634
FXUS66 KSEW 182256
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
356 PM PDT Fri Jul 18 2025

.SYNOPSIS...A broad upper level trough over Western Canada on
Saturday will drop down over Western Washington Sunday and Monday
for a chance of showers over the higher terrain. The trough
will move east Tuesday with a weak upper level ridge building
into Wednesday. Another trough will approach from the northwest
Thursday.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...A weak shortwave is
continuing to slide across western Washington this afternoon,
brining an area of thicker cloud cover and even some light
drizzle in spots as it moves south and east across the region.
Other than the cloud cover, the more notable difference today is
the significantly cooler conditions over much of the interior
with many locations still climbing through the upper 60s to
around 70 at this hour. Onshore flow will increase this evening
with some possible convergence bringing some enhanced clouds
over Snohomish County, but otherwise not much in the way of
weather impacts.

Morning clouds on Saturday likely linger a little longer as
onshore flow continues, but plenty of afternoon sunshine should
yield a Saturday afternoon similar in sun and temperature as
today for most. The next upper trough approaches closer into
Sunday, spreading additional cloud cover and perhaps a few hours
in the mountains. Otherwise, temperatures will remain similar on
Sunday.

.LONG TERM /MONDAY THROUGH FRIDAY/...For next week, we`ll see
the upper trough track across the area on Monday with a focus
for showers in the Cascades and an increased potential for a
thunderstorm or two in the North Cascades. Expect a slight
warming trend into midweek as the most likely evolution of the
pattern would see heights rising offshore and a weak ridge or
zonal flow over the region. This brings temperatures a couple of
degrees warmer each day into midweek. However, it`s worth
noting that the ensemble members begin to show a wider variety
of solutions in this time and confidence begins to decrease
later in the week.

&&

.AVIATION...Mid and high clouds will continue to move across the
area today, and VFR ceilings are expected to prevail for today for
the majority of terminals today. The exception being along the
coast, where MVFR conditions will continue this evening. In
addition, some terminals have been struggling to improve this
afternoon into VFR; however guidance hints at ceilings improving
after 22z-23z. Another push of marine stratus is expected Friday
morning, bringing widespread MVFR ceilings to the interior terminals
and IFR/LIFR ceilings along the coast. Terminals along the Kitsap
Peninsula and Strait of Juan de Fuca have a 20%-30% chance of IFR.
Improvement expected late Saturday morning into early afternoon into
VFR after 17z-20z.

Breezy conditions this evening along the coast, southern interior
(KOLM), and Strait of Juan de Fuca.

KSEA...VFR conditions expected today. Another push of stratus will
bring down ceilings to MVFR after 10z-12z, with improvement expected
after 17z-19z. S/SW winds at 6-8 kt throughout the TAF period.

29

&&

.MARINE...Broad surface ridging offshore and lower pressure inland
will maintain onshore flow over the waters into next week. An upper
level trough moving across the area today will enhance onshore flow
across the Strait of Juan de Fuca this evening, for which a Small
Craft Advisory has been issued for the Central and Eastern Strait.
The next push that may meet small craft criteria appears to be
Wednesday, with probabilities hinting at a 50%-70% of 21 kt or
higher. Otherwise, generally benign marine conditions, with seas
subsiding into the weekend and into next week to around 3-5 ft.

29

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Saturday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

&&

$$