Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
750
FXUS66 KSEW 032305
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
405 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/...
Latest satellite imagery shows northeasterly flow aloft continuing
to advect smoke across Western Washington, resulting in hazy
conditions aloft. Northwesterly surface winds has limited near-
surface smoke transport today. Temperatures this afternoon expected
to peak in the upper 60s along the coast and 70s to low 80s in the
interior.
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...
Northerly flow aloft becoming more northwesterly by this evening and
remaining that way for the remainder of the TAF period. Surface
winds generally north to northeasterly, although some isolated
terminals /BLI, HQM/ are seeing westerly winds. BLI is expected to
shift more northerly this evening while HQM will remain westerly
until Tuesday afternoon. Speeds this afternoon and early evening
expected to range 8-12 kts with occasional gusts up to 20 kts
possible. This evening and tonight, speeds expected to ease
somewhat, ranging 5-10 kts before becoming more light and variable
overnight. Winds will return to 8-12 kts by late morning and the
rest of the TAF period.
VFR conditions area-wide this afternoon with mostly clear skies.
Smoke from nearby wildfires in both Canada and eastern WA will
remain aloft today, 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 afternoon
ranging 8-12 kts with occasional gusts up to 20 kt possible. Speeds
easing to 5-10 kts tonight and remaining that way into Tuesday as
direction shifts more north to northeasterly.
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