389
FXUS66 KSEW 081115
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
315 AM PST Fri Nov 8 2024

.SYNOPSIS...Quiet weather this afternoon before unsettled weather
returns as a series of systems impacts the area starting tonight
and into the weekend. Active weather will continue into next week,
with lowland rain, mountain snow, chances of thunder, and breezy
conditions.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...Recent satellite imagery
shows high clouds over western Washington early this morning.
Upper level ridging will gradually move eastward away from the
region throughout the afternoon as upper level clouds continue to
stream in ahead of an approaching frontal system offshore. One of
the last overall drier days we will have in a while as high
temperatures remain in the upper 50s and lower 60s this
afternoon.

The aforementioned frontal system will weaken and stall over the
coast later this evening, slowly spreading precip over the area
tonight and into Saturday. This system will be fairly weak in the
series of systems that will cross W WA over in the next week.
Precip totals are mostly around 0.30-0.75" with this frontal
system. Snow levels will remain high, generally in the 5000-6000
feet, mainly limiting snow to the higher elevations.

A, stronger deep upper level low will transverse through the area
from British Columbia late Sunday into Monday, bringing increased
moisture to the lowlands and the mountains, along with lower snow
levels, and breezy conditions.

.LONG TERM /MONDAY THROUGH THURSDAY/...The aforementioned strong
deep upper low will push through W WA into Monday, where impulses
of rain will persist. The bulk of the rain will be focused mainly
in the Olympics, Cascades, and along the coast. Latest
probabilistic guidance shows around 50 to 60% chance of 2 inches
or more in those locations. Slight instability with this system
also brings a chance of thunderstorms mainly along the coast late
on Monday, along with locally breezy winds, with the highest winds
near the coast and the North Interior. With multiple wet systems
in a short amount of time, decent rainfall will lead to rising
rivers across the area, especially the Skokomish River in Mason
County. Refer to the .Hydrology section below for more information
on possible river flooding.

Another system will impact the area on Tuesday-Wednesday, with
more lowland rain, and lower snow levels down to around 3500-4000
feet with accumulating snow at the higher peaks and near the
passes likely. Active weather will continue through the long term
period, with more bouts of rain for the lowlands and snow for the
mountains.

Mazurkiewicz

&&

.AVIATION...Southwesterly flow aloft develops today. Meanwhile, a
weak disturbance offshore is spreading some mid-level clouds over
the region. Therefore expect VFR conditions across most of the
terminals through the day. However, given the light wind and
residual low level moisture, will likely see some fog form in
the more prone locations including KOLM and KPWT through around
daybreak. Any fog that does form should scatter relatively quickly.
Another passing front will spread some light precipitation into the
region by late in the TAF period.

KSEA...VFR conditions prevail with some increasing mid-level clouds
through the day. Surface winds southerly and light through the day.
A weak front arrives Friday night, with a return of lower ceilings
into MVFR range and some light rain expected.

&&

.MARINE...A warm front will move into the coastal waters and stall
out, with only a few occasional gusts to 15-20 kt. The bigger impact
may be seas, building to 9-10 ft over the outer coastal waters this
morning. As a result, a small craft advisory has been issued for
these zones. The next disturbance, a weak cold front, will push
through the waters on Saturday. However, we`ll see a much stronger
frontal system that will bring a return of widespread advisory winds
(with the potential for some gales - current guidance suggest around
a 40-50% chance over the coastal waters and around the eastern
Strait of Juan de Fuca. Seas over the outer water are likely to
hover around 10 ft today and tonight as a northwest swell enters the
waters. Seas will likely build back above 10 ft at times through the
weekend. However, a much larger increase is expected around Monday
as a stronger system approaches and brings a sharp increase in seas
over the coastal waters to around 18 to 20 ft.

&&

.HYDROLOGY...A weakening frontal system will move through Western
Washington later tonight and Saturday for increasing rain,
although at this time QPF amounts are expected to remain lighter.
A more significant chance of precipitation is expected Sunday
through Monday, and again on Wednesday as an active weather
pattern returns. At this time, the Skokomish River is the only
river forecasted to rise into flood stage, and potentially
moderate flood stage during the middle of next week. For other
rivers, significant rises are expected and flooding could be
possible, but at this time is not forecasted. 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 monitor river levels during this
period.

JD/Mazurkiewicz

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 5 AM PST Saturday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

&&

$$