In addition to more rain, strong winds and mountain snow were expected across the Cascades, Sierra and northern Rockies, the National Weather Service said.

In Oregon, where two women died in storm-related accidents, Governor Kate Brown declared a state of emergency for 13 counties.

This week's unusually powerful storms broke at least five weather records for the Seattle area, including the wettest first nine days in December, forced the closure of an interstate highway and swamped dozens of streets and bridges.

Emergency management officials in both Washington and Oregon have warned of more mudslides after days of ground saturation.

In a rare event for the Pacific Northwest, the National Weather Service on Thursday said it had received reports of a moderate-strength tornado in Battle Ground, Washington. Television footage showed residents clearing debris from roads and blue tarps covering damaged roofs.

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