544
FXUS66 KSEW 092311
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
311 PM PST Sat Nov 9 2024

.SYNOPSIS...Active weather will continue into next week, with
more lowland rain, mountain snow, potential river flooding, chances
of thunder, high surf and breezy conditions. Cooler weather
expected toward next weekend with a trough.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Light rain continues to
spread across western WA this afternoon as a slow-moving cold
front crosses the region. Precip will taper down this evening with
just isolated coverage left in the Cascades after midnight. Expect
lows in the mid to upper 40s overnight.

A pair of stronger Pacific storm systems will impact the region
over the week ahead, the first one arriving Sunday night and
Monday. This system will bring another round of moderate to heavy
precipitation, especially along the coast and in the mountains.
Heavy rainfall in the Olympics will bring the Skokomish River in
Mason County into flood stage - a Flood Watch Remains in effect.
In the Cascades, snow levels will hover around 4000-5000` with
snowfall impacting SR 20 and Washington Pass (which still remains
open to this point). Mount Baker may also see a foot of snow. This
period of weather will also be breezy to locally windy conditions with
strongest winds (gusts to 25-35 MPH) along the coast and north
interior. Meanwhile, this system will churn up strong waves with
swells of 14-22 ft heading toward the coast (possible High Surf
conditions). And lastly, the air mass will be cool and unstable
with a slight chance of thunderstorms along the coast too.

A weak ridge brings a very, very short break in the action on
Tuesday. We`re not completely dry but we will see river levels
crest and (briefly) lower from Monday`s rain. Seas will also
subside during the day. 33

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...The next round of active
weather is slated for Tuesday night, Wednesday and into Thursday
as the second, and wetter, Pacific frontal system moves in. The
main focus is again on moderate to heavy precipitation over the
coast, Olympics and Cascades with concerns for river flooding.
Several rivers are forecast to reach Action Stage and a few will
be close to Minor flood stage. Snow may be heavy at times in the
central and northern Cascades (above 4000`). Coastal flooding may
also be a concern with higher astronomical tides and seas still
running high (10-15 ft). And thunderstorms remain a threat along
the coast where the air mass remains unstable.

A deep upper level trough will settle over the region Friday
through the weekend with cooler conditions on tap. Highs Friday
and Saturday are only in the 40s with lows in the 30s. Snow levels
are down to 2000-3000` with a few inches of snow in the mountains
and passes. 33

&&

.AVIATION...Southwest flow aloft through much of the period aside
from a brief spell of west-northwesterlies into Sunday morning. A
weak front is progressing gently across the region currently.
With it, MVFR/IFR (even isolated LIFR) conditions are spreading
across area terminals as rain falls. Rain is forecast to decrease
into tonight but, low ceilings are to remain and likely trend into
Sunday morning. MVFR/IFR to even localized LIFR conditions are to
continue. Some improvement to VFR is in the forecast towards
Sunday afternoon but not likely to be widespread. KSEA...

Low-end VFR conditions currently. However, ceilings will
trend lower tonight into Sunday morning with MVFR conditions likely
being met. Can`t rule out IFR ceilings also. Winds remains
predominantly out of the south through the period, mostly between
between 2 to 6 kt.

&&

.MARINE...A front continues to gently progress across area waters
tonight. SCA should be allowed to expire this evening for high seas
over the coast however, gale watches will remain for another period.
The decrease in seas will be brief as the next front arrives Sunday
night into Monday. Seas will trend higher, possibly topping into the
14-22 ft range early next week. Expect SCA winds across most waters,
and the likelihood of gale gusts over the coastal waters and near
the eastern Strait of Juan de Fuca. A stronger front around Tuesday
will bring a better chance of more widespread gales as the pattern
looks to remain active well into next week.

McMillian

&&

.HYDROLOGY...A more significant chance of precipitation is
expected Sunday through Monday, and again on Wednesday as an
active weather pattern returns with weak to potentially moderately
strong atmospheric river events coming through the area. The
precipitation amounts will be strongly orographically influenced
with precipitation totals in the mountains expected to be 3 to 5
inches for both storms except locally over 6 inches on the
Olympics for the last one (Wednesday).

The succession of storms will increasingly build up soil moisture
and river levels throughout this period which will increase the
possibility for river flooding. Snow levels vary generally from
4000 to 6000 feet which will impact precipitation type and affect
the amount of storm runoff.

At this time, the Skokomish River is the only river forecasted to
rise into flood stage, and potentially into moderate flood stage
during the middle of next week. For other rivers, significant
rises are expected with several river forecast points above Action
Stage, and flooding could be possible. Flooding extent will
depend on rainfall rates, temperatures, as well as snow levels
with precipitation that falls with each of these weather systems
next week. We will continue to assess the hydrologic conditions
and forecasts for any additional areas of potential flooding.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch from Sunday evening through late Monday night for
     Hood Canal Area-Lower Chehalis Valley Area-Olympics.

     Winter Weather Advisory from 6 PM Sunday to 1 PM PST Tuesday for
     West Slopes North Cascades and Passes.

PZ...Small Craft Advisory until 7 PM PST this evening 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 Watch from Sunday afternoon through late Sunday night for
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Watch from Sunday afternoon through Sunday evening 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.

&&

$$