New Delhi, Dec. 11 -- Heavy rain continued to push across Washington State and southern British Columbia on Thursday, forcing new evacuations and closing several major routes. Officials warned that some rivers were rising faster than expected, creating conditions that could rank among the region's most serious flood events in decades.

Residents along the Skagit River northeast of Seattle, and the Puyallup River closer to Tacoma, faced evacuation orders overnight. State officials said that as many as 100,000 people could receive similar instructions if the waters continue to rise.

Governor Bob Ferguson issued an emergency declaration late Wednesday and activated the National Guard, with about 300 members standing by for flood-response re...