Napavine, Washington Weather Forecast Discussion

083
FXUS66 KSEW 201628
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
928 AM PDT Sat Sep 20 2025
.SYNOPSIS...Mostly dry and mild conditions continue today
before a frontal system move through the area late tonight into
Sunday morning, bringing widespread rain, breezy winds, and
cooler temperatures. High pressure will return Monday for a
return to sunny skies and warmer conditions through at least the
first half of the week.
&&
.SHORT TERM /TODAY THROUGH MONDAY/...Skies remain mostly clear
across much of western Washington, though marine stratus is
developing along the coast and will push inland a little bit
tonight. The Puget Sound area and the metro should remain under
clear skies. Lows will be again be cool for this time of year,
in the low 40s to low 50s. Stratus should quickly retreat,
allowing the sun to warm us back up into upper 60s on the coast,
with low to mid 70s for the interior.
Smoke from fires on the Olympic Peninsula will continue to
degrade air quality through today, through this incoming system
tonight into tomorrow should help to clear some of it out and
improve air quality.
Clouds will start to increase in the evening as the frontal
system approaches the area. Rain will first reach the coast late
this evening, moving across the interior early Sunday morning. The
heaviest rain will be before sunrise but showers may stick around
into Sunday morning. Additionally, a convergence zone may keep
some showers going over the metro area and towards the passes into
Sunday afternoon. With the trough axis directly overhead by
Sunday afternoon, there may be just enough instability for a
lightning strike or two, but overall the probability is low
(10-15%). Through Sunday afternoon, 0.5-1" will be possible across
the mountains and the Pacific coast, with the interior receiving
around 0.25-0.5" with this system. Definitely not a fire season-
ender, but should bring a temporary reprieve for the active fires
in the area. As the rain moves through overnight, low temperatures
will be warmer, in the mid 50s, though Sunday`s high temperatures
will remain quite cool, in the mid to upper 60s. Decreasing
clouds Sunday night should allow lows to once again cool quite
effectively, in the 40s to near 50 in the metro. Areas of fog will
be expected Monday morning. Upper level ridging will quickly
build over the area behind the trough Monday morning, allowing for
a rapid return to mostly clear skies and more seasonable
temperatures, with highs a few degrees on either side of 70 on
Monday.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/... Upper level ridging looks
to remain in place into Tuesday and Wednesday, allowing for a
gradual warm-up, back into the mid to upper 70s. Lows remain in
the 50s. The ridge looks to flatten around mid-week, which may
allow systems to move through and reach the area by late week into
next weekend and bring temperatures back close to/slightly below
normal, however there is considerable uncertainty as to how
quickly that occurs and whether or not incoming waves are able to
sustain themselves to reach the Pacific Northwest. That being
said, ensembles keep the area dry through Friday.
62
&&
.AVIATION...Southwest flow aloft will increase over Western
Washington today as an upper level ridge shifts eastward a trough
and associated frontal system approach the region. Most terminals
are VFR this morning. Marine stratus and/or isolated shallow pockets
of fog have brought LIFR conditions to the coast, Strait of Juan de
Fuca, Kitsap Peninsula, and southwest interior. Improvement into VFR
is expected for the interior terminals once the fog dissipates.
Coastal terminals may improve to MVFR late this morning/early
afternoon. Reduced visibility in smoke and haze will continue to
affect areas downwind of the Bear Gulch Fire, especially south
portions of Puget Sound eastward. High and mid level clouds will
increase late this afternoon and tonight. MVFR ceilings in rain will
develop along the coast this evening and will spread to the interior
areas overnight.
KSEA...VFR at the terminal this morning and will prevail for the
rest of today. High level smoke and haze will persist across the
area through much of the day. High and mid level clouds ahead of an
approaching front will increase this afternoon and evening, with
ceilings lowering to MVFR in rain near or after 08Z tonight. Light
surface winds this morning will increase out of the S/SW to 7 to 10
knots this afternoon and evening. Winds will become gusty for a
period with and behind the front early Sunday morning.
27/29
&&
.MARINE...A weak surface ridge over the waters will give way to
a weak trough and associated frontal system tonight into early
Sunday. This will cause increased winds over area waters as the
front pushes through and behind the front. High pressure will
rebuild over the waters later Sunday into Monday. Another thermal
trough expanding northward along the Oregon coast early next week
will turn the flow more northerly or weakly offshore. Onshore flow
will resume around midweek as another frontal system moving into
British Columbia passes mostly north of the area.
27
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Air Quality Alert until midnight PDT tonight for Foothills and
     Valleys of Thurston and Lewis Counties-Foothills of the
     Western and Southern Olympic Peninsula-Lowlands of Lewis
     and Southern Thurston Counties-Middle Chehalis River
     Valley-Olympia and Southern Puget Sound-Olympics-Southern
     Hood Canal-Willapa and Black Hills.
PZ...Small Craft Advisory from 11 PM this evening to 1 PM PDT
     Sunday for Central U.S. Waters Strait Of Juan De Fuca-
     East Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 1 AM to 9 AM PDT Sunday for Puget
     Sound and Hood Canal.
Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
     Sunday for Coastal Waters From Cape Flattery To James
     Island 10 To 60 Nm-Coastal Waters From Cape Flattery To
     James Island Out 10 Nm-Coastal Waters From James Island
     To Point Grenville 10 To 60 Nm-Coastal Waters From James
     Island To Point Grenville Out 10 Nm-Coastal Waters From
     Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal
     Waters From Point Grenville To Cape Shoalwater Out 10 Nm.
&&
$$

NWS SEW Office Area Forecast Discussion