The West Coast’s rainy season has arrived in force, as an atmospheric river carrying moisture from the tropics joins a bomb cyclone off the Pacific Northwest coast. Heavy, wet snow began falling in the mountains on Nov.

A bomb cyclone that hit the US Pacific north-west and killed multiple people is expected to combine with an atmospheric river, bringing life-threatening rainfall and flooding to the western region. The winter storm has already brought damaging winds and dangerous levels of rain and snow to the US west coast.