The first storm was forecast to linger into the weekend and produce an additional 6-12 inches of rainfall, the weather service said. An atmospheric river prompted a high-risk warning for excessive rainfall along the Northern California coast.

Bomb cyclones form when a storm's atmospheric pressure drops sharply within 24 hours in a process called bombogenesis.

Forecasters said a final round of rain, snow and high winds were targeting the Pacific Northwest and Northern California regions on Friday.