High Wind Watch 1, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
254 PM AKST Fri Jan 26 2018

.SHORT TERM.../ Friday night to Sunday night / Trough of low
pressure over the eastern Gulf of Alaska weakening or being
absorbed by developing low in the western portion of the gulf
through early Saturday. High pressure over northern Alaska and
northwest Canada will strengthen into early Sunday. This will
increase outflow winds in the northern panhandle, Saturday and
Sunday. Am expecting strong gusty winds to approaching maximum
gale force through Lynn Canal and enhance the seas for the
southern Lynn Canal above the normal 1 foot for 5 kt of wind for
more fully developed sea state. These seas will continue through
the weekend.

The Taku mountain wave winds developing late Saturday night will
increase to 60 mph for downtown Juneau and Douglas. Expect the
strongest conditions Sunday morning into early afternoon, and
then diminishing through the evening.

Weather system developing and moving northeast to the southern
gulf with the occluded front spreading rain and snow into the area
beginning around midday and then north through Sunday night. Will
need to watch the snow accumulations on this event as their may
be the potential of 3 to 6 inches of snow falling late Sunday over
the central inner channels.

.LONG TERM.../ As of 9 pm Thursday night / Amplified high
latitude blocking regime will continue to influence the weather
over the Gulf of Alaska through the early part of the week.
Mid/upper ridging over the Bering Sea will trend towards becoming
more cut off by Monday. Over the Gulf, a deep, cold upper trough
will continue, with a significant piece of shortwave energy
ejecting NE'ward into the SE Gulf by Sunday evening.

At the surface, a cold 1048 mb high over NW Canada will remain in
place and slowly weaken through Monday. A sub 980 mb low over the
NPAC Sunday will send a strong front northward and across the
Panhandle Sunday and Sunday night. Needless to say, the northerly
pressure gradient will be quite strong between these two systems.
Expect rapidly increasing northerly outflow conditions to develop
ahead of the front on Sunday. Bumped winds up to max gales over
the northern channels, however with the cold air to the north and
some impressive low level gradients, would not be surprised to see
storm force conditions in Lynn Canal, Cross Sound and possibly
parts of Stephens Passage on Sunday. Temperatures will remain
quite cold over the north, so periods of significant vessel icing
will also be a problem. Over land areas, places that are exposed
to NE winds will likely be very windy as well. Forecast soundings
show a pronounced weakness in the flow aloft with some reversal
around 500 mb invof Salisbury Ridge Sunday morning. Cross barrier
flow ahead of the advancing front will be nothing short of
impressive. While the critical level will likely be transient with
the mid level wave rapidly approaching from the south on Sunday
afternoon, there will be a period of time where the stage will be
set for a classic Taku Wind event for downtown Juneau and Douglas.
Will likely eventually need high wind headlines for this area as
well as for Skagway.

As the front approaches on Sunday, models are in good agreement on
developing strong WAA aloft over the colder arctic air being
pulled southward. Thickness will support snow as the precip type
even over the south initially, but a 50+kt low level jet and
associated warming aloft will likely allow rain to mix in by
Sunday evening. Areas N of Frederick Sound will be a different
story. This should be a fairly quick moving front but a period of
moderate to heavy snowfall is possible over the central Panhandle
possibly extending northward into the Icy Strait communities by
late Sunday night. Still disagreement among model solutions as to
the northward extent and amount of qpf so will be something for
later shifts to monitor.

Model disagreement increases dramatically after Monday in regards
to interaction between arctic energy dropping down the east side
of the upper high over the interior and an intensifying Pacific
jet. Overall, temps should remain on the cool side of normal with
continued N'ly outflow and periodic precip threats through Friday.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Watch from late Saturday night through Sunday evening
     for AKZ025.
     Strong Wind until 9 PM AKST this evening for AKZ018.
MARINE...Gale Warning for PKZ052.
     Small Craft Advisory for PKZ012-013-021-022-031-032-034>036-043-
     051.
     Small Craft Advisory due to Seas for PKZ041-042.

&&

Bezenek/DEL

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