354
FXUS66 KSEW 171700
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
1000 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...VFR conditions at the majority of the terminals this
morning. Latest satellite imagery shows the marine layer well
situated along the coast this morning, and even managed to push as
far east as the Kitsap Peninsula and southern interior (KOLM). The
marine layer is slowly starting to retreat this morning, so not
expecting it to make it make it fully into KSEA and KBFI.
Improvement into VFR is expected after 18z-20z. Clear skies for the
remainder of the day.

Generally SW winds this morning turning westerly this afternoon,
before becoming NW this evening.

KSEA...VFR conditions expected today, with clear skies expected
through early Friday morning. Stratus approaching the terminal after
12z Friday. SW wind this morning becoming westerly (250-280 degrees)
around 19z-20z. NW winds this evening around 5-8 kt around 23z-0z
and then back SW after 8z-9z. Felton/29

&&

.MARINE...Higher pressure over the coastal waters with lower
pressure inland will result in onshore flow for 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/29

&&

.FIRE WEATHER...This morning`s marine push was able to bring
good RH recoveries along the coast, and into parts of the the
interior. There remains elevated fire weather concerns today for
dry, hot and unstable air (particularly for the Cascades as min
RH`s are expected to drop to 25-40%). Increasing northwest
winds 5-10 mph today into Friday will bring more cool/moist air
into these areas. A few gusts to 20 mph are possible Friday
afternoon in portions of the south interior. A chance of
isolated thunderstorms in the north Cascades next Monday/Tuesday
may bring elevated fire weather concerns (due to lightning).

HPR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory until 8 PM PDT this evening 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 from 6 PM this evening to 5 AM PDT Friday
     for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$