Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
137
FXUS66 KSEW 232127
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
227 PM PDT Sun Aug 23 2026
.SYNOPSIS...
An upper level trough will continue to move east of Western
Washington today. Drier and warmer weather Monday and Tuesday as
an upper level ridge builds over the Pacific Northwest. An
upper level low will approach the area around midweek, bringing
increasing onshore flow and cooler temperatures to Western
Washington for the second half of the week.
&&
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
An upper level trough continues to push across Washington this
afternoon. Partly cloudy skies this afternoon with high
temperatures in the low to mid 70s across the interior and mid
60s along the coast. An upper level ridge will build over the
Pacific Northwest on Monday, with the ridge axis east of the
Cascades on Tuesday. This will bring warmer and drier
conditions. The warmest day will be Tuesday. High temperatures
are expected to peak in the mid 60s/low 70s along the coast.
Across the interior, temperatures will climb into the 80s and
low 90s in the Cascade valleys. This will reintroduce widespread
areas of Moderate HeatRisk for the Everret-Seattle-Tacoma Metro
and Cascade valleys.
Additionally, surface flow will transition more northerly to
easterly Monday and Tuesday, resulting in wildfire smoke being
transported from nearby fires in British Columbia and Eastern
Washington into Western Washington. 29
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
There is good agreement between ensemble guidance that an upper
level low will approach the Pacific Northwest on Wednesday and an
upper level trough will settle over the region through late in the
week. This pattern will reinstate onshore flow across Western
Washington and bring cooler temperatures. Latest guidance has high
temperatures trending slightly below normal in the the low to mid 60
along the coast and low to mid 70s across the interior. Low
temperatures by the end of the week will trend towards the low
to mid 50s. Chances for precipitation look to return on
Wednesday and continue into the weekend. However, the latest
QPF amounts indicate precipitation will be light. While
thunderstorm chances remain at 10% or less, they could be a
possibility on Wednesday and Thursday as the upper level low
swings north into British Columbia and brings southwesterly
flow aloft over Western Washington. 29
&&
.AVIATION...
An upper ridge begins to build into the area tonight
through Monday, which will result in westerly flow aloft becoming
southwest on Monday. VFR cigs this afternoon with lingering areas of
MVFR mainly from PAE northwards. Clouds will slowly clear into this
evening. LIFR stratus will develop along the coast tonight. LIFR
cigs are also expected across the Strait of Juan de Fuca by early
Monday. Some uncertainty exists as to the extent of stratus around
central Puget Sound Monday AM. At this time, LIFR cigs are expected
to be confined to PAE and nearby river valleys. Otherwise, mainly
VFR elsewhere with a few high clouds on Monday with haze increasing
aloft late Monday with more of an E flow in the mid levels. Winds at
the surface will transition more north this evening, increasing from
the north Monday afternoon.
KSEA...VFR cigs this afternoon with continued mid level clouds. Cigs
will slowly clear into this evening. LIFR stratus will push inland
along the Strait of Juan de Fuca into early Monday. VFR conditions
are expected on Monday as the stratus is anticipated to remain north
of the terminal. There is approx. a 10% of LIFR cigs between 13-17z.
W/SW surface winds will transition to N/NW around 23-00z this
afternoon. Winds remain NE tonight at 5 to 9 kts. JD
&&
.MARINE...
High pressure continues to build over the Coastal Waters today
and will remain in place through Tuesday. North winds will
increase on Monday, particularly for the Coastal Waters and
Puget Sound. Will need to monitor for SCA wind gusts late Monday
afternoon through Monday evening for the Coastal Waters, with
current probabilities of SCA gusts around 40 to 70 percent
during this period. Onshore flow then increase Tuesday night
through Wednesday as a weak frontal system moves across the
waters midweek. This may result in SCA west winds through the
Strait of Juan de Fuca beginning Tuesday night. Onshore flow
then continues late in the week.
Seas around 3 to 5 feet may briefly peak towards 7 feet for the
southern Coastal Waters late Monday with increasing north winds.
This may lead to brief choppy waters with a period around 6 seconds.
Otherwise, 4 to 5 foot seas are expected Tuesday through much of the
week. JD
&&
.FIRE WEATHER...
An upper-trough has progressed off and away from western Washington
this afternoon. Conditions have trended drier but marine stratus has
remain well entrenched as shown by recent satellite imagery.
Guidance is in lock-step regarding a ridge building into the region
on Monday into Tuesday. A thermal trough will also snake along the
coast during this time, leading to a warm-up and drier conditions as
light offshore flow develops. Isolated areas of min RHs reaching
near critical thresholds are possible during this time in the
Cascades. Onshore flow then returns Tuesday night into Wednesday as
another upper-trough enters the region. Showers as well as the
chances for more thunderstorms are possible around the midweek
timeframe.
Less certainty in how the pattern will evolve towards the second
half of the week. Solutions are hinting at an upper-trough swinging a
pair of upper-lows into the region but there is disagreement in
exact timing and track. Nonetheless, below normal temperatures,
onshore flow and the potential for precipitation appears to be in
the offing towards the weekend.
41
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
NWS SEW Office Area Forecast Discussion