Small Craft Advisory 268, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
833 PM PDT Sat Nov 5 2016

.SYNOPSIS...A cold front will push inland tonight with rain
tapering. A warm front will brush the area Sunday night. A cold
front will hang up offshore Monday and Tuesday, then push onshore
Wednesday for some rain again. Another front will reach the area
around Friday.

&&

.SHORT TERM...A front will slowly push inland tonight with rain
ending from west to east. A trailing upper trough could bring
a few showers later tonight and Sunday, mainly to the coast. A
warm front will brush the area Sunday with a little rain coast
and lesser chances further inland. Monday is looking largely dry
as an upper trough digs over the northeast Pacific and holds a
cold front offshore. Tuesday looks like another mainly dry day.
The cold front will inch closer but the rain threat should hold
off until Tuesday night. Highs will be quite mild for November,
especially Monday and Tuesday when lower to mid 60s will be
common. Some record highs could be set each day. Schneider

.LONG TERM...Previous discussion...A front will stray into
western Washington on Tuesday night accompanied by rain for most
places by Wednesday morning. As the front tries to push into the
persistent ridge over the Rockies, the front will dissipate on
Wednesday, and the associated rain will dry up. Upper heights will
re-build quickly on Wed night, and Thursday looks like another dry
(except perhaps at the coast) and mild day. Should be unseasonably
warm Thursday, with a warm air mass aloft and enough wind to mix
that warm air into the boundary layer.

The persistent longwave pattern will start to flatten a bit on
Friday, opening the door to a low center to pass just off the
coast and a trailing cold front to drag across western Washington.
This would be accompanied by rain and locally windy weather
Friday and next Saturday. Haner

&&

.AVIATION...Frontal progress has been slow this evening...but
steady...as the western half of the Olympic peninsula has punched
through the back end of it. At the time of this writing...looks as
though the front is located right along Puget Sound...meaning
terminals east of the Sound likely looking at a wet overnight
period. A weak flat upper level shortwave ridge will move over W WA
on Sunday for some drying aloft. However the low levels will
probably see very little clearing until after 21Z.

The air mass will remain moist tonight through Sunday morning. Light
rain will slowly diminish overnight, with more spotty light rain or
drizzle Sunday morning. Cigs a mix of MVFR and VFR conditions with
VFR cigs below 5000 feet. Spotty IFR cigs are also expected.

KSEA...Light rain will continue tonight although it will be
intermittent at times. Borderline VFR to MVFR cigs will persist
tonight through Sunday morning...with greatest tendency for MVFR
conditions expected during rain. IFR cigs early Sunday morning are
not out of the question. Surface winds will remain southerly 5-10
KT. Kam/SMR

&&

.MARINE...The weakening cold front will continue its very slow
eastward trek over W WA tonight and dissipate. A surface trough will
move across the coastal waters tonight generating spotty SCA level
winds, before it reaches the coast and dissipates late tonight. A
large westerly swell train has reached the coast and will continue
tonight before subsiding slowly on Sunday. The swell is just below
high surf advisory levels but seas will be between 15-19 FT over the
coastal waters. A SCA has been issued to cover both the spotty SCA
winds tonight, the high seas, and the ramp up SCA winds Sunday
mentioned in the next paragraph.

The next strong frontal system was offshore near 40N/147W at 21Z/2
PM. Models remain consistent in curving the system NE toward
Vancouver island tonight and Sunday. The warm front will move across
mainly NW WA Sunday night. The coastal waters should see increasing
S winds in the SCA range Sunday afternoon, before winds increase to
gale levels Sunday night. A borderline SE gale is also possible for
the north interior waters later Sunday night. However, confidence is
shaky so for now the forecast is for 20-30 KT.  A gale watch is in
effect for the coast.

Earlier models had shown a second warm frontal wave moving up the
cold front Monday night but have since weakened that feature.
Regardless, strong pressure gradients between the coast and the
offshore cold front will maintain coastal gales through Monday night
and possibly much of Tuesday. The cold front will finally move to
the coast Tuesday evening. Another cold front will approach the
region on Thursday. Kam/SMR

&&

.HYDROLOGY...The Skokomish river in Mason county is currently
about a half foot below flood stage and creeping up. Steady rain
over the basin ended recently. The river will likely creep up
another few tenths of a foot this evening and crest just below
flood stage later tonight. That said, it will be close and a flood
warning may still be needed tonight.

A frontal system Friday and Saturday could bring flooding concerns
to the uniquely flood-prone Skokomish river again. Otherwise,
river flooding is not expected in the next 7 days. Schneider

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Sunday afternoon through late Monday night 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.

     Small Craft Advisory until 4 PM PST Sunday 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.

     Small Craft Advisory for rough bar until 5 PM PST Sunday for
     Grays Harbor Bar.

     Small Craft Advisory for hazardous seas until 4 PM PST Sunday
     for West Entrance U.S. Waters Strait Of Juan De Fuca.

&&

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html