The northern Willamette Valley and southwest Washington could still see snow.
The heavy rain has raised concerns about landslides in steep areas and the burn scars of wildfires, as well flooding in urban streams and some rivers in the Central and Southern Willamette Valley.
"Heavy precipitation Monday night through Tuesday will likely fall as rain at lower elevations, although uncertainty remains about the snow level Tuesday morning," the National Weather Service in Portland said. "Rainfall totals of 1 to 4 inches are possible for the coast and inland valleys. The combination of low-elevation heavy rain and snowmelt may result in localized small stream and urban flooding, along with flooding along a few rivers and creeks in the Willamette Valley Tuesday and Tuesday night."
"Heavy rain can trigger landslides and debris flows in steep terrain, and the risk is higher in burn areas," the Department of Geology and Mineral Industries noted Monday. "Debris flows are rapidly moving, extremely destructive landslides. They can contain boulders and logs transported in a fast-moving soil and water slurry down steep hillsides and through narrow canyons. They can easily travel a mile or more. A debris flow moves faster than a person can run. People, structures and roads located below steep slopes in canyons and near the mouths of canyons may be at serious risk."
Forecasters issued a Flood Watch, in effect from 7 p.m. Monday night through late Tuesday night.
"Rivers of greatest concern include the Marys in Benton County, the Luckiamute in Polk and Benton counties, and Johnson Creek in Multnomah and Clackamas County," forecasters said. "As of Monday morning, only minor flooding is predicted."
Higher elevations will likely still see snow.
GOT SNOW? Share Your Videos & Photos
Forecasters issued a Winter Storm Watch for Veneta and the surrounding Central Coast Range, in effect from 6 p.m. Monday to late Tuesday night.
The forecast calls for up to a foot of new snow above 1,500 feet, with wind gusts up to 35 on exposed ridges.
"Heavy, wet snow may result in broken tree limbs and power lines, raising the chance of isolated power outages," forecasters said Monday. "Travel may become very difficult, especially in the hills. Be sure to carry chains if you must travel tonight, Tuesday, or Tuesday night."
"Heavy snow expected. Total snow accumulations of 2 to 5 inches in the foothills below 1500 feet and 8 to 15 inches in the foothills between 1500 and 2500 feet," forecasters said.