Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
433
FXUS66 KSEW 041751
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
1051 AM PDT Tue Aug 4 2026
.UPDATE...
Based on the latest observations smoke is starting to mix down
to the surface this morning. Latest HRRR smoke guidance still
suggesting the heaviest smoke will impact the region this
afternoon, potentially reaching as far as the Olympic
Peninsula. Otherwise, forecast is on track for another warm
day with hazy skies. Although depending on smoke concentration,
it may inhibit daytime temps by a couple degrees.
29
&&
.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. Some
terminals starting to see visibility impacted this morning due
to smoke. Conditions are expected to gradually deteriorate this
afternoon, with the visibility decreasing generally to 4-6 SM.
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.
KSEA...Visibility impacts being reported at the terminal.
Expecting visibility to continue lowering this afternoon to
generally 4-6 SM. Visibility may reduce further, depending on
daytime mixing and how much smoke is mixed down to the surface.
Mazurkiewicz/29
&&
.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 from noon today to 2 AM PDT Wednesday for
Coastal Waters From Cape Flattery To James Island 10 To
60 Nm-Coastal Waters From Cape Flattery To James Island
Out 10 Nm-Coastal Waters From James Island To Point
Grenville 10 To 60 Nm-Coastal Waters From James Island To
Point Grenville Out 10 Nm-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