Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 101514
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
614 AM AKST Sat Dec 10 2016
.SHORT TERM...Strong outflow winds and below normal cold
temperatures continue to dominate the forecast over the next 24+
hours. Temperatures this morning are about 5 degrees colder than
they were at this time yesterday for majority of the panhandle,
so expecting highs to be a bit cooler than we saw yesterday as
well. The combination of winds and temperatures continue the
freezing spray through the inner channels and the Wind Chill
Advisory near White Pass.
Mountain wave winds did not extend all the way to the surface in
downtown Juneau, so have cancelled the High Wind Warning. An
upper level short wave moving across the region N to S early this
morning was the last best chance for the winds to develop. After
that passes the critical level ingredient is absent. Frequent
gusts of 40-50mph were observed yesterday and last night and
these remain likely through tonight.
One big difference in the forecast are the ocean effect
clouds that formed yesterday evening over Dixon Entrance and
spread over the far southern zones up to Ketchikan and Klawock.
Other bands of ocean effect clouds are off the coast of S.
Baranof Island extending from Frederick Sound, off the coast of Mt.
Fairweather, and S. Lynn Canal to Hoonah. These clouds are formed
in a convective process when cold air is advected across a long
fetch of relatively warmer water (>13C between the SST and
850mb temp). If the clouds can pull in enough moisture snow
showers can form. This is most likely to occur over the offshore
area, since the airmass over the inner channels is much drier. Without
any fluctuation in wind direction, the clouds will likely persist,
but have the greatest extent over water.
Updated the pressure and winds with an emphasis on the NAM and its
high res models. Forecast confidence is above average, but
slightly lower on whether or not the clouds will expand.
.LONG TERM...After the 500 HPa shortwave digs all the way south
of our area on Sunday, northerly flow aloft will persist over the
Panhandle through Tue. Models are in good agreement that another
upper ridge will build along 155W or so early Wed for a persistent
block giving north to northwest flow aloft. No reason at all to
change our dry, frigid, offshore flow forecasts for a week. Added
some local wind between Cape Suckling and Cape Fairweather,
otherwise almost no change in the day shift`s forecasts out
through Sunday the 18th.
PUBLIC...Strong Wind through late tonight for AKZ019-025.
Wind Chill Advisory until 11 AM AKST Monday for AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ011>013-031.
Gale Warning for PKZ011>013-022-043-051.
Small Craft Advisory for PKZ021-031>035-041-042-052-053.
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