Small Craft Advisory 620, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
319 PM AKST Tue Dec 5 2017

.SHORT TERM...An atmospheric river over the central gulf will be
the main weather feature for the next several days. Waves moving
north along the front will periodically cause it to shift
east/west over the next couple days. But the bulk of the moisture
with the front will be pointed at the northern gulf coast with
Yakutat expected to have heavy rain and gusty winds each day. The
southern half of the panhandle will see rain shifting to the NW
with breaks in the clouds through tomorrow and even fewer clouds
on Thursday. Anywhere with relatively light winds and breaks in
the clouds will see some patchy fog develop tonight through
Wednesday morning.

The strong southerly flow will continue the warm air advection.
Highs in the mid 40s will persist. Some places with fewer clouds
will likely fall into the mid-upper 30s for overnight lows, but
places that stay windy/cloudy like Yakutat will not drop out of
the 40s. The front will cause gale force winds for the outside
waters of 35 to 45kt and similar gusts for the nearby land areas
periodically as the front wavers east/west.

Used an ensemble approach for updates today as models were in good
agreement on the atmospheric river. Forecast confidence is above
average.

.LONG TERM /Thursday through Tuesday as of 930 PM Monday/..The
overall pattern for the extended period has not changed
substantially. There is ample Pacific moisture present to receive
1.5-2" over a 12 hour period in the northern and central panhandle
with accompanying gusty winds. Light snow accumulation will mainly
be confined to the higher elevations and along White Pass during
this time.

Temperatures remain quite warm Thursday into Friday, with most
areas across the southeastern Alaskan panhandle reaching the mid
40s. Temperatures even at the 850 mb level show values that are
representative of "summertime" temperatures. Max temperatures
remained within model guidance for Thursday and Friday, but
temperatures for Saturday into Sunday were increased ever so
slightly. These temps were within guidance, but we continue with the
warm trend. Minimum temperatures were increased for Thursday night
due to overcast skies and decreased for the Friday/Saturday period.

Changes to pressure relied mostly on WPC guidance, as again the
main low has progressed further east. The pressure drops by 12z
on Sunday, but after this time there is hardly any model support
later on in the period and expect there to be large associated
errors. The high hanging over the east of the panhandle
retrogrades slightly late Saturday.

Some main areas of concern for this timeframe were extensive
edits made to winds along the outer coast and POP fields. None of
the POP models completely captured Sunday-Monday's precip
pattern, but the SREF was relied on highly for POP blends and
temperature guidance during the beginning of the extended
timeframe.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...Strong Wind from Wednesday morning through Wednesday
afternoon for AKZ023. Winter Storm Warning until 9 PM AKST this
evening for AKZ018. Strong Wind through Wednesday afternoon for
AKZ017.
MARINE...Gale Warning for PKZ022-041>043-051>053. Small Craft
Advisory for PKZ011-012-021-031>036.

&&

NAF/SS

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Special Weather Statement
National Weather Service Juneau AK
247 PM AKST Tue Dec 5 2017

AKZ017-061600-
Cape Fairweather to Cape Suckling Coastal Area-
Including the city of Yakutat
247 PM AKST Tue Dec 5 2017

...CONSIDERABLE RAINFALL FOR THE NORTHEAST GULF COAST THIS WEEK...

A weather front along the northeast gulf coast is moving a large
stream of moisture over the region which will last through
Thursday. This will cause periods of heavy rainfall with total
accumulations through Thursday between 5 and 6 inches near
Yakutat. Rainfall amounts of 2 inches have already fallen through
Tuesday afternoon. Visibilities will be reduced during periods of
heavy rain. Rivers will rise during this timeframe; however, with
current river levels relatively low, considerable impacts are not
expected.