063
FXUS66 KSEW 041034
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
333 AM PDT Sat Oct 4 2025

.SYNOPSIS...An exiting shortwave disturbance will allow for a chance
for scattered showers into this evening before dry conditions return
to western Washington. Upper level ridging will strengthen over the
Pacific and slowly move eastward Sunday and into the first half of
next week, warming temperatures over the area to above seasonal
normals. More active weather is possible for the second half of next
week.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...A weak shortwave will traverse
W WA today, bringing enough moisture to allow for a chance for
scattered showers. The terrain of the Cascades will be favored
somewhat, but drying conditions will start as early as late this
afternoon for the western half of the CWA with the eastern half
getting in on the action by this evening. Current radar supports
this thinking with little to no activity appearing at the time of
this writing while NBM solutions from 24 hours ago had Likely PoPs
/greater than 60 pct/ over much of W WA. Latest solutions,
thankfully, have backed off from this...and while PoPs may still be
inflated, they largely remain in the Slight Chance to Chance
category /generally less than 50 pct/...fitting the current
circumstances well enough. As alluded to above, some spots in the
Cascades may see PoPs around 60 pct...getting into low-end
Likely...but again, this seems fine as some terrain support could
justify that.

A building upper level ridge over the Pacific will be fully in
control of W WA weather by Sunday, as dry conditions resume and
warming trend starts. Highs Sunday will get in the mid 60s for most
of the interior lowlands, climbing into the upper 60s to around 70
for Monday.

18

.LONG TERM /TUESDAY THROUGH FRIDAY/...Models remain consistent with
regards to the start of the long term. The ridge continues to shift
eastward putting the ridge axis at least in E WA/ID panhandle. The
warming trend will culminate in the warmest temperatures of the
forecast period with interior lowlands getting into the lower to mid
70s. Unfortunately, Wednesday and beyond continue to remain
excruciatingly unclear as both deterministic and ensemble forecast
seemingly refuse to come to a consensus. There is agreement that a
troughy pattern sets up over the area and the only agreed upon
impact would be cooling temperatures down closer to seasonal
normals, returning daytime highs back to the 60s and allowing
overnight lows to dip down into the 40s. However, the track of the
upper level low associated with said trough will determine chances
for precip and amounts...and sadly solutions to this dilemma remain
unchanged from 24 hours ago: GFS sticking to its guns and kicking
the low out over the Pacific, keeping W WA dry-ish...ECMWF bringing
the low right into WA with typical autumn rains and ensembles
offering a lot of solutions in between. Like 24 hours ago, ensembles
do lean more toward ECMWF plan of a wetter solutions...but not too
wet as ensemble mean precip values have difficulty getting above one-
tenth of an inch. NBM does the best it can with this, offering
slight chance to chance PoPs for the area...as good a solution as
any at this time.

18

&&

.AVIATION...Light showers or drizzle remain possible early this
morning across Western Washington terminals as a weak frontal system
pushes through the region. Latest guidance still supports ceilings
lowering early this morning to LIFR (40-70% chance). In addition,
areas of patchy fog are possible early this morning at the
terminals. Improvement into VFR will be slow, with improvement
expected after 19z-22z. Guidance suggests HQM may see some brief
improvement to VFR between 21z-22z, but may remain MVFR into the
late evening hours of Saturday. Guidance hints at another round of
fog Sunday morning after 09z for the Kitsap Peninsula and southern
interior. Light to calm winds early this morning will transition
N/NW in the afternoon for most terminals.

KSEA...VFR early this morning with some low to mid cloud cover.
There is a 30-40% chance LIFR ceilings between 14z-18z with the
chance of fog development. Conditions will slowly improve Saturday
afternoon to VFR. Guidance hints that MVFR ceilings may return after
12z Sunday (35% chance). Light to calm winds early this morning will
become more NE after 13z at 3-4 kt. Winds will shift NW Saturday
afternoon at 6-9 kt, then becoming NE into Saturday night/early
Sunday morning.

29

&&

.MARINE...A weak front will continue to push through area waters
Saturday morning. Broad surface high pressure will build over the
waters Saturday night into Monday. A weakening frontal system may
move over the coastal waters on Tuesday, bringing the chance for
increased northwesterly winds that have a 30-50% chance of exceeding
21 kt. Seas will remain around 4-6 ft through the weekend and will
build to 6-9 ft on Tuesday.

29

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$