920
FXUS66 KSEW 041129
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
329 AM PST Tue Nov 4 2025

.SYNOPSIS...
Weak system over the southeast portion of the area moving off
to the east this morning. Warm front moving up from the south
will spread rain over the area tonight. Trailing cold front will
stall over Western Washington Wednesday before dissipating
Wednesday night. A fast moving system will arrive Thursday for
another round of rain and windy conditions into Friday. Possible
break Saturday before a splitting system for Sunday night and
Monday.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...Satellite imagery and
doppler radar show weather system over the southeast portion of
the area kicking off to the east this morning. Could still see a
little rain over the Central and Southern Washington Cascades
early this morning. Very temporary upper level ridge building
over Western Washington later this morning ahead of a developing
system offshore. Low level moisture from the rains Monday into
Monday evening combined with the increasing middle and high
level moisture in the afternoon making for a mostly
cloudy/partly sunny day over the southern portion of the area.
More sunshine over the northern portions this morning before
increasing middle and high clouds this afternoon. Highs near
normal, mid and upper 50s.

Warm front moving into the area late tonight with rain spreading
over Western Washington from south to north this evening. Cross
cascade surface gradients going negative this afternoon will
becoming more negative this evening bottoming out around -10
millibars. Have issued a wind advisory for the foothill zones
for east to southeast winds as high as 30 mph with gusts as high
as 45 mph. This is a borderline advisory but with leaves still
on the trees there is a chance for some downed limbs and power
outages. Winds in the foothills easing early Wednesday morning.
Snow levels rising quickly tonight up to 6500 to as high as 8000
feet so the precipitation type in the passes will be in the form
of rain. In the middle of winter this would be a classic freezing
rain in the passes scenario. Lows tonight in the mid 40s to
lower 50s.

Warm front north of the area early Wednesday with the trailing
cold front arriving during the day. Still the same story with
the cold front, jet aimed at Northern California and parent low
well to the north. This combination will slow the eastward
movement of the front down stalling the front over Western
Washington Wednesday afternoon. Even with rain Western
Washington will be in the warm sector until the front arrives.
Good chance the warmest locations get into the lower 60s.

In addition to the rain Wednesday, tides will be high. Seas on
the coast increasing to 10 to 14 feet. This along with the
winds and lower pressure could create tide anomalies in the 2
to 3 foot range bringing up the potential for moderate and even
a chance of major coastal flooding along the Washington coast.
High tide along the coast will be late Wednesday morning. Tide
anomalies not as high inland so for now coastal flooding not
forecast for the inland waters.

Cold front dissipating over Western Washington Wednesday night.
Slight chance of thunderstorms west of Puget Sound in the post
frontal cooler air mass. The chance of thunderstorms will be
brief with the next system moving quickly across the eastern
Pacific, Lows mostly in the mid to upper 40s.

The beat goes on Thursday with yet another system making it way
into the Pacific Northwest. IVT values still around 500 kg/m/sec
with the arrival of the rainfall Thursday morning making this a
weak atmospheric river. IVT values drop below 500 kg/m/sec by
the end of the day. Unlike the previous systems where the jet
was aimed at Northern California this time the 100-120 knot jet
is aimed at Western Washington. Strong west southwesterly flow
at 850 mb along with elevated snow levels will create
significant rainfall amounts along the south slopes of the
Olympics. A flood watch for Mason county for possible Skokomish
river flooding has been issued ( see hydrology section for more
details ). With the jet over the area this system has the best
chance of producing wind advisory wind speeds along the coast
and over the Northwest Interior. Highs in the mid to upper 50s.
Felton

