The forecast shows a wet week ahead with up to 3 inches of precipitation possible on Wednesday and Thursday in some areas.
“The main concern is that the snow level is looking to rise and with more rain, that’s going to run off into the rivers and probably cause some rivers to flood,” said Johnny Burg, a meteorologist with the National Weather Service.
The rivers most at risk are the Skokomish, Snoqualmie and Chehalis but a section of the Puyallup River in Orting is also being monitored. Forecasters said the lowlands will likely see 1 ½ to 2 inches Wednesday and Thursday.
Just over an inch of rain had fallen at Sea-Tac Airport by Monday afternoon, the Weather Service said.
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Several landslides in the North Bend area helped prompt the issuing of a special weather statement warning about unstable hillsides.
“Cumulative rainfall over the last week has soaked soils to the point where the Washington landslide risk is at elevated levels,” the statement said.
Higher elevations were faring no better as snow fell in force. The road to Paradise in Mount Rainier National Park remained shuttered Monday due to avalanche danger and Interstate 90 over Snoqualmie Pass was closed most of the day for avalanche control. The Pass could be open by 4:30 p.m., officials said.
Bart Treece, a spokesman for the Transportation Department, said recent layers of heavy snow are unstable because of warming temperatures.
Rangers at Mount Rainier reported 18 inches of powder from Sunday to Monday.
More snow and sleet is expected in the mountains this week. The snow level in the Central Cascades was near 3,000 feet Monday and expected to rise to 5,000 feet within days.