876
FXUS66 KSEW 132246
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
346 PM PDT Wed Aug 13 2025

.SYNOPSIS...A passing disturbance has brought cooler, marine air
to the region today. Increasing chances of widespread rain across
the region Thursday night into the weekend as a stronger weather
system moves across the area. Lingering showers will taper on
Sunday for a drier start to next week.


&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...Temperatures are 10 to 20
degrees cooler this time today compared to yesterday. Increased
onshore flow has poured cool, moist - marine air into W WA as the
natural AC is in full effect. On satellite, westerly flow off the
PAC is well apparent as marine stratus hugs the coast and Olympics.
Smoke from the Bear Gulch fire has even made its way as far east
as Montana this afternoon as an Air Quality alert remains in
effect for Mason County until Friday morning. For tonight, mostly
dry conditions but patchy drizzle could squeeze out of developing
marine stratus. Hi- Res guidance is signaling weak convergence
over King/Snohomish counties as well. Overnight lows will range
between the mid 50s to near 60 F.

A cloudy start to the day on Thursday as we remain entrenched
within the marine layer. Some degree of clearing is possible into
the afternoon for the interior however, the next disturbance will
arrive at the coast with more widespread clouds and rainfall
during the afternoon. This activity is slated to spread inland
overnight into Friday as a potent front ushers in ample moisture
with forecast PWAT values around 1.50-2.00" (200% of normal based
on climatology). While not unheard of, this anomalous disturbance
is worth noting as we`re well within our driest time of the year.
Along with moisture, favorable orographics are in place as a sharp
30-40 kt 850 mb jet serves as a conduit for decent rain
generation over the Olympics and Cascades. Moderate to heavy
rainfall is possible Friday through early Sunday morning with up
to 1.00-2.00" of rain in the forecast throughout the interior
lowlands. 2.00-4.00" of rain is in the cards along the mountains
and coast. Local rivers could see sharp rises this weekend as a
result of heavy rain; those recreating near rivers should remain
aware of the potential. Area burn scars may need monitoring
during this time as well.


.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Rain and showers will
decrease on Sunday and conditions gradually dry out. Can`t rule
out straggling showers here and there. A broad upper-low to the NW
of Haida Gwaii will help to keep temperatures not too far from
seasonal averages with highs in the mid to upper 70s throughout
the interior. The San Juans will likely remain in the lower 70s
with coastal areas in the 60s through midweek. Overnight lows will
bottom into the 50s.

McMillian


&&

.AVIATION...Westerly flow aloft as an upper level trough continues
to approach western Washington. A mix bag of conditions from VFR
to IFR out there as low clouds from this morning continue to
linger. The most notable is areas along the coast where lowered
conditions (MVFR/IFR) will likely remain as onshore flow
continues. Areas within the interior have mostly all rebounded to
VFR and will continue throughout majority of the evening. Westerly
winds this afternoon generally around 8 to 12 knots may have some
occasional gusts up to 20 kts, with wind speeds remaining somewhat
elevated throughout the evening. Ceilings will start to lower
later tonight to MVFR/IFR (08z-11z) as another batch of low
stratus spreads across the interior Thursday morning, with low
clouds lingering mostly likely throughout most of the afternoon.

Smoke from wildfires may also result in localized diminished
conditions in a few spots throughout this afternoon. While smoke
will largely remain aloft, some may mix down to the lower levels
from wildfire activity in Mason county. Smoke from Canadian
wildfires may also impact BLI at times.

KSEA...Low clouds at the terminal have broken up leading to VFR
conditions lasting throughout this afternoon. W/SW winds this
afternoon 8 to 12 knots with a few gusts up to 20 kts possible
throughout this evening. Ceilings will start to lower to MVFR
late tonight into Thursday morning (07z-12z) as another round of
stratus spreads inland. Winds will remain W/SW and hover around 5
to 10 knots Thurs morning.

Mazurkiewicz

&&

.MARINE...High pressure over the coastal waters will begin to
weaken into Thursday as a strong frontal system approaches the
waters. Onshore flow will increase later this evening into
Thursday, where westerly winds will increase through the Strait
of Juan De Fuca. A Small Craft Advisory is out for the Central and
Eastern Strait of Juan De Fuca - with occasional gusts up to gale
force strength being possible at times tonight. Winds will
generally be 20 to 30 kts, but again can`t rule out the occasional
gust or two.

The aforementioned frontal system will cross over the waters
Friday and Saturday for increased southerlies throughout most of
the waters. Southerly winds will become breezy especially over the
coastal waters and the interior waters of Puget Sound, which could
warrant additional headlines heading into the weekend. High
pressure will briefly build back early next week but will still
allow weak systems to pass over the waters.

Combined seas generally around 5 to 7 feet this afternoon will
gradually build upwards to 6 to 8 feet by Friday and through
Saturday. Seas will decrease by early next week to around 3 to 5
feet.

Mazurkiewicz


&&


.FIRE WEATHER...A trough will continue to produce onshore flow for
cooler temperatures and good to excellent relative humidity
recoveries. Rainfall chances increase beginning later on Thursday.
Confidence remains high that a frontal system will produce wetting
rains across the entirety of the region Friday into early Saturday.
Drier conditions and moderating temperatures will develop early next
week. 27



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

     Small Craft Advisory until 6 AM PDT Thursday 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.

&&

$$