Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
856
FXUS66 KSEW 260309
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
809 PM PDT Tue Aug 25 2026
.SYNOPSIS...
Dry and warm conditions will peak this afternoon ahead of a pattern
change tonight that will bring the return of onshore flow, cooler
temperatures, and chances for precipitation to the area.
Thunderstorm chances increase Thursday across the Olympics, northern
Interior, and North Cascades. Upper level troughing will continue to
influence the region over the weekend, maintaining cooler and
cloudier conditions across western Washington.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
Latest satellite imagery shows the the marine layer along the
coastline slowly pushing inland this evening. Otherwise, no
major updates to the forecast this evening.
Upper level ridging over the Intermountain West will maintain
southerly flow aloft across western Washington today, bringing
the warming and drying trend to a peak. Temperatures across the
region are well on their way to reaching the mid to upper 80s,
with some areas in the Cascade foothills and valleys reaching
the lower 90s. This corresponds to widespread Moderate (orange)
HeatRisk across the lowlands from the Puget Sound metro areas
northward through Bellingham, with some pockets of Major (red)
HeatRisk in the Cascade valleys. Along the coast, low level flow
has switched to onshore, bringing in cooler and more moist air
under the marine layer with highs closer to the mid 60s to lower
70s.
Onshore flow will continue to increase throughout the afternoon and
evening today, bringing in a push of cooler and more moist air. This
will also help to scour out any lingering haze from wildfire smoke.
The onshore flow will bring a return to cooler and more seasonable
temperatures, morning clouds, and afternoon sunshine to most areas
over the next several days across western Washington, though areas
along the coast may have a hard time breaking out of marine stratus.
Continued troughing will also bring increased chances for light
precipitation and isolated thunderstorms, though rainfall amounts
look to be minimal through the week.
An upper level trough will swing inland to the north on Thursday,
bringing the highest chances for thunderstorm activity over the next
week. The Olympic Peninsula and North Cascades will see the best
chances for isolated thunderstorms on Thursday with potential rain
shadowing over the northern interior and islands, though storm
chances peak at around 10-20%. Storms and rain showers with this
system are expected to bring light rainfall amounts of generally up
to a tenth of an inch of rain to the region.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Ensembles continue to show high chances for troughing to remain over
the Pacific Northwest into next week, bringing continued chances for
light rain and isolated thunderstorms over higher terrain. The
details remain fairly uncertain at this time, but seasonal
temperatures, cloudy mornings, and afternoon sun breaks are expected
through early next week.
15
&&
.AVIATION...
Southerly flow aloft will persist as upper level ridging continues
to move eastward. Marine stratus will persist along the coast
through this evening with MVFR to IFR conditions continuing. Smoke
and haze will continue aloft, mainly affecting slant- wise
visibility in the mid and upper levels. The back edge of the smoke
moves east of the Cascades tonight. Winds remain SW 5 to 10 knots,
with gusts up to 20 knots through around 06Z Wed for terminals west
of the interior.
Tonight, after 06Z, the marine push will make farther progress
inland. An extensive mix of IFR/MVFR ceilings and patchy fog is
expected to reach peak coverage around sunrise, then gradually erode
during Wednesday. Southwesterly winds will slowly east this evening
to around 5 kt or less by early Wednesday morning. Winds increase
again to around 5-10 kt during the day Wednesday.
KSEA...Patchy smoke at around 6000 ft agl is expected to push
eastward tonight. VFR will persist through this evening with SW
winds remaining at 5 to 10 knots. Onshore flow is expected to bring
a marine push late tonight into Wednesday morning, with stratus
beginning to develop around 10-12Z. MVFR ceilings remain likely from
13Z to around 17Z, with clouds lifting and scattering to VFR, which
will follow through Wednesday evening.
62/HPR
&&
.MARINE...
Surface high pressure will continue over the coastal waters today
with a thermal trough along the coast shifting inland this afternoon.
Increasing onshore flow tonight and into Wednesday will result in
small craft westerlies through the Strait of Juan De Fuca.
Weak systems crossing over the coastal waters will continue the
onshore flow pattern through the remainder of the week with
continuous pushes each afternoon and evening down the Strait of Juan
De Fuca. Chances for isolated thunderstorms over the waters
increases on Thursday with the passage of a frontal system, which
may locally produce gusty outflow winds and lightning.
Seas generally remain around 4 to 6 feet through the weekend.
Mazurkiewicz/15
&&
.FIRE WEATHER...
Elevated fire weather concerns will continue into the afternoon
today as easterly flow promotes additional drying and very low
relative humidities in the mid to lower 20s along the western
Cascade gaps.
A pattern change on track for later today into Wednesday will bring
the return of moist onshore flow, excellent overnight relative
humidity recoveries, cooler temperatures, and chances of light
precipitation to western Washington at times through much of the
second half of the week. Overall, expect upper level troughing to
help mitigate fire weather concerns for most areas. The exception
will be in any isolated thunderstorm activity through the week,
particularly on Thursday across the mountains and northern interior.
While the exact details on thunderstorm activity remain uncertain at
this time, lightning from any storms that do develop may lead to new
fire starts mainly over the mountains and gusty, erratic outflow
winds could impact ongoing fires within the vicinity of any storms.
14/15
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 2 AM PDT Wednesday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
&&
$$
NWS SEW Office Area Forecast Discussion