198
FXUS66 KSEW 171623
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
923 AM PDT Tue Sep 17 2024

.SYNOPSIS...A upper level trough and associated front will push
through the region late Tuesday for some rain showers into
Wednesday. Drier conditions into Thursday before unsettled weather
likely returns to the area through the weekend.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Forecast remains on track
this morning with the approaching front spreading some rain into
Western Washington. Previous discussion follows with no updates
this morning.

The forecast leans toward cooler conditions through Wednesday
with troughing over the Pac NW. High temperatures will track in
the 60s or a few degrees cooler than average. Expect lows in the
40s and 50s. Rain moves into the coast this afternoon with a few
light showers reaching the interior as well. Look for drier
conditions this evening as this system pushes south. May see light
rain or drizzle in the central sound Wednesday morning where
there`s convergence. Weak ridging nudges inland on Thursday for
drier and slightly warmer weather. 33

.LONG TERM /FRIDAY THROUGH MONDAY/...Onshore flow prevails into
the weekend as the flow aloft turns zonal. This opens the door as
wetter Pacific systems roll in, with most of the ensemble members
showing measurable rain. Skies remain mostly cloudy throughout
with the onshore conditions and moist low level air mass. With
this, temperatures will continue to trend cooler than average.
There`s little overall change in the pattern moving into early
next week for more fall-like weather. 33

&&


.AVIATION...West to southwest flow aloft will become
east/northeasterly tonight as the offshore upper level trough shifts
southward. Widespread IFR and/or lower MVFR ceilings across the
lowlands of Western Washington this morning are expected to lift
into the afternoon but ceilings will linger likely in the 2500 to
3000 foot range. Areas of light rain are expected to develop midday
mainly west of Puget Sound.

KSEA...Marine layer with MVFR ceilings - 1000 to 1500 feet will lift
through he late morning into the early afternoon to 2000 to 2500
feet. Surface winds southerly rising to 7 to 10 knots by late
morning. 27/cook

&&


.MARINE...A weak surface low will shift southward over the offshore
waters today into tonight, but is not expected to produce any
headlines. Broad surface ridging centered well offshore rebounds
Thursday into Friday. Northwesterlies may approach small craft
advisory levels late this week across the outer coastal waters,
otherwise fairly tranquil conditions are expected into early
Saturday. Forecast confidence is low by early next week, but model
ensembles suggest about a 20 to 30 percent probability of small
advisory level winds for portions of the coastal waters with a
frontal system on Sunday.  27

&&

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

$$