Small Craft Advisory 808, NWS Juneau, AK

Southeast Alaska Forecast Discussion...Corrected
National Weather Service Juneau AK
352 PM AKST Fri Dec 23 2016

.SHORT TERM...High pressure has moved over the AK gulf as a low
pressure system previously in the southern gulf moves toward the
Washington coast. There is a weak wave riding over the ridge tonight
that will move in some cloud cover and isolated snow showers to
Yakutat, but little in the way of accumulation is expected. Pressure
gradient between a developing pool of cold arctic air over the Yukon
and the departing low to the south increased northerly and outflow
winds over the inner channels. Land based areas, with the exception
of the far norther panhandle, have been light. N Lynn Canal winds
neared gale force at times today, but think with the current
gradient the winds will remain at small craft levels and even
diminish slightly tonight and then finally subside late Saturday
afternoon. Mostly clear skies continue through Saturday with a few
low clouds remaining. Kept fog potential in for tonight but with
dropping temperatures may see more areas frost out.

Main event is a strong front tracking into the central gulf
tonight and then moving into the eastern gulf through Saturday.
This front will not impact the panhandle until the start of the
long range but it will increase winds over the gulf to max small
craft level and nearing gales to the far western edge.

Used some high res NAM to refresh grids but overall changes were
minor. Forecast confidence is average.

.LONG TERM...All eyes are now on what will happen Christmas Day
into Monday. An impressive storm system will march east into the
eastern gulf through the weekend. Gale to storm force winds will
spread eastward into the gulf with high seas. Winds will begin
rising across the Panhandle along the coast Christmas Day and
spread inland and northward through Sunday night. At this point,
strong wind gusts of 40 to 50 mph appear likely from Sitka
southeast to Ketchikan. Strong wind gusts are not out of the
question for Yakutat and Pelican as well...and potentially for
Skagway late Monday from the south.

Precipitation will begin as snow for all portions of the Panhandle
but given mixing with winds and a warmer conveyor belt moving
eastward from the gulf into Sunday night, confidence has increased
in a changeover to rain across the central Panhandle including as
far north as Juneau by Monday.

Models have distanced themselves from the idea and/or timing of a
wave feature along the southern end of the front around Dixon
Entrance, and therefore, they have increased QPF across the
northern Panhandle, as far north as the northern Inner Channels.
This expands our concern to Haines and Skagway as they will remain
all snow for the longest duration. Seven hundred mb flow is
conspicuously south and not southwest at this time, limiting any
snow shadowing from the Chilkat Range. However, even they are
susceptible to a rain change late Monday, although we left them
all snow at the moment. Should the idea of a wave reform along the
southern boundary, these heavier amounts will not pan out.
Southern areas still have the not unreasonable scenario of mixing
the cold air out so early that snowfall totals are negligible
Christmas Day and favor a changeover to rain as the first round of
leftovers are being served at dinnertime. Thus, we have elected to
re-issue the Special Weather Statement and directed readers to
check their local forecast for specifics as timing is complicated
and depends on geography. Snow totals with this system could amount
to 1-2 inches or less along the coast to 1 to 4 for the Southern
Inner Channels to 2 to 8 inches across the central Panhandle, and 3
to 12 inches for the far northern Panhandle.
Hyder could see more than a foot.

Given a trend in warmer marine air, we spread rain a little into
Tuesday. As another system potentially exits to the southeast by
the end of next week, rain and snow chances diminish into the end
of next week.

If confidence increases in the higher ranges of snowfall, watches
may be issued. Check your specific forecast regularly this holiday
weekend for changes and to gauge specific impacts to you.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory for PKZ012-043-051-052.
     Small Craft Advisory due to Seas for PKZ041-042.
&&

PRB/JWA

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