A flood warning was issued through this morning for Alsea and other areas in western Benton County, and the Marys River was predicted to swell to major flood levels today.

Heavy rains - as much as six inches on Sunday in some parts of the Coast Range - and snowmelt from warm temperatures have added runoff to river levels, according to the National Weather Service.

The Marys, Alsea and Luckiamute were among the rivers listed as most at risk for flooding by the agency.

A flood warning means that flooding is imminent or has been reported.

A flood watch, which means there is a potential for flooding, also was issued through late tonight for much of western Oregon, including Corvallis, Albany and Sweet Home.

The Marys River level near Philomath was forecast to increase to 20.89 feet by noon today. That's just short of its highest crest recorded ever of 21.11 feet on Dec. 30, 2005, according to the agency.

"This looks like a short event, which is a good thing," said Peggy Peirson, Benton County emergency services coordinator. The Marys River is forecast to drop quickly to below bank full level of 16 feet on Sunday.

The flood stage for the Marys is 20 feet, and its major flood stage is 20.7 feet. If the latter is reached, residents should expect some roads to be flooded, especially near Chapel Drive and Grange Hall Road, south of Philomath.

Portions of Highway 99W in Corvallis also have historically been flooded at that level.

By noon on Saturday, the Willamette River at Corvallis was predicted to rise above its bank full level of 16 feet to 17.5 feet.

The Willamette River's flood level near Corvallis also is 20 feet. However, if the water reaches 18 feet or higher at Corvallis, widespread flooding of county roads and road closures can be expected, according to the National Weather Service.

The Long Tom River at Monroe was expected to crest at 7.95 feet at 4 p.m. today. The bank full level there is 8.5 feet.

According to agency's flood watch statement, those living in areas prone to flooding should be prepared to take action.

Landslides and debris flows are possible during this storm event. People in structures or on roads at the bottom of steep slopes, or those in canyons or at the mouth of canyons, might be at serious risk from rapidly moving landslides.

Peirson urged people to watch for standing water on roadways and to obey emergency road signs. "If they close a road, they close it for good reason," she said.

She also asked people to make sure that culverts and storm drains are clear, even in the city, to prevent flooding.

The National Weather Service also issued a high wind watch for the central and south Willamette Valley through this morning, predicting that sustained winds of up to 35 mph and gusts of up to 55 mph were possible.

Kyle Odegard can be contacted at kyle.odegard@lee.net or 758-9523.