Small Craft Advisory 116, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
353 PM AKST Sun Feb 26 2017

.SHORT TERM...A weak short wave is moving southeast on the east
side of the ridge aloft past the central panhandle late Sunday
afternoon and Sunday night. This has developed primarily mid to
high level cloud deck and moved them southward into the central
panhandle by afternoon which will continue to track south and out
of the southern panhandle by Monday morning. A few areas of
flurries/sprinkles can be found on webcams. The scattered aspect
of it is causing difficulty with observations verifying. Latest
observations to carry them was in Sitka and Angoon. Should see the
flurries and sprinkles move south with the trough.

Yakutat has cleared out behind the short wave and will see
temperature plummet back into the lower 20s for tonight. May see
some patchy fog develop in the evening hours for the Yakutat area,
before it frost out by midnight. The clearing trend will move
south through much of the northern panhandle by Midnight. Do not
think there is much of patchy fog threat for the northern
panhandle and have not mentioned it but should not rule it out.

Monday will see the development of a surface low and frontal band
in the northeast Gulf of Alaska from the morning into the
afternoon. Expect to see some light snow or mixed rain and snow
form over the eastern gulf and across coastal areas of the
panhandle by late afternoon.

Northerly winds in Lynn Canal will be up to 20 kt on Monday for
some of the strongest winds across the inner waters. The coastal
waters will see Small Craft Advisory due to seas diminish into
early Monday for the 41-43 marine zones.

.LONG TERM...We are increasingly confident in accumulating snow
for much of the Panhandle beginning late Monday night into early
Tuesday. Beyond this time frame, a snowy pattern will continue,
but timing and geographic spread are in still in question given
differing solutions.

What we can agree on is that all models are consistent with our
air mass cooling courtesy of a northern gulf low developing late
Monday afternoon/evening. Temperatures on Tuesday, especially
given thicker cloud cover and snow will be noticeably cooler and
we have adjusted them downward, especially across the northern and
central Panhandle by as much as 5 degrees or so through much of
the week. This bolsters confidence for an all snow event north of
Port Alexander and Thorne Bay with a snow/rain mix south. Snow
is much less certain across the far northern Panhandle from
Yakutat to Haines/Skagway due to lack of precipitation. Rain may
still interrupt snow occasionally as projected waves thrust a
tongue of warm air through the southern Panhandle at times.

We expect snow accumulations of around 2 to 3 inches across the
southern two thirds of the Panhandle late Monday night. Heavier
bands will lift northward into Tuesday morning before weakening.
However, snow amounts for Juneau initially may be limited due to
offshore wind precipitation inhibition. These are solid advisory
totals south and west of Juneau. Should amounts be forecast to
increase or hold, a broad winter storm watch will be considered.
For now, a special weather statement covers the event and its
uncertainty through mid-week.

The ECMWF/Canadian solution is still the most consistent with
placement of the northeast gulf low just offshore of Fairweather
which would prove to be a snowier set up for the Icy Strait/Juneau
corridor. The GFS though arguably trending toward the ECMWF still
keeps vestiges of the NAM's position of low pressure in the
central Panhandle, which would keep the precipitation well to the
south.

Minor adjustments were made to the wind forecast through Tuesday
night for land areas, but were not adjusted for marine areas. The
extended forecast looks continued cold and potentially snowy at
times for Southeast.

&&

.AJK Watches/Warnings/Advisories...
PUBLIC...None.
MARINE...Small Craft Advisory due to Seas for PKZ041>043.
&&

Bezenek/JWA

Visit us at http://www.weather.gov/Juneau