Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
452
FXUS66 KSEW 270301
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
800 PM PDT Wed Aug 26 2026
.SYNOPSIS...
An upper-trough will swing a couple of disturbances into the
region Thursday through Saturday. Brief ridging is in the offing
to begin next week but the pattern is forecast to reopen by
Tuesday as additional troughing takes aim.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
Inherited forecast remains on track this evening with no need for
forecast updates. For additional forecast details, please refer to
the Previous Discussion section below. 18
From Previous Discussion...An upper-trough offshore is analyzed in
the 500 mb levels. With it, marine stratus pushed well-inland today
but under diurnal heating it has since burned off and retreated back
to the coast this afternoon. Southerly flow aloft along with roughly
300-600 j/kg of CAPE has allowed for a slight chance (15%) of
thunderstorms today, primarily over the North Cascades. The threat
will greatly diminish this evening. For tonight, an additional round
of marine stratus will attempt to march inland as the upper-trough
shows progression. Overnight lows are forecast in the lower to upper
50s. Increasing rain showers along the coast and the Olympics into
the early morning hours on Thursday.
The aforementioned upper-trough will be squarely overhead on
Thursday. And with that, rain showers are forecast to become
more widespread. The North Cascades and Olympics will see up to
0.25-0.50" of precipitation during the day, elsewhere less than
0.10". Again, can`t rule out a slight chance (15%) of thunder for
the North Cascades and Olympic mountains. Wind gusts up to
20-25 mph are also expected with the strongest gusts across
Whidbey Island. We`ll be in between disturbances on Friday but
PoPs are favored to remain for the mountains. Convergence in the
850 mb levels is hinting at a developing PSCZ over King and
Snohomish counties Friday night. High temperatures for both
Thursday and Friday in the lower to mid 70s with overnight lows
in the 50s. Coastal max temps will maintain in the 50s.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Extended models in good agreement with upper level trough over
the area Saturday shifting east Saturday night. Temporary upper
level ridge moving through Sunday into the first part of Monday
before additional troughing and associated upper-lows swing
into the region Tuesday onward with cooler temps and more
widespread PoPs.
41
&&
.AVIATION...
VFR conditions continue across most of western Washington this
evening with a weak front just offshore of the coast. As this front
moves across the area tonight, that will bring in periods of MVFR to
IFR cigs across the area overnight into early Thursday morning. The
area most likely to see more steady low ceilings are KHQM and KCLM,
with the clouds being more transitory as a mid-level cloud deck
develops behind the front that will bring low-end VFR conditions
through much of the day on Thursday. A round of showers will also
develop over the Olympic Peninsula Thursday morning and over the
Cascades by the afternoon, though no impacts to area terminals are
expected. Chances for thunderstorms Thursday afternoon remain fairly
low (10-15%), so not confident enough to include at any terminals.
South to southwesterly winds around 5-10 kt will continue through
the evening tonight, decreasing overnight, and ramping up Thursday
with S/SW winds 5-15 kt and gusts up to 20 kt.
KSEA...VFR through the evening with south to southwest winds
generally 6 to 10 kt. MVFR ceilings are favored to develop once
again early Thursday morning around 10-12z and erode by 16-18z, with
a return to VFR with mid level clouds in the afternoon. Surface
winds will lighten overnight, then increase to as high as 15 kt
Thursday afternoon out of the southwest.
15/62
&&
.MARINE...
Southerly winds have picked up over the coastal waters today as a
weak frontal system crosses over the waters. This frontal system
will cause a westerly push through the Strait of Juan de Fuca
tonight, though winds are expected to stay just below Small Craft
strength.
Weak systems will continue to move over the coastal waters
through the end of the week, which will continue to provide pushes
down the Strait of Juan De Fuca, along with increasing southerlies
over the coastal waters. At this time, winds mostly look to remain
under small craft advisory, with increasing chances for Small Craft
westerly gusts through the Strait of Juan de Fuca Friday evening.
Chances for isolated thunderstorms over the waters also increase
Thursday, which may locally produce gusty outflow winds, areas of
low visibility, and lightning.
Coastal seas will remain around 4 to 6 feet through the weekend.
15
&&
.FIRE WEATHER...
Overall, the low level onshore flow producing good overnight
relative humidity recoveries and cooler daytime temperatures
will help ease fire weather concerns for the next few days.
Higher elevation slopes and valleys will remain somewhat drier
tonight. However, models indicate increased thunderstorm
probabilities for the afternoon/evening for today and Thursday.
There is a slight chance ( 15-25 percent ) of isolated
thunderstorms mainly in the north Cascades but it can`t be ruled
out around Mount Rainier. If there is a thunderstorm it will
not be accompanied by much rain and it could produce erratic and
gusty outflow winds impacting existing fires. In addition, the
lightning strikes pose a hazard and could lead to new fire
starts. JBB/Felton
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion