413
FXUS66 KSEW 171008
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
308 AM PDT Thu Jul 17 2025

.SYNOPSIS...Western Washington is poised for a pattern shift,
ushering in cooler temperatures along with night and morning
clouds. An upper level low will bring a chance of showers over
the Cascades Monday and Tuesday.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...The transition to cooler
conditions begins today. The marine layer will spread partially
inland this morning before burning back toward the coast.
On Friday, a weak upper level trough is expected to swing through
the region, further reinforcing the cooling trend. The weekend
will start with continued cool and mostly cloudy conditions with
some partial clearing Saturday afternoon.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Sunday will see a similar
pattern of morning clouds followed by some afternoon sun. Persistent
onshore flow will keep temperatures a little below average for
this time of year. An upper trough on Monday will lead to a mix of
clouds and sun with a chance of showers over the Cascades. A
warming trend may begin to take shape by the middle of next week
as the upper level low shifts eastward and a ridge builds
offshore.

&&

.AVIATION...Upper level ridge well offshore with northwesterly
flow aloft. Upper level trough moving by to the north Friday with
the low aloft turning westerly. In the lower levels onshore flow
continuing through Friday.

IFR stratus along the coast getting as far east and the southern
portion of the Hood Canal by 14z. Stratus retreating back off the
coastline by 21z. Clear skies for the remainder of the area.

KSEA...Clear skies through early Friday morning. Stratus
approaching the terminal after 12z Friday. Southwest wind 4 to 6
knots becoming westerly ( 250-280 degrees ) around 19z,
northwesterly 4 to 8 knots around 23z and then back to
southwesterly around 06z tonight. Felton

&&

.MARINE...Higher pressure over the coastal waters with lower
pressure inland will result in varying degrees of onshore flow
into the first part of next week.

Small craft advisory westerly winds in the Central and Eastern
Strait tonight and Friday night with possible evening small craft
advisory westerlies over the weekend.

Choppy seas in the outer coastal waters through Friday and over
the inner coastal waters today with seas around 8 feet and periods
around 9 seconds. Felton

&&

.FIRE WEATHER...The initial marine push will be shallow, so RHs
will be slow to recover again today. Elevated fire conditions
will continue today with another warm and dry day expected across
the area. A significant cooling trend will commence on Friday
with a return of cooler and more humid conditions through early
next week.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 5 PM PDT this afternoon for City of Seattle-
     Downtown Everett / Marysville Area-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 the North Cascades-Lowlands of Pierce and Southern King
     Counties-Lowlands of Western Skagit and Northwestern
     Snohomish Counties-Lowlands of Western Whatcom County-
     Shoreline / Lynnwood / South Everett Area.

PZ...Small Craft Advisory until 5 AM PDT early this morning 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.

&&

$$