A cold, late-winter Pacific storm brought rain and snow to California on Tuesday. Winter storm warnings were posted or scheduled to take effect during the day in mountains from the Oregon border south to the U.S-Mexico border. Mountain travel was discouraged due to the potential for major delays, chain controls and near-whiteout conditions, the National Weather Service said. The San Francisco Bay Area weather office warned of possible hail, thunderstorms and downpours that could make driving risky.