Area Forecast Discussion
Issued by NWS
FXAK67 PAJK 251334
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
534 AM AKDT Tue Oct 25 2016
.SHORT TERM...Dry but locally windy conditions today with winds
diminishing this evening and overnight.
Satellite imagery showing a broad surface low moving south of
Haida Gwaii up from the N Pacific with inverted trough and cloud
bands extending over the panhandle. A broad area of high pressure
remains over the Yukon. An upper level low that moved down from
the Yukon in to the eastern gulf can be seen clearly on water
Tight pressure gradient between the Yukon high and panhandle
inverted trough producing strong northerly and outflow winds.
Near storm force winds reported in Lynn canal with solid small
craft to near gale force winds for the central inner channels.
Taku winds event for downtown Juneau had a bit of a later start
than originally expected. Getting solid cross barrier flow, with
camp 18 winds of 75 kt, critical level indicated by the upper
level low on WV Satellite, but inversion seems to be just ramping
up and could be the cause of the delay. Did get a verification
report of winds beginning to roar near the base of the Juneau
Through the day and into the evening, the pattern will shift with
the Yukon high moving to the east, the Haida Gwaii low starting to
track west and weaken, and the upper level low over the gulf
exiting to the south. This will cause decreasing gradient and
Temperatures this morning were highly variable due to cold air
aloft and down slope winds v wind sheltered areas. PAGY was at
43F, while PAOH reported 29F. South Douglas reported a temp in the
upper 40s with freezing temps at the NWS office in the Valley.
Tonight`s temps should have less of this range due to deceasing
winds. Otherwise while there will be variable cloudiness today due
to the bands moving around the low with a slight chance of showers
over the far southern panhandle from the Haida Gwaii low. The
rest of the panhandle will remain dry.
Little change to inherited forecast, kept with HiRes NAM models
and only slight adjustments. Forecast confidence is above average.
.LONG TERM...The low west of Haida Gwaii at the start of the
extended range forecast period will continue drifting slowly to
the west while weakening. Any shower activity from this feature
will end by Thursday morning, but dry weather may not last long. A
strong low with a well defined frontal signature will be entering
the western Gulf Wednesday morning. The front from this low will
interact with another low tracking north along 130w past Vancouver
Island on Thursday morning. Models are not handling the
complicated interaction amongst these three lows very well at all
but are indicating at least three separate frontal bands which
cover the area from the eastern gulf to western Canada. Resulting
PoP grids reflect uncertainty regarding where, or even if,
precipitation occurs during the latter part of the week and going
into next weekend.
Indications are that high pressure will linger over the Yukon long
enough to interact with the low entering the western gulf on
Wednesday, producing another strong northerly gradient. Am
expecting more northerly gales over Lynn Canal with strong wind
gusts in both Skagway and Haines on Thursday.
Used the Canadian NH for updates to pressure and wind Thursday and
Thursday night. Blended NAM12 into existing Pop grids. Few other
changes. Overall forecast confidence is average.
.AVIATION...Low level wind shear due to outflow winds impacting
PAYA and PAJN today. The strong mountain top winds along the
Salisbury ridge are verifying. Winds will diminish through the
afternoon as Canadian high pressure shifts east. Otherwise no
other significant ceilings or visibility restrictions.
PUBLIC...High Wind Warning until 4 PM AKDT this afternoon for AKZ025.
STRONG WIND until 1 PM AKDT this afternoon for AKZ018.
MARINE...Gale Warning for PKZ012-013.
Small Craft Advisory for PKZ011-022-031>034-036-041>043-051.
Small Craft Advisory due to Seas for PKZ052.
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