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735
FXUS66 KSEW 100933
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
233 AM PDT Thu Jul 10 2025

.SYNOPSIS...
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High pressure will build into the region into the
weekend and through the first half of next week, resulting in warm
and dry conditions across western Washington. The heat is expected
to peak next Wednesday, where temperatures could reach the low to
mid 90s across much of the region.
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.SHORT TERM /TODAY THROUGH SATURDAY/...
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Post frontal onshore flow
this morning will maintain cloudy skies as light shower activity
tapers off over the North Cascades and along the northern coast.
The marine layer will persist along the coast throughout the day
today but will burn off by the early afternoon across the interior
lowlands, giving way to mostly sunny skies as high pressure
builds offshore. The cloudy skies will limit high temperatures
along the coast today to the mid 60s, with temperatures peaking in
the lower 70s further inland.

A weak ridge will pass over the region on Friday, allowing
temperatures to rebound back into the lower 80s across much of the
lowlands. Weakening onshore flow will maintain cloudy skies along
the Pacific coast with mostly clear and dry conditions elsewhere.
Zonal flow will resume over the region on Saturday as a weak
disturbance passes over the periphery of the upper level ridge
building offshore, which will maintain nearly identical conditions
to Friday across western Washington through the weekend.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Conditions on Sunday and
Monday will bring more of the same under zonal flow as high
pressure continues to build offshore, with light surface onshore
flow and highs in the low to mid 80s.

A high pressure ridge situated offshore will sharply amplify
during the first half of next week, bringing much warmer
conditions and widespread Moderate (orange) HeatRisk to western
Washington on Tuesday and Wednesday. By Tuesday, the offshore
ridge will sharply amplify and a thermally induced surface trough
is on track to develop along the Pacific Northwest coastline.
Highs will reach the 90s on Tuesday for areas south of the Puget
Sound and along some Cascade Foothill and Valley locations.
Temperatures will continue to increase into Wednesday as the high
pressure offshore continues to build and the thermal trough
shifts northward, with areas across the Puget Sound lowlands on
track to reach the mid 90s. A few daily temperature records may be
broken towards the middle of next week, and a shift to easterly
winds through the Cascade gaps will likely bring elevated fire
weather concerns to the region.

15
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.AVIATION...
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A weak trough will swing ab occluded front across
western WA this morning. The flow aloft will turn more northwesterly
today with this trough. Radar is tracking showers moving through
areas north of Seattle, which are tracking eastward. A smaller band
of showers is tracking inland along the coast. These will be hit and
miss around the terminals (given the scattered nature). A
convergence zone does not appear likely at this time.

Conditions currently are a mix of VFR/MVFR/IFR. Satellite and
cameras are picking up on stratus development inland this morning,
which is expected to expand to cover all interior terminals this
morning (roughly by 12Z) with MVFR decks (expectation is 2,000-3,000
ft bases). A few spots from KPAE to KBLI may see CIGs drop below
2,000 ft (even 1,000 ft). Cascades will see low stratus this morning
down to IFR/LIFR, as well as the coast. Mist may drop visibilities
at coastal terminals down to 2 SM. Once the trough clears this
afternoon, a transient ridge will clear up most ceilings (interiors
will see improvement to VFR as early as 21Z, with scattering taking
place this evening. Another push will be possible Friday morning
with lower ceilings as the onshore flow translates down to the
surface.

Southwest winds this morning remain gusty in a couple spots (up at
KBLI gusting to 20 kt, elsewhere still 5-10 kt). These winds will
decrease through the day, and turn northwesterly late this afternoon
and evening regionwide at 4 to 8 kt.

KSEA...Few hit or miss showers possible at the terminal this
morning. Ceilings are expected to drop back down to MVFR early this
morning (only a 10% chance this is IFR), with VFR expected by
roughly 21Z. The chance for MVFR Friday morning is slightly lower,
but a marine push is expected to push stratus inland from the
southwest. Southwest winds 4-8 kt will decrease this morning, and
turn northwesterly by 22-00Z.

HPR
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.MARINE...
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An occluded front is currently sitting offshore over the
coastal waters, and will move inland this morning with a passing
upper level trough. Some scattered showers are ongoing with this
trough in some of the inland waters, and the coastal waters will see
some showers as well this morning. Additionally, areas of locally
dense fog will be possible again as the front passes through,
particularly later this morning. The coverage is not expected to be
widespread enough for a marine dense fog advisory, but may opt to do
a special weather statement later in the morning if fog does
develop. Visibilities down to a mile are possible, with isolated
areas seeing less than a mile.

Winds continue to decrease in the Strait of Juan de Fuca this
morning - will allow the small craft advisory to expire at 5 AM PST
this morning. The flow over the waters will turn northwesterly later
today post front. Diurnal pushes will continue through the strait
(but at this time do not appear they will reach small craft advisory
criteria). A trough passing to the north early next week may produce
gusty winds in the outer coastal waters, along with steeper seas.

Seas will range 3-4 feet today, increase to 4-6 feet Friday, and
further increase to 6 to 9 feet Sunday through Wednesday, Couple
spots further offshore may see 10 feet seas.

HPR
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.FIRE WEATHER...
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Cooler and more moist conditions will begin to cease
later today as skies clear and conditions being to warm up with a
weak upper level ridge building over the area. Friday will be the
warmest and driest day of the work week with RH values dropping
back into the 25% to 35% range over the mountains and across the
interior lowlands south of the Puget Sound. More robust onshore
flow will help usher in moist air this weekend despite high
temperatures remaining in the 80s.

While there is some model discrepancy, there is consensus that a
more robust upper level ridge will being to build and move into the
area by the middle of next week. Models are beginning show the
development of a thermal trough along the coast, which would allow
for winds to shift to offshore, promoting much drier and warmer
conditions as well as some potential breezy winds through the
Cascade gaps. This pattern will continue to be closely monitored as
we approach next week.

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.SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None.
PZ...Small Craft Advisory until 5 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.
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