Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
911
FXUS66 KSEW 251822
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
Issued by National Weather Service Medford OR
1122 AM PDT Tue Aug 25 2026
.SYNOPSIS...
Upper level ridging over the Pacific Northwest will maintain warm
and dry conditions across western Washington today. An upper level
low approaching the region on Wednesday will bring the return
of onshore flow, cooler temperatures, and chances of precipitation
to the area. Upper level troughing will continue to influence
the region heading into the weekend, keeping conditions cooler
and cloudier across western Washington.
&&
.SHORT TERM /TODAY THROUGH THURSDAY/...
Upper level ridging, with the ridge axis positioned over the
Intermountain West, will continue to influence the area today,
bringing clear skies and warming temperatures to western
Washington. Winds remain easterly across the Cascades early
this morning and primarily out of the north across much of Puget
Sound, which has helped dry out the low levels, as well as
advect some smoke into the area from regional wildfires. Today
remains on track to be the warmest day of the week, with afternoon
highs expected to climb into the mid to upper 80s across much
of the interior and into the low 90s in the Cascade valleys.
This will reintroduce Moderate HeatRisk to the valleys as well
as the Everett-Seattle-Tacoma metro areas. Highs will remain
cooler along the coast and generally in the mid 60s to low 70s.
Winds will transition back to onshore later today, allowing for
areas of smoke to push eastward tonight.
A pattern change is expected later tonight into Wednesday as an
upper level low approaches the Pacific Northwest. This will
bring the return of onshore flow, more widespread morning
stratus, and cooler temperatures to western Washington. The low
will push inland into British Columbia on Thursday, swinging the
trough axis across western Washington. This will reintroduce
chances of showers to the area, primarily along the Olympic
Peninsula and for areas north of Everett, particularly over
higher terrain. While overall QPF amounts look to remain light
at this time, cannot rule out a few chances (between 10-15%) for
thunderstorm development along the Olympics and North Cascades
Thursday afternoon and evening. Afternoon highs will cool a few
degrees each day across the interior and look to top out in the
mid 70s to low 80s on Wednesday and low to mid 70s by Thursday.
Highs along the coast will be in the mid 60s both days.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Ensembles remain in good agreement with upper level troughing
remaining the dominant influence across the Pacific Northwest
heading into the weekend, with guidance suggesting another trough
moving southwards from British Columbia on Saturday. Onshore
flow will continue and chances of showers will remain possible
at times early in the weekend. A 10-20% chance of isolated
thunderstorms will also be possible Saturday afternoon and
evening. Uncertainty in the pattern increases by Sunday, though
ensembles hint at drier conditions across the area as a transient
ridge moves overhead ahead of a deepening trough offshore on
Monday. Temperatures throughout the long term look to trend
below normal, with afternoon highs expected to be in the mid 60s
to mid 70s across the area. Overnight lows will be in the upper
40s to mid 50s.
14
&&
.AVIATION...
Southwest to south flow aloft will persist as upper
level ridging continues to move eastward. Marine stratus will
persist along the coast through this afternoon with mainly IFR, and
some patches of LIFR. This stratus push is generally weaker than
previous mornings, so expect coverage to remain limited across the
interior. Smoke and haze will continue aloft, with the back edge
pushing east of the Cascades in the late afternoon/early evening.
Winds will be mainly southwest at 5 to 10 knots, with gusts up to 20
knots in the late afternoon/early evening.
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.
KSEA...Patchy smoke at around 6000 ft agl is expected to push
eastward and clear from the terminal around 23Z. 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 10Z.
MVFR ceilings are expected from 13Z to 17Z. VFR will follow through
Wednesday evening.
DW
&&
.MARINE...
Surface high pressure will continue over the coastal waters
today with a thermal trough along the coast 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.
Coastal seas generally remain around 4 to 6 feet throughout much
of the week.
Mazurkiewicz
&&
.FIRE WEATHER...
Warm and dry conditions are expected today, with upper level
ridging over the region. Easterly flow across the mountains
overnight will continue to promote additional drying near the
Cascade gaps, where relative humidity values are expected to
drop to near critical values in the low to mid 20s this afternoon.
Elevated fire weather conditions are expected for the Cascades
today as a result.
A pattern change late today into Wednesday will bring the return
of moist onshore flow, excellent overnight relative humidity
recoveries, cooler temperatures, and chances of 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 on Thursday and
Saturday, particularly across the mountains. 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 across the mountains and gusty, erratic outflow winds
could impact ongoing fires within the vicinity of any storms.
14
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 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