654
FXUS66 KSEW 301617
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
917 AM PDT Tue Sep 30 2025

.SYNOPSIS...A frontal system will move through the area this
afternoon into Wednesday, bringing widespread rain, breezy to
gusty winds, and a slight chance of thunder across the area.
Unsettled conditions are favored to continue late into the week as
additional systems move into the region. Drier conditions may
return for the weekend.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...The precip shield ahead of
the next frontal system is approaching the outer coastal waters this
morning. This is still on track to reach the coast early this
afternoon then spread into interior areas toward early evening. QPF
values are largely unchanged from previous forecasts with the bulk
of the precip falling over the Olympic Peninsula over the next 72
hours with considerably lighter amounts around Puget Sound. For most
areas, the most impactful result of this system will be breezy to
locally windy conditions through tomorrow as a vertically stacked
trough wobbles offshore and gradually loses its intensity. Current
forecasts look good with no updates anticipated this morning.
Previous discussion follows with updates to aviation portion. 27

Latest radar imagery shows few post-frontal showers weakening across
the area. A brief reprieve from rain this morning will end fairly
quickly as a frontal system approaches the coast. A front will move
onshore this morning, with rain starting to push through the coast
by midday, spreading into Puget Sound and the rest of the interior
by the early evening hours. As the front moves across the region
this afternoon, breezy to gusty winds will be noticeable throughout
the interior, especially for areas along the coast and the North
Interior. A Wind Advisory continues to be in in effect for the
coastal areas, along with San Juan County, where wind gusts of 45
mph can be expected. Elsewhere, gusts of 25 mph will be likely
throughout the rest of the interior, with wind gusts likely peaking
this evening. Additionally, latest model runs have continued to
suggest a 20-30% chance of thunder this evening, primarily along the
coast with a lower chance (5-10%) within the interior.

The aforementioned frontal system will continue pushing through
the area Wednesday into Thursday with widespread rain and locally
breezy to gusty winds (with the highest wind gusts mainly along
the coast and in the North Interior). Thunder chances will
increase over the Olympics and the interior Wednesday evening,
with a 30-40% chance of an isolated thunderstorm or two along the
coast and Olympics, and a 15-20% chance over much of the interior.
QPF totals over the Olympic Peninsula by Thursday could range
from 4 to 7 inches, being the first significant rainfall of the
season. Areas in the Cascades will likely see a 1-2 inches, with
0.25 to 1 inch ranging through interior locations. Wave heights
along the coast will approach 15 feet or higher on Wednesday. This
could generate hazardous surf conditions with waves running
higher on beaches that can sweep people off jetties and
breakwaters - with a High Surf Advisory in effect. Beach erosion
is also possible.

Conditions will remain unsettled on Thursday with rain slowly
tapering throughout the day. Temperatures will remain near normal,
in the mid 60s.

.LONG TERM /FRIDAY THROUGH MONDAY/...Ensembles continue to point
to a drying trend heading into the weekend and into early next
week as a weak ridge attempts to build offshore. Uncertainty still
does exist on when this ridge builds - as a couple of systems
brush by western Washington that could continue to give us low-end
shower chances throughout the weekend. As for now, will leave
chance of showers in the forecast but with minimal QPF as
confidence nudges towards drier conditions.

28

&&

.AVIATION...Southwest flow aloft will persist through the TAF
period as upper level low approaches the region offshore. Lingering
shower activity across which should continue to taper over the next
few hours ahead of the next system. Similarly ceilings and
visibilities across area terminals should also improve. Low fog that
has developed this morning should lift with conditions improving
back towards VFR by the late morning hours. Another frontal system
approaching the coast will bring another round of rain to the coast
between 18-21Z and the interior between 21-00Z. Southerly winds will
increase areawide today, starting along the coast this morning and
increasing across the interior through the afternoon hours. Gusts to
25 kt will be possible areawide, but will be higher along the coast.

Isolated thunderstorms will also be possible through the day,
primarily for terminals along the coast. However, confidence is not
high enough to include in the TAF issuance at this time.

KSEA...VFR ceilings at the terminal through the evening, with rain
reaching the terminal during the lat afternoon/evening hours and
ceilings lowering to MVFR levels early Wednesday morning.   Light
winds through the early morning, with southerly winds expected to
pick up to 10-20 kt by this afternoon. Gusts to 25 kt will be
possible.
The next round of rain will likely approach the terminal between 21-
00Z.

14/Cook

&&

.MARINE...A strong frontal system will move across the area waters
today into Wednesday, bringing southerly gale force winds to the
Coastal Waters, Eastern Strait of Juan de Fuca, and portions of
the Northern Inland Waters. Elsewhere, small craft strength winds
are expected with the exception of the Central Strait, which
should largely remain sheltered to southeasterly winds. Winds
will start to increase over the next few hours and will remain
elevated into Wednesday as a strong low pressure system churns
offshore. Seas currently hovering between 6-9 ft will rapidly
build towards 15-17 ft today and to 16-19 ft by Wednesday.

The low pressure system offshore will then weaken on Thursday and
push inland on Friday, allowing for winds to decrease across the
area waters. Seas will gradually subside to below 10 ft through
the day on Thursday and down to 5-7 ft by Friday. Additional weak
systems may move through the area waters over the weekend, however
expect high pressure to build back over the northeastern Pacific
by the end of the week.

14

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 2 PM this afternoon to 11 PM PDT this evening
     for San Juan County.

     High Surf Advisory from 11 AM this morning to 5 AM PDT Thursday
     for Grays Harbor County Coast-Northern Washington Coast.

     Wind Advisory from 11 AM this morning to 8 PM PDT this evening
     for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory from 11 AM this morning to 5 AM PDT
     Wednesday for Grays Harbor Bar-Puget Sound and Hood Canal.

     Small Craft Advisory from 5 AM early this morning to 5 AM PDT
     Wednesday for Admiralty Inlet-West Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Gale Warning from 5 AM early this morning to 5 AM PDT Wednesday
     for East Entrance U.S. Waters Strait Of Juan De Fuca-
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 2 AM PDT early this morning 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.

     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.

&&

$$