Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
212
FXUS66 KSEW 230309
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
803 PM PDT Sat Aug 22 2026
.SYNOPSIS...An upper low offshore will move inland tonight and
weaken through Sunday. Upper ridging builds into the Pacific
Northwest Monday and Tuesday for warmer, dry conditions. An
upper low will approach the region midweek for increasing
onshore flow and light precipitation chances. Onshore flow into
late week will continue cooler conditions into next weekend.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
Thunderstorm activity has largely quieted over western Washington
this evening, mostly over the Strait and moving northward. This
northward progression has also allowed the inherited Red Flag
Warning to expire earlier this evening. Inherited forecast remains
on track and no updates needed this evening. For additional forecast
details, please refer to the Previous Discussion section below.
18
From Previous Discussion...An upper low continues to meander towards
the Western Washington coast this afternoon. A complicated pattern
exists with onshore flow at the surface and continued southerly flow
aloft. Scattered thunderstorms occurred this morning, especially
over the Cascades. Increasing daytime heating and further
destabilization has resulted in additional thunderstorms this
afternoon over the North Cascades. In addition, we continue to
monitor the threat for localized severe wind gusts (>58 MPH) this
afternoon and evening with any stronger thunderstorm over the North
Cascades. Elsewhere, POPs remain lower, but a few isolated showers
and thunderstorm may exist King County northwards. The upper low
will move inland and transition to an upper trough tonight into
Sunday. Lingering light rain will continue at times over the
Cascades into Sunday with widespread cloud cover into Sunday as
well. Temperatures will remain near to slightly cooler than normal
through the weekend due to the presence of the upper troughing.
An upper ridge slowly builds over the Pacific Northwest
beginning Sunday night resulting in drier, warmer conditions on
Monday. Surface flow also becomes more northerly, with a slight
east component Monday night. This may allow for smoke transport
from ongoing wildfires in BC and Eastern Washington towards
Western Washington early next week, which continues to be
monitored. Otherwise, highs will warm into the mid 70s to mid
80s on Monday.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...The upper ridge remains
over the Pacific Northwest on Tuesday, with the ridge axis
focused over the Intermountain West. For this reason, Tuesday
will be the warmest day of the week, with highs across the
interior in the 80s and low 90s in the Cascade Valleys,
resulting in areas of Moderate HeatRisk. An upper low will
approach the Pacific Northwest offshore by Wednesday leading to
increasing onshore flow and cooler conditions. Precipitation
chances also increase Wednesday into Thursday associated with
this system, and will need to monitor thunder potential over the
Cascades (although current probabilities are less than 10%).
Ensembles suggest the influence of troughing continues into
Friday with onshore flow and temperatures a few degrees below
normal. JD
&&
.AVIATION...
An upper level trough will continue to move north with south flow
aloft transitioning to west/northwest as it moves east. VFR decks
remain this evening across most terminals, with lower stratus along
the coast/just offshore. Additionally, thunderstorms continue to
remain in the Strait of Juan de Fuca area as they slowly move north
into Victoria this evening. Brief gusty winds and lightning are the
main threats with this area of convection. The threat of thunder
will diminish after sunset, although showers will continue through
tonight across the north interior (affecting BLI). Stratus from the
coast will fill into the interior overnight, reaching Puget Sound
terminals by around 12Z. Model guidance holds onto the stratus past
18Z (likely 19-21Z). Probabilities favor MVFR for most, with the
coast holding onto a 40-60% chance of IFR/LIFR conditions. Wind
gusts will diminish tonight for most except the north interior out
of the southwest around 5 kt. Winds Sunday will shift from the
southwest in the morning, to the northwest in the afternoon/evening
4-8 kt.
KSEA...VFR through the evening with decks remaining overhead. MVFR
stratus remains likely to arrive around 12Z, and remain through 19-
21Z. Southwest winds 4-8 kt tonight becoming northwest Sunday
afternoon.
HPR
&&
.MARINE...
A few areas of showers and thunderstorms will continue in the Strait
of Juan de Fuca area through dusk, with showers continuing in the
north interior tonight, and breezy winds diminishing by Sunday
morning. The low will track inland on Sunday. High pressure will
rebuild over area waters on Sunday and remain over the area through
Tuesday. A weak frontal system will move across the waters midweek.
Then high pressure will rebuild over the waters late in the week.
Diurnal westerlies in the Strait of Juan de Fuca evening the next
few days.
Seas 3 to 5 feet through the majority of next week.
29/HPR
&&
.FIRE WEATHER...
Showers and thunderstorms wrapping up this evening. As the upper
level low passes through tonight and early Sunday, showers and
isolated showers may still be possible, but the probabilities for
thunderstorms will be significantly reduced and as such may not
warrant any additional headlines. Will leave that for overnight
shift to evaluate with latest model data. Upper level ridge building
in later Sunday. Brief low-level offshore flow possible on Monday as
thermal trough builds along the coast before pushing inland
overnight into Tuesday. Another upper level trough arriving in the
middle of next week increasing the chances for more showers and the
potential for thunderstorms. Upper-troughing may linger into Friday.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion