A series of atmospheric river storms will continue to drench Washington this week, prompting widespread flood watches and landslide concerns across the region, the National Weather Service said.
The heaviest rain is expected through Wednesday, but many flood watches issued Monday morning remain in effect through Friday, as rivers, creeks and saturated hillsides respond to days of steady moisture.
Flooding forecasts of local rivers
Forecasts from the Northwest River Forecast Center show several Western Washington rivers with the potential for sharp rises as heavy rain continues this week.
While exact river levels will depend on how much rain falls in the mountains, hydrologists say the combination of saturated soils, persistent rainfall and additional runoff from higher elevations puts a number of river basins at elevated risk.
The Skagit River, particularly near Concrete, is one of the systems forecasters are watching closely. The river responds quickly to prolonged mountain rainfall, and historic flood patterns in the upper basin make it one of the region’s more flood-prone waterways during atmospheric river events.
The Snohomish River system — including its major feeder, the Skykomish River — is also at risk of significant rises. Water from steep western Cascade slopes can move rapidly into the Snohomish basin, and emergency managers have noted the potential for the river to approach flood stage if heavy rain persists through midweek.
Farther south, the Snoqualmie River could also see considerable impacts. The river’s middle and lower valleys tend to flood when prolonged rainfall saturates foothill soils, and forecasters say this week’s storm track creates conditions similar to past high-water events.
The Cowlitz River in southwest Washington is another basin with rising concern, especially where rainfall in the Cascade foothills and coastal mountains funnels into the lower Columbia region. Forecast models show the river capable of reaching levels associated with at least minor flooding if rainfall rates reach the higher end of projections.
In addition to major rivers, hydrologists warn that smaller creeks and tributaries draining the Olympics and Cascades may rise quickly, leading to localized flooding in areas with limited drainage or steep terrain. Those waterways often react the fastest during atmospheric river events, especially where recent rainfall has already saturated the ground.
Western Washington under flood watch through Friday
The National Weather Service in Seattle kept its Flood Watch in effect for 14 counties in northwest and west-central Washington, including King, Pierce, Snohomish, Thurston, Kitsap, Mason, Lewis, Clallam, Jefferson, Grays Harbor, Island, San Juan, Skagit and Whatcom counties.
The watch covers major cities such as Seattle, Tacoma, Olympia, Everett, Bellingham, Bremerton and Mount Vernon.
Forecasters warn that excessive rainfall may cause rivers, creeks and streams to overflow, with urban areas also at risk where storm drains clog with leaves or debris.
Many waterways are already running high after several days of rain.
“Sharp rises will be possible on area rivers, especially those flowing off the Olympics and Cascades,” NWS said.
Central Washington joins flood alerts as rain hits snowpack
The National Weather Service in Pendleton issued a new Flood Watch for parts of Kittitas County, Yakima County, and the southern Washington Cascades, where rivers like the Naches, Yakima and Klickitat are expected to see substantial rises.
This watch runs from 7 a.m. Monday through Friday morning, with forecasts showing area rivers and streams reaching their highest levels between Wednesday and Friday.
Chelan County: Rain on snow increases flood and slide danger
Chelan County is also under a Flood Watch from the Weather Service in Spokane, which warns of rainfall combined with snowmelt below 7,000 feet.
Forecast rainfall totals of 1.5 to 4 inches could lead to flooding in smaller rivers and creeks, along with a heightened risk of rock and mud slides, especially near steep terrain and burn scars.
Widespread landslide threat across Western Washington
In addition to the flood watches, a Special Weather Statement issued by the Weather Service in Seattle warns that the prolonged rain will significantly increase the risk of landslides and debris flows across Western Washington from Monday through at least Wednesday, with lingering danger afterward.
Soils across the region are already saturated from 1 to 4 inches of rain in recent days.
Another 2 to 6 inches in the lowlands and 4 to 10 inches in the mountains is expected through midweek.
The areas most prone to landslides include:
- Steep coastal bluffs
- Steep hillsides and road cuts
- Recently burned terrain
Residents urged to monitor conditions
Forecasters urge people in flood-prone or landslide-prone areas to remain alert through the week, watch for rising rivers, and be ready to take action if warnings are issued. Drivers are advised to avoid standing water and remain cautious on rain-soaked roads.