565
FXUS66 KSEW 200925
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
225 AM PDT Fri Sep 20 2024

.SYNOPSIS...Mainly dry weather today and Saturday. Rain spreads
inland on Sunday for a chance of rain over the coast, north part
and mountains. High pressure brings warmer weather moving into
Tuesday. Rain returns by midweek with wet and cooler weather
toward next weekend.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...We`re under NW flow today
with a ridge over the NE Pacific and a trough over western Canada.
We may see isolated showers in the interior and Cascades today
but otherwise looking mainly dry. Temperatures will continue to
track cooler than average and in the 60s.

The next frontal system stalls over southern B.C. on Saturday,
leaving western WA dry and mild. The air mass over western WA is a
little warmer with temperatures closer to average. Rain spreads
into western WA on Sunday but mainly impacting the coast, north
part near the border, and north/central Cascades. Precipitation
from Seattle south is light (trace to a few hundredths if
anything). 33

.LONG TERM /MONDAY THROUGH THURSDAY/...Light showers linger on
Monday with warmer and drier weather on Tuesday with high
pressure. Temperatures on Tuesday reach the 70s with a few low 80s
possible. Wetter weather returns toward midweek as the ridge
shifts east and moist S/SW flow sets up over western WA. We`re
back to a troughing pattern moving toward the end of the week for
additional showers and cooler weather. 33

&&

.AVIATION...Northwest flow aloft continues today as a weak
upper ridge rebuilds into the region. Low level onshore flow will
become light northerly later today. The air mass remains somewhat
moist in the low levels with low MVFR in widespread stratus expected
through late morning before lifting and scattering out to VFR 19Z-
21Z. Patchy fog/stratus will reform late tonight.

KSEA...MVFR ceilings expected through 18Z then lifting and
scattering this afternoon and evening. Current probabilities for low
stratus reforming on Saturday morning are relatively low at less
than 20%. Surface winds light southerly this morning veering
west/northwest this afternoon then northerly 7 knots or less by
evening. 27

&&

.MARINE...Onshore flow will gradually relax today as a weak surface
low in the vicinity of Tofino dissipates and a surface ridge
offshore expands in the coastal waters. The ridge will remain in
place into Saturday, but weaken on Sunday as a frontal system moves
onshore over southern British Columbia. No headlines are anticipated
with this. Thermally induced low pressure expanding northward along
the Oregon coast Monday into Tuesday will turn the flow more
northerly or weakly offshore. Onshore flow resumes by the middle of
the coming week as a weakening frontal system approaches the area.
27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 5 PM PDT this afternoon for Coastal
     Waters From Cape Flattery To James Island 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville 10 To
     60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

&&

$$