward.

Increased winds somewhat with the Sat-Sun system. Raised the max
wind band ahead of the occluded front to 55 kt (with the GFS model
suggesting 60-65 kt but it was strongest model) for Sat into Sat
night. Raised POPS to categorical for most areas ahead of the
front for Sat into Sun. May still see some snow over mainly the N
half of the area as some colder air will be in place as initial
precip arrives Sat, but a warm up from the S should occur Sat
night into Sun, diminishing the snow threat over the central area.
Still looks fairly mild with above average temps continuing into
at least early next week, and active pattern will keep precip
threat on the higher side as well, although the main precip threat
may end up over the S half of the area during early to middle of
next week. Wind will be the main hazard that will need to be
monitored with these systems, with a threat for accumulating snow
Sat into Sat night over the N half.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind until 3 PM AKST this afternoon for AKZ023-026.
     Strong Wind until 6 PM AKST this evening for AKZ022.
MARINE...Gale Warning for PKZ022-033-035-042-043.
     Small Craft Advisory for PKZ021-031-032-034-036-041-051-052.
     Small Craft Advisory due to Seas for PKZ053.

&&

EAL/RWT

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