568
FXUS66 KSEW 150258
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
800 PM PDT Mon Jul 14 2025

.UPDATE...Clouds from an afternoon convergence zone over the central
and south Puget Sound have since pushed southward, thinning as they
go. This leaves much of the CWA under generally clear skies.
Inherited forecast remains on track.

&&

.SYNOPSIS...Dry and much warmer conditions will return Tuesday
through Thursday, widespread moderate HeatRisk levels expected
throughout the interior of Western Washington. In addition, elevated
fire weather conditions are expected with possible critical
conditions for some areas during this period. More moderate
temperatures are expected late in the week and into the weekend.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...Temperatures
this afternoon running 10 to 15 degrees cooler than yesterday -aided
by the stronger onshore flow and mid level clouds that have settled
over the interior. This will translate into near normal overnight
temperatures with a few lingering clouds especially during the
evening.

The cooldown will be shortlived as upper level heights build quickly
behind todays weak system as it moves into the Intermountain area
overnight. Low level onshore flow also weakens and becomes
northeasterly as a thermally induced surface trough works northward
along the Oregon coast. Hires models - including the ensembles
consistently show the surface trough remaining over the Oregon and SW
Washington coast, if not slightly inland. This will help keep the low
level more northerly than easterly for much of Western Washington.
Nonetheless, highs in the interior will reach the 80s to low 90s on
Tuesday, with widespread 90s on Wednesday - leading to widespread
moderate HeatRisk levels over much of the interior. The immediate
coast will remain in the 60s with a sharp gradient to 70s and even
80s a few miles inland. Overnight lows will also remain relatively
warm especially Tuesday night into Wednesday morning, with many
areas showing 50 to 70% probabilities of lows remaining in the low
60s. These odds are higher for the metro area from Tacoma to Seattle
where the odds are over 90%. In addition, the N/NE winds aloft which
may bring Canadian wildfire smoke into western WA Tuesday remaining
generally aloft except for higher elevations in the north Cascades.
The flow will turn westerly on Wednesday for less smoke intrusion
over the westside.

.LONG TERM /THURSDAY THROUGH MONDAY/...The pattern begins to
transition Thursday with weaker low level onshore flow bringing
cooler conditions to the coast Thursday- Friday. Warmer conditions
will likely linger in the interior, especially the metro area where
high temperatures will remain warm and in the 80s. More developed
onshore flow this weekend looks to finally brings temps back to
normal - but remaining dry.

&&

.AVIATION...Northwest to northerly flow aloft as an upper level
ridge remains offshore. Widespread VFR conditions this evening and
remaining in place for most terminals for remainder of TAF period.
Only exception may be HQM, as weak westerly push might be enough to
bring in marine stratus for MVFR conditions overnight. Confidence is
shaking in this outcome however as stratus off the coast is thinning
as it retreats to the south. Majority of terminals seeing northerly
winds with speeds on average 5-10 kts. These speeds expected to ease
overnight, mainly in the 3-8 kts range. While some terminals remain
northerly into Tuesday, other will shift more easterly, such as OLM,
CLM, and PWT between 15-18Z.

KSEA...VFR conditions and northerly winds for the TAF period. Wind
speeds this evening still running 8-12 kts before easing to 4-8 kts
by 06Z. Speeds pick back up to 8-12 kts Tuesday afternoon by 18Z.

18

&&

.MARINE...High pressure remains offshore giving way to onshore flow
across the area waters. A subtle shift offshore will occur on
Tuesday before onshore flow returns on Wednesday with the potential
for SCA winds through the strait. Have to monitor the inner coastal
waters as well for small craft northerlies for both Tuesday and
Wednesday. A Small Craft Advisory will continue for the outer
coastal waters for elevated winds and steep seas into early Tuesday
morning.

Coastal seas 8 to 10 feet and will generally remain through the
first half of the week, falling to 6 to 8 ft through the latter half
and 4 to 6 ft by the weekend.

McMillian

&&

.FIRE WEATHER...As high pressure returns to the area beginning
Tuesday, expect to see afternoon RH values dip down critical
thresholds Tuesday afternoon with a thermal trough building north
over the Cascades. While some uncertainty remains with respect to
how far north and west this builds, expect to see at least some
light east component to the surface winds near the Cascade gaps in
zone 659 and portions of 657 and 658. As such, a Fire Weather Watch
for these areas remains in effect. Confidence is lower in seeing
more widespread easterly wind, but this may serve to further reduce
RHs. Additionally, depending on the placement of the thermal trough,
expect to see a deeper mixed layer and increased instability over
the Cascades with mixing heights potentially rising into Wednesday.
While confidence in the specific timing of elevated fire weather
concerns is still lower, the mid week period will have the worst of
the fire weather conditions for existing incidents and for the
potential for any new ones were to begin. Looking ahead to the end
of the week, expect conditions to moderate but remain warmer and
drier than normal. However, forecast guidance continues to exhibit a
large range of potential scenarios that leave confidence lower than
normal. Cullen/JBB/18

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Fire Weather Watch from Tuesday morning through Wednesday
     evening for Black Hills and Southwest Interior Lowlands-
     West Slopes of the Central Cascades Generally above 1500
     Feet-West Slopes of the North Cascades Generally above 1500
     Feet.

     Heat Advisory from noon Tuesday to 10 PM PDT Wednesday for 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-Lowlands
     of Western Whatcom County-Middle Chehalis River Valley-
     Northern Hood Canal-Olympia and Southern Puget Sound-
     Shoreline / Lynnwood / South Everett Area-Southern Hood
     Canal.

PZ...Small Craft Advisory until 5 AM PDT Tuesday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From Point Grenville To Cape Shoalwater 10
     To 60 Nm.

&&

$$