865
FXUS66 KSEW 020335
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
735 PM PST Mon Dec 1 2025

.SYNOPSIS...Generally quiet weather is expected through
Wednesday night or Thursday. The door will open to a series of
weather systems beginning Thursday and continuing into next
week. Initially the concerns will be gusty winds and the
potential for coastal flooding, then transition to a river flood
threat with a continued coastal flood threat as we move through
the weekend into next week. Active weather is likely to
continue through at least the first half of next week.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...Widespread
clouds this evening with areas of light precipitation as a
frontal system moves across Western Washington tonight. No major
forecast updates this evening, previous discussion below.

Generally quiet conditions are expected in the short term. A
weak frontal will push through tonight into early Tuesday
bringing with in some light precipitation with little impact
expected. A ridge will nose into the region Wednesday, keeping
the area relatively dry. Patchy fog will be possible each
morning.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...By Thursday, weak waves
moving over the top of the ridge could begin to increase
precipitation chance Thursday, but the ridge breakdown is more
likely to occur Friday. Beginning Friday, the door will open to
periods of moderate to heavy precipitation associated with
moisture plumes originating from the subtropics. While each of
these periods alone appear unlikely to cause issue, the
successive nature could result in a increased risk of flooding
as early as this weekend, but perhaps more likely by early next
week. In addition, rainfall-driven landslide indices are also
approaching seasonal thresholds and by early next week the
landslide risk could become the highest yet seen this season.

In addition, hazards associated with coastal flooding and wind
will become elevated late this week, likely peaking late this
weekend or early next week. Currently, the coastal flood risk
appears to peak along the outer coast Thursday through Saturday
this week, but at this time, only appears to flirt with minor
flood thresholds. The concern is higher for the inner coast of
the Puget Sound and Salish Sea from Friday into early next week.
Current models indicate multiple days of water levels well above
minor flood stage, and a few locations (particularly Cherry
Point and Friday Harbor) flirting with moderate or higher flood
levels. The actual level of impact will strongly depend on the
overlap of low pressure and elevated winds which are a challenge
to nail down at this lead time.

Looking out beyond the next 7 days, the Climate Prediction
Center has included a moderate (40-60%) chance of hazardous
rain, high elevation snow, and winds continuing through December
10.
-Wolcott-

&&

.AVIATION...Northwest flow aloft will continue with an upper
ridge positioned well offshore. A weak frontal system will
continue to move across Western Washington into early Tuesday.
Widespread mid clouds this evening with light precipitation at
times. Cigs are slowly lowering to MVFR for some locations, and
will continue to do so tonight. MVFR/IFR cigs expected after
07/08z for most locations, which will continue through Tuesday
morning. Cigs will slowly lift Tuesday afternoon, but likely
remain MVFR for a portion of Puget Sound due to abundant surface
moisture and light flow. Primarily light south winds into
Tuesday, with more of a northerly component Tuesday afternoon.

KSEA...VFR conditions this evening will become MVFR generally
around 07-08z. We have increasing confidence in IFR cigs as well
Tuesday morning, particularly between 12 to 19z with abundant
surface moisture. Cigs are expected to slowly lift into MVFR
Tuesday afternoon, but likely remain MVFR into Tuesday evening.
Light south winds will become more VRB Tuesday morning. Winds
are expected to transition north between 18-20z. JD

&&

.MARINE...A weak frontal system will cross the Pacific
Northwest tonight into Tuesday resulting in small craft winds
beyond 10 nm offshore. Seas will also increase from 4-6 ft
Monday to 9-12 ft Tuesday through Wednesday. Benign conditions
are expected behind this system, with light winds, and seas
returning to 4-6 ft. A stronger system Friday through the
weekend may bring small craft advisory level winds to the
coastal waters, and a few of the north interior waters. There is
also a medium chance at this time for gale winds in the Strait
of Juan de Fuca. Seas will also increase to 9-13 ft with this
system Friday through the weekend into early next week.

Wolcott/HPR

&&

.HYDROLOGY...A series of at least two (and potentially more)
atmospheric river events with subtropical origins is currently
expected to impact the area beginning roughly Friday and
continuing through the weekend into early next week. Given the
lead time, there is still quite a range of potential outcomes,
but there is at least a chance of a significant flood event
beginning as early as this weekend, but more likely early next
week. Based on the latest HEFS guidance, the median (50th
percentile) forecast would result in only a few rivers reaching
action stage, while the higher end scenarios indicate the
potential for significant flooding. The 90th percentile
(reasonable high end) in particular indicates the potential for
a few rivers to reach major flood stage. These higher end
scenarios would also bring with it an elevated rainfall-driven
landslide risk.
-Wolcott-

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from midnight tonight to noon PST Tuesday
     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.

&&

$$