029
FXUS66 KSEW 231653
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
853 AM PST Sun Feb 23 2025

.SYNOPSIS...An atmospheric river pattern will maintain wet
conditions across western Washington into early next week, with
periods of moderate to heavy rain and breezy winds. Conditions are
favored to dry out towards mid-week as high pressure develops,
with potential for more widespread precipitation next weekend.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...A brief break in the action
this morning with more rain headed our way this afternoon and
evening. S/SW winds also a little gusty this afternoon at 30-40
mph. Meanwhile, still watching the river levels although only
looking at an additional 0.5-1.50" in the mountains today/tonight
which is not too impressive overall (in terms of additional
flooding). 33

Previous discussion...An initial wave of precipitation from an
atmospheric river will continue to shift inland this morning as a
front crosses the Pacific Northwest, with 24 hour rainfall totals
reaching 3 to 4 inches over parts of the southern Olympics and
central Cascades. Much of the lowlands will dry out by the mid
morning, seeing brief relief from wet conditions into the early
afternoon with showers favored to linger over the Cascades. Snow
levels as high as 6000 ft over the mountains has allowed for sharp
rises to area rivers, with another injection of precipitation
later today keeping river flows high through the weekend.

The next round of moderate to heavy precipitation will spread
across western Washington this afternoon as another frontal
system lifts across the region. Breezy southerly winds will pick
up as the front moves through with gusts reaching 30 to 45 mph. A
few lightning strikes also cannot be ruled out in stronger showers
that develop. Conditions will dry out for most areas by the late
evening, with showers favored to linger over the mountains
overnight. The lowlands will see up to half an inch of additional
rainfall through the remainder of the weekend, with 1 to 2 inches
of rain over the mountains. Temperatures will stay on the mild
side, with highs today in the low to mid 50s.

After a brief break Monday morning, a deepening low offshore will
spread another round of moderate to heavy precipitation and gusty
winds across western Washington Monday afternoon to Tuesday. The
low will intensify as it approaches the Pacific Northwest coast on
Monday before stalling and weakening as it moves onshore. While
forecast models still show some variability over the exact track
of the low, confidence is high that strong winds will develop and
a High Wind Watch has been issued for areas along the Pacific
Coast. The convective nature of this system will also allow for
heavy showers to develop, with enough instability for isolated
thunderstorms Monday afternoon. This system will bring an
additional 1 to 3 inches of liquid for most areas between Monday
and Tuesday and up to 4 to 5 inches for higher terrain over the
Olympics and Cascades. With snow levels lowering to 3500-4000 ft,
the mountains will see accumulating snowfall over higher
elevations through Tuesday with several inches on track for the
higher Cascade Passes.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Forecast models continue
to favor a ridge building over the western US towards the second
half of the week, allowing for drier conditions. Temperatures will
stay on the mild side through Friday with highs in the 50s to
near 60 degrees across the lowlands. Chances for precipitation
increase by next weekend as ensembles highlight the return of
troughing over the Pacific Northwest.

15

&&

.AVIATION...Current radar imagery shows mostly dry conditions this
morning across western Washington. Ceilings are a mixed bag this
morning, with VFR conditions to the north and IFR to LIFR conditions
to the south in fog. Ceilings and visibility will likely bounce
around this morning, but generally expecting MVFR to IFR conditions
to spread over the area late this morning into this afternoon as the
next round of rain moves through this evening. Rain may be heavy at
times, limiting visibility. Models are hinting at conditions
returning to VFR for a brief period early tomorrow morning, and with
decreasing winds, this could permit fog development again with the
moist low levels.

South to southwesterly winds will pick up again this afternoon,
reaching 10 to 20 kt with gusts 25 to 35 kt by this evening. The
strongest winds will be along the coastal terminals. Winds will ease
overnight becoming light tomorrow morning.

KSEA...Conditions are bouncing around early this morning, with a
broken low level cloud deck and temporary reductions in vis in mist.
Expect conditions today to largely remain MVFR to IFR as the next
round of rain moves across the terminal this evening. Rain may be
heavy at times, causing reductions in vis. Guidance is hinting a
period of VFR conditions overnight, which may allow fog to develop
early Monday morning (20-25% probability). Rain will return to the
terminal late Monday morning as the next system approaches.

Light winds this morning will become south to southwesterly, peaking
this evening at 10 to 15 kt with gusts 20 to 30 kt. Winds will
slowly decrease overnight becoming light by Monday morning.

62

&&

.MARINE...Unsettled marine conditions are expected to persist into
Monday and early Tuesday morning. Winds will increase Sunday
afternoon into Sunday night into small craft criteria. A stronger
low pressure system will move across the waters Monday night into
Tuesday. High-end gale force winds with gusts approaching storm
force are possible along the central and south coastal waters, and a
Storm Watch has been issued. Winds will also increase in the
interior waters and may approach gale force criteria, prompting a
Gale Watch to be issued. Winds will begin to decrease on Tuesday
morning and more benign conditions will ensue across the waters as
high pressure develops Tuesday night. Models have high pressure
persisting through late in the week.

Combined seas of 8-11 ft on Sunday, and will build rapidly on Monday
night into early Tuesday morning. Waves in the coastal waters will
build to 20-30 ft, with the largest waves localized to the southern
coastal waters. Waves will begin to subside throughout the day on
Tuesday in Wednesday, but will remain between 10-12 ft through late
in the week.

29

&&

.HYDROLOGY...Rainfall amounts over the last 24 hours across the
western and southern slopes of the Olympics have ranged from 2 to 4
inches, with 1 to 4 inches recorded across the Cascades. These
amounts, combined with snow levels ranging 6000 to 8000 feet has led
to rises on area rivers across Western Washington. The Skokomish
River in Mason County has crested at moderate flood stage at around
17.5 feet and will remain above minor flood stage through mid week.
Continue to monitor the potential for additional rivers to rise
(Snoqualmie and Snohomish Rivers), but some rivers have crested and
have started to slowly fall. Lighter precipitation this afternoon is
not expected to cause additional rises from precipitation that fell
overnight. However, additional precipitation is expected at times
through Monday night, allowing for periods of additional rises on
area rivers. For that reason, the Flood Watch continues over the
next few days for most of Western Washington due to the continued
threat of river flooding. A hydrologic outlook also remains for
Jefferson, Clallam, and Whatcom Counties for a lower chance of
flooding. Landslide danger may also increase in some areas early
this week.

JD/HPR

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Flood Watch through late Tuesday night for Bellevue and Vicinity-
     Central Coast-East Puget Sound Lowlands-Everett and
     Vicinity-Lower Chehalis Valley Area-Olympics-Seattle and
     Vicinity-Southwest Interior-Tacoma Area-West Slopes North
     Cascades and Passes-West Slopes North Central Cascades and
     Passes-West Slopes South Central Cascades and Passes-
     Western Skagit County.

     High Wind Watch from Monday afternoon through late Monday night
     for Central Coast-North Coast.

PZ...Small Craft Advisory until 10 AM PST 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-Grays Harbor Bar-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Watch from Monday morning through late Monday night for
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From Cape Flattery To James Island Out 10
     Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Watch from Monday afternoon through Tuesday morning for
     Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De
     Fuca-Northern Inland Waters Including The San Juan Islands-
     Puget Sound and Hood Canal.

     Storm Watch from Monday morning through late Monday night for
     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.

&&

$$