Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
120
FXUS66 KSEW 040251
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
750 PM PDT Mon Aug 3 2026
.SYNOPSIS...
Dry and warmer conditions as an upper level ridge offshore moves
inland Wednesday and Thursday. A thermally induced trough will
develop tonight and remain over the region through Wednesday,
resulting in northeasterly winds advecting smoke to Western
Washington. The ridge will push eastward late Thursday. Smokey
conditions should improve by the end of the week with increased
onshore flow. Cooler temperatures favored for the weekend.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Current satellite showing smoke aloft over much of W WA this
evening, with the exception of the Olympics. The main impact this
evening and most of tonight is expected to be some haze for most
locations. A side benefit to this smoke aloft is that it kept
daytime high temps anywhere from 1-4 degrees shy of what was
forecast. A consideration for future shifts will be if persistent
smoke will further affect temps as the current warming trend
continues. That said, forecast remains on track with no need for an
evening update. For addtional forecast details, please refer to the
Previous Discussion section below. 18
From Previous Discussion...An upper level ridge continues to sit
offshore this afternoon. It will begin to slowly push inland
midweek. A thermally induced trough is expected to develop tonight
along the coast and remain in place through midweek. As a result,
surface winds will shift north-northeasterly on Tuesday and smoke
will descend to the surface from British Columbia and Eastern
Washington fires. A gradual warming trend is expected through the
latter part of the week. However, with smoke filtering to the
surface, it presents a challenging forecast as to how it will affect
high temperatures. The current forecast has high temperatures in the
70s along the coast and 80s in the interior on Tuesday. As for
Wednesday, temperatures are forecasted in the 70s for the coast and
80s to 90s in the interior. It is possible that observed
temperatures are lower than what is in the forecast. In addition,
there is uncertainty as to how far west surface smoke will reach.
With increasing temperatures, Minor to Moderate (Seattle-Tacoma
Metro & Southwest Interior) HeatRisk on Tuesday. More widespread
Moderate HeatRisk is expected by Wednesday.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Long-term guidance is in good agreement that the ridge axis directly
over Western Washington will start to push eastward later on
Thursday, along with the thermal trough. This will lead to
increased onshore flow Thursday night, continuing into next
week. Increased onshore flow should improve smokey conditions
over the region. However, there is uncertainty as to how quickly
conditions will improve. Another hot day expected on Thursday
for the interior with temperatures in the mid 80s to 90s. As for
the coast, cooler temperatures in the upper 60s to low 70s.
A weak upper level trough and cooler temperatures are favored
this weekend.
29
&&
.AVIATION...
Northwesterly flow aloft this evening and remaining that way for the
remainder of the TAF period. Surface winds generally from the north
with some variation to the NE or NW depending on location. Most
terminals expected to retain this direction with a slight favoring
of NE for much of the TAF period, although some will go light and
variable overnight. Speeds mostly 4-8 kts into Tuesday morning
before increasing somewhat in the afternoon to 5-10 kts.
VFR conditions area-wide this evening and expected to persist for
much of the TAF period. Smoke from nearby wildfires in both Canada
and eastern WA will remain aloft this evening, but could start
making its way to the surface as early as overnight tonight, but
latest model data suggests this may hold off until Tuesday as the
atmosphere begins to mix better. Currently, the only impact expected
is some haze this evening and tonight. Additional impacts are
possible tomorrow as smoke mixes down closer to the surface, which
will likely impact visibilities. It is important to remember this
smoke may limit both horizontal and slant-range visibilities...and
thus experienced vis may be less than what is being reported in obs.
KSEA...VFR throughout the TAF period. Elevated smoke will increase,
becoming more surface-based Tuesday. This may result in vis
reductions. To anticipate this, have included HZ after 18Z Tuesday
afternoon with a more impactful TEMPO for the afternoon hours
reducing vis to 5SM. This could be more, depending on daytime
mixing, but feel this is a good starting point for future
amendments/updates. North to northwesterly winds this evening before
favoring more northeasterly overnight and Tuesday morning. A slight
turn to northerly is expected in the afternoon. Speeds 5-10 kts
tonight and remaining that way into Tuesday.
18
&&
.MARINE...
A strong area of high pressure will remain offshore throughout
midweek as a thermally induced low pressure expands northward along
the interior coast. Northwesterly winds will prevail across the
coastal waters this week. With increasing confidence, a small craft
advisory has been issued for the southernmost coastal water zones
this afternoon. Breezy conditions briefly expected Tuesday morning
across Puget Sound, however winds should remain below small craft
thresholds. The surface trough is expected to push inland on
Thursday, resulting in increased onshore flow across the waters.
Small craft winds are possible through the Strait of Juan de Fuca as
early as Thursday evening, continuing into the weekend. Latest
guidance suggests the strongest winds will be on Friday, with a 70-
85% chance of small craft winds and 25-40% chance for gales. Another
strong push expected on Saturday, with a 65-80% chance for small
craft winds and 15-20% chance for gales.
Seas expected to remain below 10 ft for the majority of week and
will trend toward 10 feet toward the weekend. Steep seas possible
Tuesday evening at times over the coastal waters. 29
&&
.FIRE WEATHER...
A warming and drying trend will continue across western Washington
through much of the week as a high pressure ridge builds offshore
and a surface thermal trough builds northward along the Pacific
coast. Several days of drying and warming will drive minimum
relative humidity values to near critical levels, especially in the
western Cascades and Olympics where humidities may reach critical
values as low as the teens to upper single digits by Wednesday and
Thursday. While no significant wind or instability is expected
through the week, maximum caution should be emphasized.
The thermal trough will shift inland on Thursday with the arrival of
a frontal system late Thursday into Friday. Some uncertainty remains
over potential instability and incoming wind in combination with the
movement of the thermal trough which may briefly promote fire
growth. Increased onshore flow by Friday is expected to bring cooler
temperatures and increased moisture with healthier humidity
recoveries.
In addition, north to east winds throughout the week will continue
to bring in wildfire smoke from eastern Washington and British
Columbia. This may cause localized impacts to fire operations at
times.
15
&&
.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 Tuesday 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