000
FXUS66 KSEW 262203
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
303 PM PDT Sun Sep 26 2021

.SYNOPSIS...A series of fronts will move through the area tonight
for breezy winds and rain. A more showery pattern Monday and
Tuesday with isolated thunderstorms. Another system will move
through Wednesday night and Thursday for additional rain and
winds. Drier weather over the weekend.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...A system located
offshore of the coast will move across the area tonight. Rain
is spreading across much of the coast and into the interior this
afternoon, with rain into tonight. The upper low located offshore
will strengthen over the next few hours. Increasing southerly
winds with this system into this evening. Some uncertainty in
guidance as to the exact gusts for the area, but gusts of 40 to
50 MPH possible for the coast (especially immediate coastline),
with a Wind Advisory for these areas. Winds will be a bit less
for the interior, though gusts of 30 to 35 MPH are expected with a
few stronger gusts across western Whatcom/Skagit/San Juan Islands
areas into tonight. Winds may be strong enough to bring down tree
limbs with leafs on the trees along with isolated power outages.
Winds will be breezy into Monday with onshore flow.

A trough will be over the area Monday and Tuesday for more
convective showers. A few isolated thunderstorms are possible,
especially Monday afternoon. The thunderstorm threat will be more
limited on Tuesday, potentially focused in the area of a
convergence zone that may develop across the central Puget Sound
area. Breezy winds through Tuesday. Cooler weather Monday and
Tuesday with highs in the upper 50s to 60s. A possible brief dry
period early on Wednesday for the interior with another front
moving onshore Wednesday into Wednesday night for rain and winds,
especially for the more northern areas. Temperatures in the 60s.

.LONG TERM /THURSDAY THROUGH SUNDAY/...A front will move across
the area Thursday for rain and breezy winds. Ensembles suggest
the strongest winds will be along the coast and northern areas.
The front will weaken over the area early Friday as some ridging
builds in late Friday. The ridge will be over the area over the
weekend for mainly dry weather, although a front may near the
area on Sunday for a slight chance of precipitation along the
coast, as highlighted in some ensemble guidance. Cooler
temperatures Thursday and Friday with the late week front with
some warming Saturday and Sunday with the building ridge. JD

&&

.AVIATION...Increasing clouds and rain showers are moving into
Puget Sound this afternoon ahead of the next frontal
system.Conditions are largely MVFR across western Washington, with
some areas dipping into IFR. Further deterioration will be possible
through the evening and overnight hours as rain and breezy
conditions continue. Surface flow along the coast will be windy
through the evening hours, with southerly gusts up to 35-45 knots.
Throughout Puget Sound, breezy conditions are expected, with gusts
generally ranging from 20-30 knots. The airmass will become more
unstable into Monday in the wake of the frontal passage, allowing
for a slight chance of isolated thunderstorms across the area. Any
storms that develop tomorrow have the potential to contain
lightning, erratic winds up to 35 knots, and heavy rain.

KSEA...Rain has made it to the terminal this afternoon and will
likely continue through the current TAF period. MVFR conditions with
surface visibility between 4-6 miles will persist until around 15Z
Monday where a reduction to IFR is possible. Breezy southerly flow
will continue through the period, generally between 9-15 knots
sustained. The airmass will be unstable in the wake of the frontal
passage on Monday, and thunderstorms are possible but confidence was
low enough to exclude from the TAF at this point in time.

Kristell

&&

.MARINE...A much more active weather pattern taking shape across the
waters this week. A leading front will arrive onshore early this
afternoon before pushing through late tonight and into early Monday.
Latest guidance has trended slightly stronger, and confidence has
increased that gales will develop ahead of the front over the
coastal waters with winds to 35 kt. Current small craft advisories
for the other zones remain on track. A second front trails behind on
Monday for another round of advisory strength winds across portions
of the waters. More significantly, a much larger west swell will
arrive, leading to combined seas building to around 15 ft. At this
time, confidence was not high enough to definitively say that 15-16
ft waves will impact the coast for a high surf advisory, but
conditions will remain hazardous along beaches and coastal fronts
nonetheless. Expect a similar situation toward midweek, with the
next strong front reaching the waters late Wednesday and pushing
onshore through early Thursday. Expect widespread advisory strength
winds and possible gales, along with larger seas again following the
front.

Kristell

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory until 10 PM PDT this evening for Central Coast-
     North Coast.

PZ...Small Craft Advisory from 11 PM this evening to 8 AM PDT Monday
     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-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning until 11 PM PDT this evening 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.

     Small Craft Advisory until 6 AM PDT Monday for Admiralty Inlet-
     East Entrance U.S. Waters Strait Of Juan De Fuca-Northern
     Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 6 PM PDT this evening for Puget Sound
     and Hood Canal.

&&

$$

www.weather.gov/seattle

NWS SEW Office Area Forecast Discussion