894
FXUS66 KSEW 152139
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
239 PM PDT Sat Jun 15 2024

.SYNOPSIS...Unsettled, cool conditions will persist over Western
Washington into Sunday as an upper level trough remains over the
region. The trough will shift east of the region on Monday and a
trend toward warmer and drier conditions will commence Tuesday
through the end of the week as higher pressure aloft gradually
rebuilds into the region.


&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Scattered showers and
isolated thunderstorms continue across Western Washington this
afternoon as an upper level trough axis remains in place over the
area. With the strong June sunshine, modest instability will
continue the thunder threat through sundown. In addition,
increasing onshore flow will provide some focus for a convergence
zone around the Snohomish/King county line into late this evening.
Some of the precip rates could be locally heavy with the
convection and, for that reason, a flood watch remains in effect
for the Bolt Creek burn scar through this evening.

The upper trough axis gradually shifts southeastward during the
day on Sunday. The keeps a chance of showers in the forecast,
though the instability indices decrease with time. The trough axis
shifts east of the Cascades Sunday night into Monday with north to
northwest flow aloft developing. Drier conditions are expected on
Monday with residual showers mostly focused over the higher
terrain of the Cascades. Heights continue to rise on Tuesday, but
only modestly so with weak troughing aloft and low level onshore
flow still in place. Nonetheless, plentiful sunshine is slated to
return on Tuesday with temperatures bouncing back to near
seasonal norms.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Looking ahead to the
second half of the coming week, ensembles generally support the
return of flat to low amplitude upper ridging with 500 millibar
heights back into the 570s dam. With onshore flow continuing, some
of the guidance might be a little overzealous with some interior
locations getting into the 80s. Nonetheless, a return to seasonal
temperatures and generally dry conditions during the extended
period looks like a reasonable forecast at this time.  27

&&

.AVIATION...Broad upper level trough over the Pac NW with a cool
and slightly unstable air mass over western WA. Showers continue
across the region this afternoon and evening with a threat of
thunderstorms too, especially near the King/Snohomish county line
where there`s low level convergence. Shower and thunderstorm
activity starts to fade by 03-06z this evening. Onshore flow will
keep the low level air mass moist overnight with low clouds and
MVFR conditions by morning. Another round of showers on Sunday as
the cool upper low tracks overhead. 33

KSEA...Showers and possibly thunderstorms in the vicinity through
around 01z this afternoon/evening. Thereafter, the focus for
stronger convection will likely be north of the terminal in the
convergence zone. Gusty S/SW to 25 kt easing after 03z. Low clouds
and MVFR conditions possible by 12-15z Sunday. 33

&&

.MARINE...Onshore flow prevails tonight with highest wind and
waves through the Strait of Juan de Fuca - a Small Craft Advisory
remains in effect. High pressure over the NE Pacific will maintain
light to moderate onshore flow moving through next week. 33


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

&&

$$