Small Craft Advisory 266, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
922 PM PDT Thu Nov 3 2016

.SYNOPSIS...An upper ridge will bring sunshine to Western Washington
Friday. The next front will arrive Saturday for a return to rainy
weather, followed by showers Sunday. Moist southwest flow will bring
more rainy weather to Western Washington at times next week.

&&

.SHORT TERM...Today turned out mostly sunny, with highs in the 60s.
Tomorrow will be similar, with patchy fog in the morning and highs
in the low 60s. The baroclinic band offshore that is visible in
satellite imagery will move slowly across the forecast area Friday
night through Saturday night. This system will bring 1 to 3 inches
of rain to the coast and Olympics, 1 to 2 inches to the Cascades,
and 0.25 to 0.75 inch to the interior lowlands. The snow level will
be 7000 to 8000 ft as the system moves through.

A fast moving upper trough follows Sunday. Skies will be cloudy and
most areas will have showers in the morning, tapering in the
afternoon. Temperatures will fall a few degrees each day but remain
above average for this time of year.

.LONG TERM...Models are not in particularly good agreement about when
the next rainy period will arrive. They all have a conveyor belt of
moisture offshore, heading into Vancouver Island, for the first part
of the week. However it's not exactly clear when this conveyor belt
will shift east enough to bring rain to Western Washington. Ideas
common to all the models include: some parts of the area, coast and
north most likely, will get some rain on Monday; a cold front will
sweep through the area Tuesday night; showers will follow Wednesday
with perhaps some drying after that. Have tried to include this
sequence in the grids and forecasts but confidence is not high. Burke

&&

.HYDROLOGY...Dry conditions through Friday will allow rivers across
the forecast area to fall, but more rain over the weekend and next
week will again bring rises. At this time flooding is not expected.

Record rainfall in the month of October has left area soils very wet
and susceptible to shallow landslides in favored locations. The USGS-
based accumulative precipitation and soil wetness indices are
currently above thresholds for landslides and have been for quite a
few days now. Isolated landslides have occurred and may continue to
occur...with or without significant rainfall. If we do get
significant rainfall under these conditions...there will be
increased chances of triggering multiple landslides.

&&

.AVIATION...Upper level trough offshore with upper level ridge
to the east giving southwesterly flow aloft over Western Washington.
Light offshore flow at the lower levels. areas of ceilings below 200
feet and visibilities below 1/2sm in fog developing over the
Southwest Interior after 08z, dissipating by 18z. Increasing
mid/high level moisture Friday afternoon.

KSEA...A few high clouds overnight with increasing mid/high level
moisture Friday afternoon. Patchy fog over the sound and in the
valleys to the east of the terminal 12z-16z. At this point fog does
not look to be deep enough to make its way into the airport.
Light northeast wind becoming southeast Friday morning. Felton

&&

.MARINE...Surface high pressure over the waters tonight will
weaken on Friday as a cold front approaches the area. The cold front
will move across the coastal waters late Friday night and the
interior waters Saturday morning. Gales are possible over the
coastal waters ahead of and with the front. A weak surface trough
will follow the cold front. Another frontal system will impact the
area Sunday night and Monday. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisories are in effect for the coastal waters
	 and west entrance to the Strait of Juan de Fuca.

     Gale Watch in effect from Friday evening through Saturday
	 morning for the coastal waters.

 	 Small Craft Advisory for rough bar in effect until 6 PM
	 Friday for the Grays Harbor Bar.

&&

www.weather.gov/seattle

An illustrated version of this forecast discussion can be seen at
www.weather.gov/seattle/gafd/latest_webafd.html