411
FXUS66 KSEW 161605
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
905 AM PDT Sun Jun 16 2024

.SYNOPSIS...Showers and isolated thunderstorms will continue today
as an upper level trough remains over the region. The trough will
shift east on Monday with lingering showers over higher terrain. A
warming and drying trend will commence for the remainder of the
week as high pressure aloft gradually builds into the region.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Upper trough remains over
the region, but instability will be somewhat less today as
temperatures gradually warm aloft. Flow at the surface and aloft is
weak, so showers that do form today will be slow movers. Current
forecast looks on track.  27

As of 2 AM PDT, convergence zone showers between Snohomish and
Stevens Pass are slowly tapering off. Rain rates have lessened with
these showers, and the Flash Flood Watch for the Bolt Creek burn
scar has been allowed to expire. Alongside the convergence zone
activity, light showers along the coast will continue to progress
inland with onshore flow while showers just north of the Canada
border continue to shift southward with an advancing front.

An upper level trough will slowly drop southward throughout the
day today, swinging a frontal system across western Washington.
Another round of showers will spread southward throughout the day
with embedded thunderstorm activity mainly southwest of the Puget
Sound, where models show instability peaking around 250-300 J/kg
in the early afternoon. Storms that develop may produce small
hail, locally heavy rain, and gusty outflow winds alongside
lightning. The primary push of moisture will taper off by this
evening, with another round of showers mainly over higher terrain
moving southward across western Washington early Monday morning as
a disturbance in the northerly flow aloft ripples through.
Conditions will dry out for most areas on Monday, except for
light showers favored to linger over the North Cascades. Another
shortwave trough will drop across the Pacific Northwest early
Tuesday, stirring up more light shower activity once again
favored over the mountains. Temperatures will remain on the cool
side in the mid 60s today and Monday before returning to near-
normal around 70 degrees by Tuesday.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Ensembles continue to
highlight weak flow through the extended period with a warming
trend through at least mid-week. Onshore flow will keep coastal
areas cool while lowlands further inland are on track to reach 80
degrees by Thursday. Temperatures will slowly moderate thereafter
with mostly dry conditions through the period.

Lindeman

&&

.AVIATION...A broad upper level trough remains over the Pac NW with
a cool and slightly unstable air mass over western WA - with
additional showers expected. Ceilings are a mixed bag with pockets
of MVFR conditions. The trend is for most areas seeing VFR
conditions this afternoon. As the upper level low continues to move
south and east throughout the day, flow aloft will be variable for
much of the day before turning to the northeast by tonight and
becoming more northerly Monday. 33

KSEA...MVFR conditions in place this morning and will likely stay
that way til around 18Z. Still a little instability expected this
afternoon, which will give cigs a boost but will also carry shower
chances. PoPs remain low and does not look to be enough instability
to warrant any thunder mention in the forecast. Surface wind
discussion immediately above this section applies.

33/18

&&

.MARINE...High pressure over the NE Pacific will maintain light to
moderate onshore flow across western WA this week. Expect a westerly
surge through the Strait of Juan de Fuca this evening - a Small
Craft Advisory is in effect.

Seas generally 4 to 6 feet for much of today before increasing to 6
to 8 feet tonight. These will ease throughout the day Monday,
getting back to 4 to 6 feet by Monday evening.

33/18

&&

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

$$