402
FXUS66 KSEW 272200
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
300 PM PDT Mon May 27 2024

.SYNOPSIS...An upper level ridge will begin to build to the east
of the area today, while upper level troughing over the northeastern
Pacific continuing to influence western Washington. This will
bring warmer temperatures to the area today, but will allow for
some light showers to develop along the coast. The next frontal
system will then move across the region tonight into Tuesday,
bringing greater precipitation chances to the region through
Wednesday. Drier and warmer conditions will return at the end of
the work week into the weekend.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...An upper level ridge will
continue to build eastward of western Washington this afternoon,
while broad troughing offshore will continue to keep an influence
over western Washington. Temperatures will warm to around normal
this afternoon, into the upper 60s. Locations near the coast and
other bodies of water will have high temps stay in the mid to
upper 50s. Shower chances will start to increase this evening over
the coast and into Tuesday as an approaching frontal system and
trough nudges closer to western Washington.

The front will move across the region on Tuesday with rain
spreading through the interior by the afternoon and onshore flow
increasing. Latest hi- resolution guidance depicts a convergence
zone developing in the late afternoon and evening, especially in
and around the Snohomish/King county line. High temperatures on
Tuesday will cool back down to the upper 50s.

As the front exits the region on Wednesday, the aforementioned
troughs axis shift inland, keeping lingering showers in the
forecast across much of western Washington. Along with showers in
the area, cooler air aloft may promote instability that could lead
to a few convective showers over the interior and the Cascades
Wednesday afternoon. Lightning, small hail, gusty winds, and
brief heavy downpours will be possible in any thunderstorms that
do develop.

The upper level trough will move eastward on Thursday, allowing
for an upper level ridge to build in the Pacific. Conditions will
start to warm and dry out, with afternoon high temperatures
topping out in the mid 60s for the interior, and the upper 50s for
coastal locations.

.LONG TERM /FRIDAY THROUGH MONDAY/...Ensemble and deterministic
guidance supports drier and warmer conditions into the weekend,
as an upper level ridge takes shape over western Washington.
Temperatures look to warm into the upper 60s to low 70s by
Saturday. The ridge axis looks to push inland on Saturday, which
could open the door for additional systems to move through western
Washington by late Saturday into early Sunday. While
discrepancies in the ensemble data remain in regards to the
location of the ridge and trough axis in the later half of the
weekend, unsettled weather will look to return.

Mazurkiewicz

&&

.AVIATION...VFR conditions this evening with weak high pressure
over the region. The flow aloft is SW. Moisture will increase on
Tuesday as an upper trough drags through western WA. Expect rain
and possible IFR conditions along the coast by 12z. Rain will
spread into the interior by 15-18z with MVFR conditions. Showers
with a convergence zone likely over the King/Snohomish line
Tuesday night in post-frontal onshore flow. 33

KSEA...VFR tonight with W winds veering to N around 5-8kt. Winds
becoming S again by 12z. Rain and possible MVFR conditions around
18z Tue. 33

&&

.MARINE...Weak high pressure will shift inland tonight. A frontal
system will cross western WA on Tuesday with increasing onshore
flow Tuesday night (Small Craft Advisory winds likely through the
Strait of Juan de Fuca). Strong high pressure over the NE Pacific
will maintain onshore flow through the end of the week. 33

&&

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

$$