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FXUS66 KSEW 170919
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
219 AM PDT Tue Jun 17 2025

.SYNOPSIS...Upper level troughing will remain the dominant
influence across the region through much of the next week. Weak
systems will bring increased cloudiness and chances of showers to
western Washington today and Wednesday. More notable chances of
precipitation are expected Friday into Saturday as an upper low
moves inland over the region. Warmer and drier conditions are
expected to return by early next week.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Upper level troughing will
continue to remain the dominant influence over the region over the
next few days as an upper level low spins across the northeastern
Pacific. At the surface, a weak frontal system will approach the
region today, bringing chances of showers mainly to the coast
throughout the day. This system will then move inland overnight
into Wednesday, bringing showers into the interior. Overall
rainfall amounts with this system look to remain rather light,
with most lowland locations likely only receiving a few hundredths
to a tenth of an inch of rain. The bulk of the moisture remains
focused in the mountains, where locally higher amounts up to a
quarter of an inch of rain will be possible. High temperatures
will be in the low to mid 70s across the interior today and in the
low 60s along the coast. Afternoon highs across the interior will
then cool a few degrees on Wednesday, topping out in the upper
60s to low 70s, while temperatures along the coast remain steady
in the low 60s.

A few post-frontal showers will linger into Thursday, but generally
expect Thursday to be a transitional, drier day across western
Washington as a whole. Afternoon high temperatures will be similar
to Wednesday, topping out in the upper 60s to low 70s across the
interior and low 60s along the coast.

.LONG TERM /FRIDAY THROUGH MONDAY/...The most notable precipitation
of the week will arrive Friday into Saturday as the upper level
low spinning across the northeastern Pacific sinks southward and
pushes inland over the region. This system will bring more
widespread rainfall to the lowlands, with most spots looking like
they will receive anywhere from a quarter to half an inch of
rain at this time. This cool system will allow for snow levels to
fall between 5000-6000 feet over the weekend, bringing the
potential for light snow accumulations to the tallest mountain
peaks. Those with plans for outdoor recreation in the mountains
over the weekend will want to make sure to monitor the forecast
for the latest information. High temperatures will trend below
normal as a result, generally in the upper 50s to mid 60s across
the majority of the area.

Conditions start to warm and dry out again by Sunday with showers
expected to gradually taper through the day and become more
confined to the mountains by the evening hours. Some lingering
shower activity may persist over the mountains on Monday, but
expect the area to be drier overall as the low moves out of the
region. High temperatures will warm a couple degrees each day,
topping out in the mid to upper 70s across the interior by Monday
afternoon and in the mid 60s along the coast.

14

&&

.AVIATION...Southwest flow aloft continues today as troughing
approaches Western Washington offshore. VFR conditions prevail
across most of the area this morning, with the exception being
around HQM where low clouds are beginning to develop with IFR to
MVFR cigs around 1000 ft. Clouds should fill in along the coast and
begin to creep northeastward towards OLM and through portions of the
South Sound. Currently the areas most likely to see stratus remain
from PWT and TIW westward, but still cannot rule out the possibility
of a few hours of stratus at the Seattle area terminals. For now,
will maintain the mention of stratus at these terminals and will
continue to monitor the trends this morning. Any stratus that
develops should quickly retreat and scatter after sunrise this
morning for VFR conditions through most of the TAF period. A weak
frontal system will approach the area early Wednesday morning and
widespread MVFR conditions are expected Wednesday morning. Light
winds this morning will pickup to be W/SW 5 to 10 kt through tonight.

KSEA...VFR conditions this morning. Stratus is expected to fill in
and approach from the west and could get close to the terminal. Will
continue to mention scattered stratus this morning but there remains
a 15% chance for CIGs to fill in. Will continue to monitor trends.
Otherwise, VFR conditions persist the rest of today and Wednesday
morning. More widespread stratus will move in Wednesday morning for
MVFR cigs after 09-12Z Wed. Winds will remain W to SW up to 10 kt
through the TAF period.

62

&&

.MARINE...Surface high pressure will weaken today as a weak front
approaches the area. The front will moves through the area waters
Tuesday night into Wednesday. High pressure will briefly rebuild
Wednesday and Thursday before a low pressure system slowly moves
southward from BC Friday into Saturday. The overall pattern remains
benign with no significant winds, expect in the Strait of Juan de
Fuca, where diurnally driven pushes will continue each evening. The
next strongest looks to be Wednesday night into Thursday which could
require an additional advisory.

Seas remain 4 to 6 ft through Friday, bumping up to 6 to 8 ft early
Saturday with the system moving through before going back to 4 to 6
ft next week.

62

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$