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...While the
operational model solutions show the front moving through
Western Washington Thursday night the ensembles are a little
slower with the frontal passage pushing it back into Friday.
Ensembles showing an even stronger signal for a dry Saturday
with an upper level ridge building over the area while the next
weather system develops well offshore. Blend has put in some 20
percent pops for the area Saturday. Ensembles solutions are
90-95 percent dry on both the GFS and ECMWF. If this trend
continues look for the slight chance pops to be taken out of the
forecast Saturday into at least the first half of Sunday. Wet
ensemble solutions increase after 00z Monday. Models bringing
another system into the area Sunday night into Monday. This
system showing the same characteristics as most of the systems
so far, deep trough digging behind the system. In addition the
models are now putting the jet stream parallel to the front.
This will help slow the system eastward movement. Still have
chance pops Sunday afternoon and likely pops Sunday night but
the chances are increasing that Western Washington could see a
dry weekend. What is left of the front moving through Monday.
Felton

&&

.AVIATION...
Westerly flow aloft will become southerly tonight as a strong warm
front approaches the area. Low level offshore flow will increase
with gusty easterlies near gaps in terrain late this afternoon and
evening. Areas of MVFR/IFR will lift to VFR this afternoon. Ceilings
gradually fall tonight as precip spreads inland with the next
system.

KSEA...MVFR expected through mid-morning as low level moisture
congeals with light surface winds. VFR this afternoon into the
evening. Next round of rain will arrive late this evening. Surface
wind will become E/NE and occasionally gusty after 00Z.   27

&&

.MARINE...
A strong frontal system will move into the offshore waters late this
afternoon. A warm front and associated triple point will lift
northward toward the outer coastal waters late tonight. A strong
east to southeast pressure gradient associated with a 970 millibar
surface low passing well offshore will lead to widespread gales
across the coastal waters and Strait of Juan de Fuca tonight into
Wednesday. This surface low will generate large surf that will reach
the coastal waters on Wednesday with seas rising to in excess of 15
feet. Hazardous surf will persist into late week as a series of
additional fronts produce more headlines for wind and seas across
area waters. 27

&&

.HYDROLOGY...
Predicted rainfall totals over the south slopes of the Olympics
from Wednesday night through Friday morning in the 2.5 to 4
inches range with locally higher amounts. The Skokomish river
will already be neat actions stage from the rain Tuesday night
and Wednesday. This additional rainfall has a good chance of
causing the river to go above flood stage as early as Thursday
afternoon. A flood watch has been issued for Mason county for
Thursday afternoon through Saturday morning.

Rainfall amounts in the Cascades forecast to be a little less,
in the 1.5 to 3 inch range. West southwesterly flow aloft will
focus some of the heavier rain in the Cascades of Northern King
and Snohomish county. No flooding is predicted at this time for
rivers flowing off the Cascades. The Snoqualmie, Skykomish and
Snohomish could get into action stage with the heavier rain in
the headwaters. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory from 6 PM this evening to 4 AM PST Wednesday for
     Foothills and Valleys of Central King County-Foothills
     and Valleys of Pierce and Southern King Counties-
     Foothills and Valleys of Snohomish and Northern King
     Counties.

     Flood Watch from Thursday afternoon through Saturday morning
     for Foothills of the Western and Southern Olympic
     Peninsula-Middle Chehalis River Valley-Olympia and
     Southern Puget Sound-Olympics-Southern Hood Canal-Willapa
     and Black Hills.

     Coastal Flood Watch from Wednesday morning through Thursday
     evening for Grays Harbor County Coast-Northern Washington
     Coast.

PZ...Small Craft Advisory from midnight tonight to 4 PM PST
     Wednesday for Grays Harbor Bar.

     Gale Warning from 2 PM this afternoon to 6 PM PST Wednesday
     for Central U.S. Waters Strait Of Juan De Fuca-West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 6 PM this evening to 4 PM PST Wednesday for
     East Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 10 PM this evening to 10 PM PST
     Wednesday for Admiralty Inlet-Northern Inland Waters
     Including The San Juan Islands.

     Gale Warning from 6 PM this evening to 6 PM PST Wednesday 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 from 6 AM this morning to 6 PM PST this
     evening 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.

&&

$$