Small Craft Advisory 291, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
849 PM PST Sun Nov 26 2017

.SYNOPSIS...A trough will shift east through the region tonight and
Monday morning. A vigorous front will reach the area by daybreak on
Tuesday. Weak high pressure will build over the Pacific Northwest
midweek. Another frontal system will arrive late in the week.

&&

.SHORT TERM...A trough is somewhat disorganized and will move inland
over the Pacnw through Monday morning--showers will decrease. There
will be a break in the weather Monday afternoon and evening and then
the next front will reach the area by daybreak Tuesday. Tuesday
looks wet and blustery and then the upper trough will shift east
through the area Tuesday afternoon and evening with showers. Nothing
looks especially unusual and my guess is that the high wind watch
for the coast and north will end up being a typical wind advisory
type of event--the deep low center with this next system passes far
to the north of our area. Pressure gradients over Western Washington
are forecast to be pretty modest Tuesday morning, PDX-BLI peaks
around +7mb, so that is the same as the peak gradient around 3am
Sunday when it was blustery for awhile. More typical November
stuff.

.LONG TERM...There will be an increase in 500 mb heights by
Wednesday which will persist into Thursday. A weakening front and
surface low will drop into the area from the northwest during the
day Thursday and bring an end to the brief dry period. The pattern
remains progressive, with another late week dry period. There is
some model discrepancy regarding how things evolve by the coming
weekend. There is some agreement on a wet period again Saturday as a
mid level trough digs in the west coast and begins to cutoff well to
the south. After that, the ECMWF favors ridging building in from the
west while the 500 mb low cuts off across southern California. The
GFS has lower heights in our region and a continue more progressive
pattern at the day 7+ time period. Johnson

&&

.AVIATION...An upper level trough will maintain showers across the
area tonight as it moves inland. The air mass is moist and weakly
unstable. The flow aloft is westerly. Ceilings are mainly VFR
this evening but may see MVFR conditions overnight into Monday
morning with onshore flow. Weak ridging and offshore flow will
bring mostly dry weather on Monday. Winds along the coast and
North Interior will increase Monday night as the next strong
system arrives. 33

KSEA...Scattered showers in the region tonight. S winds at the
surface 10 to 15 kt. MVFR cigs possible with increasing onshore
flow. 33

&&

.MARINE...Strong onshore flow will continue tonight as a trough
moves inland. Gales are possible over the Coastal Waters, Strait
of Juan de Fuca and Northern Inland Waters. Winds will gradually
ease Monday morning. Another strong frontal system will arrive
Monday night and Tuesday. Gales are possible with this system too
and a Gale Watch is in effect for most waters. Seas at the
Coastal Waters will also build to 20 to 25 feet by Tuesday night.
High pressure will bring lighter winds on Wednesday. A weak front
will cross the area on Thursday. 33

&&

.HYDROLOGY...Minor flooding continues on the White River at the R
street bridge and the Skokomish river in Mason county. Otherwise,
no river flooding conditions are expected.

Following the recent heavy rains, the risk of landslides remains
elevated.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Wind Watch from Monday evening through Tuesday morning for
     Admiralty Inlet Area-Central Coast-Everett and Vicinity-
     North Coast-San Juan County-Western Skagit County-Western
     Whatcom County.

PZ...Small Craft Advisory for rough bar until 4 PM PST Monday for
     Grays Harbor Bar.

     Gale Watch from Monday evening through Tuesday morning for
     Admiralty Inlet-Central U.S. Waters Strait Of Juan De Fuca-
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From Cape Flattery To James Island Out 10
     Nm-Coastal Waters From James Island To Point Grenville 10
     To 60 Nm-Coastal Waters From James Island To Point
     Grenville Out 10 Nm-Coastal Waters From Point Grenville To
     Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm-East Entrance U.S.
     Waters Strait Of Juan De Fuca-Northern Inland Waters
     Including The San Juan Islands-West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory from 3 AM to 6 PM PST Monday for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From Cape Flattery To James Island Out 10 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From James Island To Point Grenville
     Out 10 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville
     To Cape Shoalwater Out 10 Nm-West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Gale Warning until 3 AM PST Monday for Coastal Waters From Cape
     Flattery To James Island 10 To 60 Nm-Coastal Waters From
     Cape Flattery To James Island Out 10 Nm-Coastal Waters From
     James Island To Point Grenville 10 To 60 Nm-Coastal Waters
     From James Island To Point Grenville Out 10 Nm-Coastal
     Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater Out
     10 Nm.

     Gale Warning until 6 AM PST Monday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of
     Juan De Fuca-Northern Inland Waters Including The San Juan
     Islands.

     Gale Warning until midnight PST tonight for West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 6 AM PST Monday for Puget Sound and
     Hood Canal.

&&

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html