PORTLAND, Ore. – The National Weather Service's "flood watch" for Northwest Oregon and Southwest Washington will run from Saturday afternoon to Monday morning.
"Many rivers will rise sharply today, with flooding possibly as early as late this afternoon," the National Weather Service reports. "Flooding of creeks and ponding in urban areas is also likely."
The flood watch includes a warning about possible landslides and debris flows of danger: "People, structures and roads located below steep slopes, in canyons and near the mouths of canyons may be at serious risk from rapidly moving landslides."
The flood watch includes the Portland and Vancouver areas, areas of Interstate 5 in Southwest Washington, and the north and central Oregon coast and coast range.
"Heavy rain today will drive river levels up sharply starting this afternoon and continuing into Sunday," the weather service predicts. "Several rivers may reach flood stage as early as this afternoon, with the flood threat continuing into Monday.
"Southwest Washington rivers of most concern include the Grays River in Wahkiakum County and the Cowlitz River in Cowlitz County," the weather service reports.
Northwest Oregon rivers of most concern include:
- Johnson Creek in Multnomah County
- Upper Tualatin River in Washington County
- Pudding River in Clackamas and Marion Counties
- Cowlitz River at Kelso in Washington's Cowlitz County
- Luckiamute River in Polk and Benton counties
- Nehalem River in Tillamook County
- Wilson River in Tillamook County
- Trask River in Tillamook County
- Siletz River in Lincoln County
This flood watch comes as a "moist storm system and warm front" brings heavy rain to much of northwest Oregon and Southwest Washington Saturday. The weather service predicts additional "periods of heavy rain" on Sunday and Monday as a cold front slowly moves south.
The heaviest rain is likely to be in the north Oregon coast range, Willapa Hills and the south Washington Cascade mountains, with 6-hour amounts as high as 3 inches and 24-hour amounts as high as 6 inches predicted.
"There is an expected break in the rainfall on Sunday, especially in Oregon," NWS predicts. "And then the cold front will bring additional rainfall from Sunday afternoon through Monday."
Freezing levels are expected to be above 6,000 feet, which means the Portland area should not be affected by ice and other freezing byproducts. See "What's your elevation?"
Here are the areas where the National Weather Service reports flooding is likely to occur:
- Greater Portland-metro area
- Greater Vancouver area
- The Interstate-5 corridor in Cowlitz County
- Central Willamette Valley
- South Willamette Valley
- Western Columbia River Gorge
- Northern Oregon Cascade foothills
- Northern Oregon Cascades
- Upper Hood River Valley
- South Washington Cascades
- Willapa Hills
- South Washington Coast
- South Washington Cascade foothills
- North Oregon coast
- Central Oregon coast
- Coast range of northwest Oregon
- Central coast range of western Oregon
- Lower Columbia
- The cities and tourist areas of Astoria, Cannon Beach, Tillamook, Lincoln City, Newport, Florence, Vernonia, Jewell, Trask, Grande Ronde, Tidewater, Swisshome, St. Helens, Clatskanie, Hillsboro, Portland, Oregon City, Gresham, Salem, McMinnville, Dallas, Eugene, Corvallis, Albany, Hood River, Cascade Locks, Multnomah Falls, Sandy, Silver Falls State Park, Sweet Home, Government Camp, Detroit, Santiam Pass, Parkdale, Odell, Coldwater Ridge Visitors Center, Mount St. Helens, Frances, Ryderwood, Raymond, Long Beach, Cathlamet, Longview, Kelso, Castle Rock, Stevenson, Skamania, Vancouver, Battle Ground, Washougal, Toutle, Ariel and Cougar, Wash.
The flood watch remains in effect from noon Saturday through Monday morning for all of northwest Oregon and Southwest Washington.
Accumulating snow is possible at higher elevations late Monday night and Tuesday.
Watch our team coverage of Saturday's flooding: