The ninth in a three-week series of major winter storms is churning through California. Mountain driving remains dangerous and flooding risk is high near swollen rivers, even as the sun has come out in some areas. Heavy snow continues to fall across the Sierra. The National Weather Service is discouraging travel. A barrage of atmospheric river storms has dumped rain and snow on California since late December, cutting power to thousands, swamping roads, unleashing debris flows, and triggering landslides.