719
FXUS66 KSEW 082313
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
313 PM PST Mon Dec 8 2025

.SYNOPSIS...
A strong atmospheric river has moved into the region, and will
bring periods of moderate to heavy rainfall and gusty winds to
western Washington through Wednesday. There remains high risk
of widespread and significant river flooding across the region
through much of the week. Minor coastal flooding due to high
astronomical high tides will also remain possible for the Salish
Sea coastlines through the first part of the week. Wet and
unsettled conditions will continue through the end of the week.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

Precipitation associated with a strong atmospheric river has
moved into the Pacific Northwest this afternoon, and is expected
to affect the region directly through Wednesday, and indirectly
through the remainder of the week. The key messages regarding
this system are highlighted below:

* HEAVY RAIN: Extended periods of moderate to heavy rain to
  western Washington through Wednesday. Latest forecast models
  have remained fairly consistent, with the heaviest rainfall
  arriving today. The moisture plume still looks to briefly
  shift southward early Tuesday, easing accumulations for some
  areas before lifting back northward late Tuesday through
  Wednesday. While areas east of the Olympics will likely see
  some shadowing at the onset of precipitation, conditions
  across all of western Washington will be very wet through
  Wednesday. Areas generally south of Seattle will see 3 to 6
  inches of rainfall through Thursday morning in a 72 hour
  period, with the Olympics and Cascades on track to see 8 to 12
  inches of rain in this timeframe. Locally higher amounts are
  possible over the southern and central Cascades, where amounts
  could reach 15 inches or more in 72 hours. This is expected
  to bring significant river flooding to western Washington,
  with many area rivers forecast to reach moderate or major
  flood stage by mid-week. A Flood Watch remains in effect for
  all of western Washington through Friday morning. For more
  details, see the HYDROLOGY section below.

* WIND: Conditions will be windy area-wide today, with
  southwesterly winds picking up throughout the day. Winds will
  peak late in the afternoon and evening, with the strongest
  gusts along the Pacific Coast reaching 50-55 mph. Gusts
  elsewhere across the interior will reach 40-45 mph at times.
  Winds will gradually ease into Tuesday, but conditions will
  remain breezy at times.

* COASTAL FLOODING: Minor coastal flooding remains possible
  along the Salish Sea coastlines through the first half of the
  week with high astronomical tides. While the tides will
  generally remain below or nearing thresholds, heightened river
  flows or wind effects could exacerbate inundation in some
  areas around high tide.

In addition, snow levels will briefly lower to near 3500-4000
feet over the mountains early Tuesday, resulting in
minor accumulating snow generally above 4500 feet. The higher
mountain passes, including Stevens Pass and White Pass, will
likely see a few inches of snow accumulation throughout the day
Tuesday which could cause brief slippery travel conditions.

The returning surge of moisture later Tuesday afternoon will
bring warmer temperatures and higher snow levels through the
week. Temperatures will peak well above normal most days this
week, with temperatures in the low to upper 50s across the
lowlands.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Unsettled conditions continue to be expected into the weekend,
though precipitation amounts will start to taper across western
Washington by Thursday. It is likely that impacts like lingering
river flooding and elevated landslide risk will linger through
Thursday for many areas. Ensembles a system likely to brush the
area Thursday, with extended long range ensembles hinting at a
break Friday, followed by another stronger system likely
focused to the north over British Columbia early Saturday and
then possibly Western Washington Saturday into Sunday.

15

.AVIATION...
The first frontal system from an atmospheric river continues to
progress across the terminals this afternoon. Moderate to heavy rain
will continue to fall across the terminals this afternoon and
evening, with varying reduced visibilities down to 2-4 SM, and
ceilings continuing to vary between MVFR and IFR. Winds will also
peaking this afternoon with gusts out of the southwest with gusts up
to 30-40 kt being observed. Later this evening, NW winds will pick
up in the Strait of Juan de Fuca. The diffluence from the winds will
likely turn winds NW in the Puget Sound terminals from 06-12Z. All
winds will decrease down to 5-10 kt out of the south late
tonight/Tuesday morning. MVFR to IFR cigs will continue into Tuesday
morning, with lower visibilities (mist) also lingering into Tuesday
morning in the south interior and coast. Ceilings will improve to
MVFR/VFR through the day. Next round of moderate to heavy rain will
arrive from the SW from 22Z Tuesday onwards, with ceilings lowering
to IFR, reduced visibilities, and SW winds increasing again to 20-30
kt late Tuesday.

KSEA...Low MVFR/IFR will continue through the evening with rain
lingering through Tuesday morning (~12Z). Some of the rain may be
heavy at times, reducing visibilities down to IFR. SW winds 15-20 kt
gusting to 30 kt will continue through the evening. A period of N
winds is likely from 06Z-12Z (due to diffluence from the Strait of
Juan de Fuca), with gusts up to 20 kt still possible as winds turn,
but should decrease to 6-10 kt. From 12Z onwards, south winds 6-10
kt gusting to 15 kt will continue through 20Z, with winds decreasing
to 4-8 kt. Another round of gusty winds are expected after 00Z 10-15
kt gusting to 25 kt. MVFR ceilings will continue through tonight and
into Tuesday. Moderate to heavy rain arrives with round 2 around 00Z
Wednesday.

