049
FXUS66 KSEW 140347
AFDSEW

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

.UPDATE...No changes made to this evening`s updated. The previous
discussion is below along with an updated marine/aviation section.


&&


.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. Surface winds generally from the
southwest, although the western 3 terminals /HQM, CLM and OLM/
favoring more westerly and PAE seeing northerly due to push down the
Strait. Speeds generally 7-11 kts with some gusts up to 20 still
being observed this evening before easing slightly more into a 5-10
kts range.

Mostly VFR conditions out there this evening with a few isolated
patches of MVFR. Expecting another marine push overnight and as
such, cigs expected to erode down into widespread MVFR with isolated
patches of IFR possible in the 09-12Z time frame. While these low
level clouds are expected to linger throughout the remainder of the
TAF period, most terminals are expected to recover into low-end VFR
by 18-20Z, while locations more prone to lower cigs will have a hard
time breaking out of MVFR conditions.

KSEA...VFR conditions to linger this evening, gradually eroding
overnight before getting to MVFR around 12-14Z. Most guidance keeps
cigs around 2000-2500 ft, although some suggest dipping down to
around 1500 ft for a short period between 13-16Z. Will side with
higher cigs for now in TAF. Should see recovery back to low-end VFR
by 18Z. SW winds throughout the period with speeds remaining 7-11
kts.

18

&&

.MARINE....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 remains in effect for the
Central and Eastern Strait of Juan De Fuca. Winds will generally be
20 to 30 kts with occasional gusts up to gale force strength being
possible at times tonight. These gusts remain infrequent enough
where upgrading the inherited headline does not seem necessary at
this time. However, it is worth noting that wind speeds on the
Canadian side of the Strait have been routinely meeting gale at Race
Rocks Lighthouse. That ob certainly suggests that the situation
needs to be monitored, however no other station near there is
reporting these level of winds...most comfortably within the scope
of an SCA.

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 evening 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/18


&&

.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.

&&

$$