Small Craft Advisory 233, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
915 PM PDT Mon Oct 29 2018

.SYNOPSIS...A weak disturbance moving across the area will bring a
chance of showers to the area tonight. Rain chances will diminish on
Tuesday with only a slight chance of light showers. A warm front
Tuesday night and Wednesday will bring rain and breezy conditions. A
series of vigorous weather systems will bring rainy and windy
conditions at times to the area Thursday through next weekend.

&&

.SHORT TERM...Showers have diminished considerably over the area
this evening, though there are still a few in and near the
mountains. Tuesday will probably have a few light showers over the
mountains and isolated showers over the lowlands as the area is
between systems.

A warm front will bring rain to the coast late Tuesday afternoon,
then spread inland overnight. There is likely to be heavy rain at
times in most places except perhaps the immediate vicinity of Puget
Sound, which will be shadowed somewhat. Snow levels will rise from
around 4000 to 4500 ft Tuesday evening to 6000-8000 ft on Wednesday.
A few inches of snow could fall on the higher passes, at Paradise on
Mt Rainier and at Mt Baker before snow levels rise late Tuesday
night or Wednesday morning. Rain and breezy to locally windy
conditions will continue in the warm sector on Wednesday as a weak
low passes over or just to the north of the area during the day.
Temperatures that are near to a couple of degrees below normal on
Tuesday will rise to 3-6 degrees above normal Wednesday.

Post frontal precipitation Wednesday evening will come to an end
just as warm advection precipitation from the next system upstream
system moves into the area overnight. The GFS now joins the ECMWF in
having little to no break between systems. Precipitation amounts
between the two systems Tuesday night through Thursday will range
from 1 to 2 inches in the lowlands to possibly up to 4 inches in the
mountains. Burke/Albrecht

.LONG TERM...Previous discussion...Models are increasingly showing
the period Friday through Sunday as wet and windy at times. A strong
jet across the Pacific promises to transport a good deal of moisture
and energy from the western North Pacific into the Pacific NW. A
frontal boundary around the area will wave back and forth as systems
move across the region. Advisory level winds are possible at times.
3-day rainfall amounts ranging from 1 to 4 inches in the lowlands
and 4-8 inches in the mountains are possible. Systems will be moving
quickly and difficult to time. At this time, a blend of the models
was used as a first guess to the forecast. Albrecht

&&

.AVIATION...An upper level ridge offshore bring strong to moderate
northwest flow aloft tonight and Tuesday. Light surface flow tonight
will become moderate southeasterly on the coast Tuesday as a front
approaches. VFR ceilings this evening should fall to MVFR late
tonight or early Tuesday. There will likely be LIFR CIGs over the
Kitsap Peninsula and the southwest interior. Improvement to VFR is
likely Tuesday afternoon.

KSEA...Discussion above applies. VFR conditions will probably fall
to 1k IFR ceilings for several hours late tonight and Tuesday
morning, with VFR conditions returning Tuesday afternoon. Winds will
generally be southerly 10 kt or less. CHB

&&
.MARINE...Westerly swells of 9 to 13 feet will slowly subside
overnight but seas will remain hazardous over the coastal waters
from Cape Flattery to Cape Shoalwater from 30 NM out to 60 NM into
Tuesday morning.

Southerly winds will increase Tuesday and by Tuesday night gales are
possible over the coast and the east entrance. A gale watch is now
in effect for Tuesday night. An active pattern will continue over
the Pacific Northwest later this week. Strong frontal systems will
bring the potential for gale force winds across parts of the area at
times. CHB

&&

.HYDROLOGY...With repeated periods of rainfall lately, rivers are
slowly rising and soil moisture is increasing, but no flooding is
expected for the next 4 days. Storms this week will have the river
stages stairstepping higher with each one. Given the precipitation
amounts possible this weekend (see Long Term section), on top of
what will fall during the week, strong river rises are likely with
some flooding not out of the question. JBB/JD

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Watch from Tuesday afternoon through late Tuesday 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-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory for hazardous seas until 11 AM PDT Tuesday
     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 11 AM PDT Tuesday for
     Grays Harbor Bar.

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