347
FXUS66 KSEW 240920
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
220 AM PDT Mon Jun 24 2024

.SYNOPSIS...An upper level ridge will rebuild into the region
today and Tuesday for warmer and drier conditions. Another upper
level trough will produce showers and cooler temperatures across
the area Wednesday and Thursday. A weak upper ridge returns late
in the week for a drying trend, but continued onshore flow will
keep temperatures near normal for the end of June.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Residual weak convergence
continues early this morning, but this will fizzle out later this
morning as onshore flow continues to weaken and the low level
flow turns more northerly. An upper trough centered over the
interior of British Columbia will continue to weaken today as it
gradually shifts eastward into Alberta. This will allow upper
ridging to rebuild into Western Washington today. With the
resulting subsidence and drier air mass, skies will clear out most
areas by this afternoon with high temperatures rebounding to
seasonal norms.

Heights continue rise into Tuesday as strong upper ridging
centered over the Desert Southwest builds into the Northern
Rockies. High temperatures across the interior of Western
Washington will warm several degrees with 70s common and few spots
across the Southwest Interior getting into the lower 80s. A
persistent sea breeze will cap temperatures mostly in the 60s
along the immediate coast. Upper ridging shifts eastward on
Wednesday as yet another upper trough moves into the region.
Models continue to generate some respectable QPF with this system.
Showers will spread onshore across the Olympic Peninsula Wednesday
morning then eventually to interior areas by Wednesday evening.
There may be enough instability with this system to generate a
thunderstorm or two near the crest of the North Cascades Wednesday
afternoon. High temperatures will cool 10 or more degrees across
the board.

.LONG TERM /THURSDAY THROUGH SUNDAY/...The upper trough axis
shifts onshore on Thursday giving nearly all of Western Washington
a shot at some measurable precipitation. Meso models are keying
in on a decent convergence zone setting up early Thursday morning.
The trough axis is expected to shift east of the Cascades by
Thursday afternoon. The return of some weak upper ridging is
expected to lead to a drying trend and somewhat warmer
temperatures heading into the end of the week. For Sunday and
beyond, ensembles generally agree that weak upper troughing just
offshore will ensure that onshore flow continues keeping
temperatures from getting much above seasonal normals as June
comes to a close. 27

&&

.AVIATION...Onshore flow prevails across western WA today. The
flow aloft is westerly. There is weak convergence with light
showers over the central and north sound this morning, along with
MVFR conditions. Low clouds will lift and scatter this afternoon
with VFR conditions expected. 33

KSEA...MVFR ceilings likely to fill in this morning with light S
winds. Clouds scattering for VFR this afternoon. Winds flipping
to light W/NW by 21z. 33

&&

.MARINE...High pressure over the NE Pacific will maintain onshore
flow through Tuesday. Weak frontal systems will push inland on
Wednesday and again over the weekend. Strongest wind and waves
will be through the Strait of Juan de Fuca through the period with
possible Small Craft Advisories. 33

&&

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

$$