Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
327
FXUS66 KSEW 222213
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
313 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 /TODAY THROUGH MONDAY NIGHT/...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...The marine stratus continues to erode this afternoon
across the interior. VFR conditions expected for interior
terminals this afternoon, while MVFR will continue along the
coast. Another push of marine stratus will bring lowered
conditions to the interior terminals Sunday morning. Latest
guidance suggests majority of terminals will trend towards MVFR.
The coast and Strait of Juan de Fuca have the highest chances
(40-60%) for IFR ceilings tonight into Sunday morning.
Improvement expected in the afternoon for interior terminals and
minor/brief improvement along the coast. Shower and
thunderstorm activity has quieted down this afternoon across the
majority of the area. However, thunderstorm activity still
remains possible north of PAE towards BLI and across the North
Cascades. Thunderstorms will have the potential for frequent
lightning, gusty/erratic winds, heavy downpours, and reduced
visibility. Thunderstorm activity will dissipate tonight. Breezy
winds along the Strait of Juan de Fuca, Kitsap Peninsula, and
Northern Interior.
KSEA...VFR will prevail today. MVFR ceilings are likely Sunday
morning with another push of marine stratus. Improvement to VFR
after 21z. Southwesterly winds today through Sunday morning at 5-8
kt. Winds shift WNW Sunday afternoon at 5-6 kt.
&&
.MARINE...A weak surface low will continue to move across the
coastal waters today and 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. Today`s westerlies may approach 21 kt at times, but look
to overall remain below small craft criteria.
Seas 3 to 5 feet through the majority of next week.
Felton/29
&&
.FIRE WEATHER...Scattered showers and thunderstorms have been
observed so far today. Coverage has decreased into the afternoon but
additional storms are slated to develop, primarily for the North
Cascades where HREF guidance has 1,000 to 1,200 j/kg of surface
based CAPE modeled in concert with southerly diffluence aloft. As a
result, Red Flag Warnings remain for the North Cascades but
should be allowed to expire this evening as conditions trend
drier. 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...Red Flag Warning until 8 PM PDT this evening for West Slopes
of the North Cascades Generally above 1500 Feet.
Red Flag Warning until 5 PM PDT this afternoon for West Slopes
of the Central Cascades Generally above 1500 Feet.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion