Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
323
FXUS66 KSEW 040914
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
214 AM PDT Tue Aug 4 2026
.SYNOPSIS...
Dry and warm conditions will develop as an upper level ridge
offshore moves inland midweek over a thermal trough along the
coast. Winds will turn offshore at times, bringing smoke from
fires in eastern Washington west into our region. Expect the
thermal trough and ridge to both weaken and shift east as early
as Thursday, with cooler temperatures by next weekend as a
trough passes through dry.
&&
.SHORT TERM /TODAY THROUGH THURSDAY/...
A ridge offshore in the Pacific is beginning to amplify a bit
in between two upper level lows/troughs, one over the northern
Great Plains/Upper Midwest, and the other over the north
Pacific. Down at the surface, it`s the opposite effect as MSLP
has a thermally induced surface trough along the coast
developing as conditions warm under the ridge. The combination
of the two will lead to warmer temperatures, and drier
conditions as the flow will turn offshore at times. This
offshore flow is also expected to bring in smoke from fires in
eastern WA over the next couple days. Soundings favor some of
the smoke to mix down to the surface as temperatures warm at the
surface, breaking the shallow inversion just aloft. For the
most up to date smoke and air quality information in your area,
please visit airnow.gov or your local air quality agency.
Besides smoke, heat will be the other factor to be aware of as
the ridge/thermal trough set up in the area. While smoke may
play a factor in holding temperatures during the day a few
degrees cooler, high temperatures in the upper 80s/low to mid
90s in the interior, with lows in the upper 50s to low 60s will
likely lead to a 2-3 day stretch of widespread Moderate (Orange)
HeatRisk across much of the interior. There is a 20-30% chance
of south Puget Sound urban areas seeing Major (Red) HeatRisk
Wednesday and Thursday. If planning to spend time outdoors next
couple days, consider taking frequent breaks indoors in a cooled
building as much as possible.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Ensembles favor keeping the warm pattern going through at least
Thursday as the ridge and thermal trough begin to weaken and
shift eastward. This will favor cooler temperatures going into
the end of the week and into the weekend, with HeatRisk becoming
predominately Minor (Yellow) by Saturday for the region. Highs
will still reach the upper 70s to low 80s for most of the
interior, but lows will likely improve into the mid and upper
50s. A trough will pass through next weekend, but there is no
signs of moisture at this time as this trough will likely only
produce a few clouds via weak onshore pushes. The smoke clearing
out will be dependent on how quickly the onshore gradient
strengthens with the trough following quickly behind the waining
ridge.
HPR
&&
.AVIATION...
Northwesterly flow aloft as upper level ridging continues
offshore. VFR conditions will continue at all terminals early
this morning and throughout much of the TAF period. Smoke from
the nearby wildfires in Canada and eastern WA has remained
aloft, with a growing possibility that it could mix down to the
surface this morning and into the afternoon. Smoke at the
surface will impact visibilities, likely seeing a range of
lowered vsbys generally around 4-SM 6SM at times this afternoon. It
is important to remember this smoke may limit both horizontal
and slant-range visibilities, therefore, experienced vsbys may
be less than what is being reported in observations. Otherwise,
we will see SKC and VFR for all terminals and smoke/haze likely
in most of the TAF sites, the exception likely being KHQM.
Light and variable winds will turn N/NE later this morning into
the afternoon around 5 to 10 knots.
KSEA...VFR conditions early this morning will continue through
the TAF period. Elevated smoke will increase later this morning
and afternoon, along with some smoke mixing down to the surface.
Have included the TEMPO group in the TAF showing decreased
vsbys generally around 4-6 SM at times this afternoon.
Vsbys may reduce further, depending on daytime mixing and how
much smoke is mixed down to the surface, which will have to
continued to be monitored in real time.
N/NE winds this morning 5 to 10 knots may slightly increase
this afternoon to 8 to 12 knots into the evening.
Mazurkiewicz
&&
.MARINE...
A strong area of high pressure will remain offshore through
midweek as a thermally induced low pressure expands northward
along the interior coast. Winds will decrease over the southern coastal
waters early this morning, allowing for the small craft
advisory to expire. Breezy conditions can be briefly expected
this morning across Puget Sound, however winds should remain
below small craft thresholds. A small craft advisory has been
issued for all the coastal water zones this afternoon and
evening due to choppy seas.
The aforementioned surface trough will shift eastward into
Thursday, resulting in increased onshore flow across the area
waters. Headlines likely throughout the Strait of Juan De Fuca
as increased westerlies filter through. At this time this push
likely will be small craft strength, but some guidance has been
hinting at a 30-40% chance of some gale strength gusts at times.
Seas 4 to 6 feet this morning increasing slightly this afternoon
to 6 to 8 feet, with the highest waves being in the outer
coastal water zones. With a 7 to 8 second swell, seas will
likely be choppy this afternoon and evening. Seas will remain
under 10 feet through the week.
Mazurkiewicz
&&
.FIRE WEATHER...
A ridge and thermal trough pattern remain on track to setup
across the region this week into Thursday, with a few days of
warm and dry conditions. Relative humidity (RH) values will
likely drop to critical levels into the teens (and perhaps a few
single digit values) as offshore flow helps dry things out. The
driest locations are the Cascades, and south interior, with
Wednesday and Thursday being the driest days. The good news with
these low RH values is that wind values likely remain light, not
leading to any critical fire weather conditions. However, the
dry relative humidity values will be more than enough to aid in
worsening fuels quality/conditions for fire starts. As the
thermal trough moves inland with the ridge Thursday/Friday,
there is some potential for increased instability in the
atmosphere for fire growth (though confidence is low). Onshore
increases by Friday, with another trough potentially passing
through dry into next weekend.
Additionally, smoke from fires in eastern WA is expected to
transit into our area, with some of it mixing down to the
surface next couple of afternoons.
HPR
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until 5 PM PDT Wednesday for Cascades of
Pierce and Lewis Counties-Cascades of Snohomish and
Northern King Counties-Cascades of Southern King County-
City of Seattle-Downtown Everett / Marysville Area-
Eastern Kitsap County-Eastside-Foothills and Valleys of
Central King County-Foothills and Valleys of Pierce and
Southern King Counties-Foothills and Valleys of Snohomish
and Northern King Counties-Foothills and Valleys of
Thurston and Lewis Counties-Foothills and Valleys of the
North Cascades-Lowlands of Lewis and Southern Thurston
Counties-Lowlands of Pierce and Southern King Counties-
Lowlands of Western Skagit and Northwestern Snohomish
Counties-Northern Hood Canal-Olympia and Southern Puget
Sound-Shoreline / Lynnwood / South Everett Area-Willapa
and Black Hills.
PZ...Small Craft Advisory until 3 AM PDT early this morning for
Coastal Waters From Point Grenville To Cape Shoalwater 10
To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
&&
$$
NWS SEW Office Area Forecast Discussion