Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
000
FXUS66 KSEW 211733
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
1033 AM PDT Thu Mar 21 2024

.UPDATE...Satellite imagery shows upper level low well offshore
with the coldest cloud tops also well offshore. Mostly cloudy
skies over Western Washington with some bigger breaks in the cloud
cover near the southern Puget Sound. Doppler radar has a few
showers over the Southwest Interior but most of the area is dry at
17z.

Forecasts on track this morning with just a chance of showers
this afternoon with the low spinning around offshore. Low drifting
east tonight increasing the chances for showers over the area.
Highest pops Friday night as the weakening front associated with
the low moves inland. No forecast update this morning. Updated
aviation section below. Felton

&&

.PREV DISCUSSION... /issued 316 AM PDT Thu Mar 21 2024/

.SYNOPSIS...An approaching trough of low pressure will produce
wet and unsettled conditions into the weekend. Additional fronts
will keep lowland rain and mountain snow in the forecast into next
week.

.SHORT TERM /TODAY THROUGH SATURDAY/...The first of several upper
disturbances ejecting from the broad upper trough offshore moved
across Western Washington overnight with scattered showers. Shower
activity will diminish later this morning and we`ll see a relative
lull in activity later today into early tonight. The offshore
trough begins to lift northeastward on Friday pushing a slow
moving front toward the coastal waters. This will lead to a
gradual increase in precip coverage across Western Washington
through the day on Friday. Periods of showers will continue into
Saturday as a series of disturbances rotate across the area around
an upper level low. The low finally is expected to shift onshore
over southern Oregon or northern California Saturday night.

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Somewhat drier north to
northwest flow aloft develops on Sunday ahead of weak shortwave
ridging. This should give the area a brief break from wet weather
later Sunday and perhaps early Monday before the first of several
seasonal frontal systems spreads additional lowland rain and
mountain snow across Western Washington. Temperatures through the
extended forecast period look to average a smidge below seasonal
norms. 27

&&

.AVIATION...Transient shortwave overhead with mostly southwest flow
aloft. A mix of VFR to IFR out currently with the trend expected to
last throughout the morning. Can`t rule out instances of LIFR also
(in and around KOLM). Some improvement is possible after 18-19z
today to mostly VFR over area terminals, although cannot rule out
observations of MVFR under passing showers. A mix of VFR and MVFR
will again be possible Thursday night into Friday morning.

KSEA...VFR/MVFR so far this morning as clouds keep breaking apart
and filling back in. However, mostly VFR is slated to return as
the day progresses and will continue overnight. Winds generally
out of the south between 5 to 10 knots, turning more SW during
the afternoon before becoming light overnight.

McMillian/Maz

&&

.MARINE...A weak frontal system is well beyond the offshore
waters of Oregon currently but no impacts are expected here locally.
An additional disturbance is on tap to arrive over the weekend but
at this time, conditions are to remain sub-SCA. Brief high pressure
to start the beginning of next week but the pattern will remain
generally active through the middle of it. Seas 3 to 6 feet
through much of the upcoming week before possibly rising next week.

McMillian

.HYDROLOGY...No river flooding is expected over the next 7 days.

&&

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

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.