HPR

&&

.MARINE...
The first frontal system from an atmospheric river continues to
impact area waters today. The areas with the breeziest SW winds this
afternoon are the coastal waters and the interior waters. As the
cold front kicks in, strong west winds will pick up in the Strait of
Juan de Fuca through tonight. The wind threat will end early Tuesday
morning across all waters as winds decrease behind the cold front.
Hazards were adjusted to account for the extended duration of winds
behind the front, and also seas of 10-15 ft dropping to 9-12 ft
Tuesday. Heavy rain will continue tonight into Tuesday morning,
which may reduce visibilities at times. The next system arrives late
Tuesday night through Thursday, with more moderate to heavy rain,
breezy winds southwest winds (most likely remaining below gale force
at this time, but most hazardous to small craft), and seas remaining
above 10 ft through Thursday at 9-11 ft, decreasing to 4-6 ft Friday
through Saturday. Another system will increase seas and winds early
next week.

HPR

.HYDROLOGY...
A strong atmospheric atmospheric will move through
the Pacific Northwest through Wednesday, bringing significant
heavy rainfall across the area. 72-hour precipitation amounts
between ending Thursday morning will likely reach 2 to 6 inches
across the lowlands, with 6 to 10 inches over the Olympics and
Cascades with locally higher amounts up to 12 inches over the
central and southern Cascades. Rivers will start to sharply rise
tonight, with many area rivers reaching flood stage by later
this evening. Confidence remains high that a widespread
significant river flooding event will commence late Monday and
continue through much of the week.

Many rivers flowing off the Cascades and the Olympics are
forecast to reach Minor, Moderate, and Major flood stage between
this evening and Tuesday, where many of them are forecast to
remain through Thursday. While some uncertainty does still
remain in regards to the exact flood levels and stages through
the next week, it will be critical to monitor the forecasts now
and through the next seven days. Additional precipitation is
also possible Thursday into Friday, which may keep rivers
elevated heading into the weekend. A Flood Watch remains in
effect across all of western Washington through Friday.

With the wet antecedent soil conditions, the landslide threat
across the region will increase with this system. Potential has
also increased for debris flows over area burn scars, which will
continue to be monitored.

Urban and small stream flooding, as well as areas with poor
drainage, should be alert to the potential for localized nuisance
flooding and ponding on roadways. Low water crossings may become
impacted or impassable.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Wind Advisory until 10 PM PST this evening for City of Seattle-
     Downtown Everett / Marysville Area-Eastern Kitsap County-
     Eastern Strait of Juan de Fuca-Eastside-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-Foothills and
     Valleys of Thurston and Lewis Counties-Foothills and
     Valleys of the North Cascades-Foothills of the Western
     and Southern Olympic Peninsula-Grays Harbor County Coast-
     Island County-Lake Crescent Area Including US 101-Lower
     Chehalis River Valley-Lowlands of Lewis and Southern
     Thurston Counties-Lowlands of Pierce and Southern King
     Counties-Lowlands of Western Skagit and Northwestern
     Snohomish Counties-Lowlands of Western Whatcom County-
     Middle Chehalis River Valley-Northern Hood Canal-Northern
     Washington Coast-Olympia and Southern Puget Sound-Port
     Townsend Area-San Juan County-Shoreline / Lynnwood /
     South Everett Area-Southern Hood Canal-Western Strait of
     Juan de Fuca-Willapa and Black Hills.

     Flood Watch through Friday afternoon for Cascades of Pierce
     and Lewis Counties-Cascades of Snohomish and Northern
     King Counties-Cascades of Southern King County-Cascades
     of Whatcom and Skagit Counties-City of Seattle-Downtown
     Everett / Marysville Area-Eastern Kitsap County-Eastern
     Strait of Juan de Fuca-Eastside-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-Foothills and Valleys of
     Thurston and Lewis Counties-Foothills and Valleys of the
     North Cascades-Foothills of the Western and Southern
     Olympic Peninsula-Grays Harbor County Coast-Island County-
     Lake Crescent Area Including US 101-Lower Chehalis River
     Valley-Lowlands of Lewis and Southern Thurston Counties-
     Lowlands of Pierce and Southern King Counties-Lowlands of
     Western Skagit and Northwestern Snohomish Counties-
     Lowlands of Western Whatcom County-Middle Chehalis River
     Valley-Northern Hood Canal-Northern Washington Coast-
     Olympia and Southern Puget Sound-Olympics-Port Townsend
     Area-San Juan County-Shoreline / Lynnwood / South Everett
     Area-Southern Hood Canal-Western Strait of Juan de Fuca-
     Willapa and Black Hills.

PZ...Small Craft Advisory until 7 PM PST Tuesday for Grays Harbor
     Bar.

     Gale Warning until 1 AM PST Tuesday 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.

     Small Craft Advisory from 1 AM to 7 PM PST Tuesday 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 7 AM PST Tuesday for Central U.S. Waters
     Strait Of Juan De Fuca-East Entrance U.S. Waters Strait
     Of Juan De Fuca.

     Gale Warning until 4 AM PST Tuesday for Admiralty Inlet-
     Northern Inland Waters Including The San Juan Islands.

     Gale Warning until 2 AM PST Tuesday for Puget Sound and Hood
     Canal.

&&

$$