A powerful storm system is bringing flooding, landslides, and heavy rains and snow to California, with the National Weather Service issuing a warning for the upper elevations of the Sierra from south of Yosemite National Park to north of Lake Tahoe. The Susan River is forecast to rise significantly, potentially affecting homes, roads, and bridges, while Sacramento fire officials plan to broadcast evacuation announcements from a helicopter and a boat. Humboldt County, which was hit by an earthquake last week, is also seeing roadways beginning to flood, with a bridge potentially closing again if the Eel River gets too high.