FXUS66 KSEW 182126
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
226 PM PDT Mon May 18 2026

.SYNOPSIS...
The weather pattern remains fairly steady with high pressure
situated offshore through the week with morning clouds and
afternoon sun. Temperatures will rise a bit each day through 
the end of the week before beginning to cool off this weekend 
into early next week. 

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
North/northwesterly flow prevails across western Washington
through the next several days, and with surface high pressure
dominating offshore, the pattern remains pretty steady. Plenty 
of sunshine for most this afternoon with some mountain cumulus 
and a dissipating front approaching the coast. High temperatures
this afternoon on track to reach the mid to upper 60s. This 
front will, however, be enough to bring a stronger onshore push 
tonight which will bring more widespread low stratus and some 
drizzly conditions across the area for Tuesday morning. Lows in 
the low to mid 40s. Clouds should slowly lift through the day 
but expect most of the day to be cloudy. Highs a little cooler, 
in the low to mid 60s.

The upper level ridge offshore will begin to amplify and tilt
onshore towards WA and BC, which will allow for a warming and
sunnier trend to begin. With clouds expected to clear out early
Wednesday morning, expect temperatures to be warmer, with highs
reaching the upper 60s to low 70s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The warming trend will continue through the end of the week,
with the warmest temperatures across the region expected
Thursday and Friday as the ridge traverses the area and more
robust onshore flow begins to move in Friday into the weekend.
Temperatures will top out Thursday and Friday into the low to
mid 70s, with upper 70s to near 80 possible in the southwest
interior and Cascade valleys.

The ridge deamplifies as it moves eastward and shortwaves begin
to move through it. This should help to not just start to cool 
temperatures, but also bring in clouds and chances for showers. 
Currently the best chances for showers will be Sunday night into
Monday, but there is still considerable uncertainty given the 
trough's evolution/placement, or if the ridge will win out and 
push the trough elsewhere.

62

&&

.AVIATION...
North to northwesterly flow aloft as upper level ridging remains
over the region with onshore flow in the low levels continuing.
All terminals seeing VFR this afternoon with some mid to high
level clouds around. Light and variable winds will turn
northerly after 00z and remain around 5 to 10 knots throughout
the evening. Winds will switch to S/SW around 09z-12z and will
maintain the same speeds. A weak system combined with onshore
flow will have more widespread stratus develop early Tuesday
morning, with likely MVFR/IFR conditions across area terminals. 

KSEA...VFR conditions this afternoon with light and variable
winds turning northerly around 00z-03z. Speeds will increase
slightly, generally remaining around to 5 to 10 knots throughout
the evening. Winds will also turn S/SW around 11z-14z but
maintain the same speeds. VFR will continue before stratus 
moves in at the terminal, bringing conditions down to MVFR (50 
to 60% chance) through 19z-21z Tuesday. Conditions will rebound
to VFR later Tuesday afternoon.

Mazurkiewicz

&&

.MARINE...
Surface high pressure will remain over the northeastern Pacific
throughout much of the week, bringing north to northwesterly
winds over the coastal waters. A splitting weak system will
cross over the waters tonight into Tuesday, bringing an
increased period of onshore flow throughout the Strait of Juan
De Fuca. A small craft advisory is in effect through Tuesday
morning for increased westerlies. 

High pressure will rebuild midweek and continue throughout the
rest of the week, which will provide continuous periods of
onshore flow. Can expect in daily pushes down the Strait of Juan
De Fuca through the rest of the week, which would likely
generate small craft advisory winds. A weak system looks to
enter the area waters Thursday into Friday.

Coastal seas generally increasing to 6 to 8 feet through the
first half of this week, with seas increasing more to 8 to 10
feet late Thursday and into Friday. 

Mazurkiewicz 

&&

.HYDROLOGY...
The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated during 
this time as needed.

&&

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

&&

$$