Small Craft Advisory 518, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
254 PM AKDT Tue Nov 2 2021

.SHORT TERM.../ Thru Thursday night / Satellite is showing a low
tracking northwest to the northern Gulf of Alaska through Tuesday
night, and the frontal band and a trough are spreading into
Southeast Alaska during this time. The front is connected to a
second weakening low that will track to the southern panhandle by
Wednesday morning. A building ridge over the eastern gulf on
Wednesday works to move all of the rain out of the panhandle as
the builds to a north south line just east of 140 west. This
holds the weather to the west away, and allows a brief respite for
the panhandle Wed night into early Thursday.

A lower 990 Mb low southwest of Vancouver island Wednesday
afternoon will turn north moving along the British Columbia
coastline. By Thursday afternoon the low will have developed to
the lower 980s and start rain moving back into the southern
panhandle Thursday afternoon and then north though the night.

Small craft to gale force winds for the outer waters through
tonight and then diminishing Wednesday as the surface ridge build
over the gulf waters. Should see a tightening of the gradient as
low along the British Columbia coast moves northward. Northerly
Lynn Canal winds increasing to 25 to 30 kt early Thursday and
think those will probably continue through the day.

.LONG TERM.../Thursday through Tuesday as of 10 PM Monday/...The
long term portion of the forecast begins with a drying Thursday
before an active Friday and potentially active weekend.

Thursday looks to begin with a 500 mb ridge over the panhandle.
This ridge would move eastward and a trough would move in behind
it. Overall, this trough at the 500 mb layer is expected to stay
in place over the gulf through the rest of the long term.

At the surface, an area of low pressure will move northward. This
will track precip into the panhandle from the south to the north.
Areas north of Frederick Sound will probably have a dry Thursday
but areas south of Frederick Sound would see the rain move in by
the early afternoon at the latest. Thursday night is when the
precip will arrive for areas north of Frederick Sound.

Friday is when this low pressure will pass through the gulf.
Overall, Friday is looking like a rainy day with elevated winds.
Winds along the coast could get up to 40 kts as the low passes by.

The rest of the forecast is when the uncertainty ramps up. Pick
your favorite deterministic model or ensemble averages and the
overall story is: continued low pressure in the gulf with
possible rounds of rain. For now, kept the highest chance for
precip in the south because if this pattern of lows coming up from
the south continues, that would put outflow in the northern half
which would keep the weather conditions dry. The European ensemble
and GEFS Probably of 24 hour QPF >0.01 inches product supports
this idea.

There isn’t much for snow potential in the long term forecast.
850 mb temperatures really don’t get far below 0C until
Saturday. For now, kept mentions of snow and rain in areas along
the highways near Haines and Skagway.

Highs and lows will slowly cool down during the long term.
Overall, assuming thick cloud cover doesn’t ruin this cooling
trend forecast, at or below normal temps are possible beginning
this weekend and would last into early next week.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Strong Wind until 10 PM AKDT this evening for AKZ023.
MARINE...Gale Warning for PKZ041>043-051-052-310.
     Small Craft Advisory for PKZ012-013-022-033>036-053.

&&

Bezenek/GJS

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