UC Berkeley Central Sierra Snow Lab and National Weather Service reports

Atmospheric River Brings Heavy Rain, 60 mph Winds, and First-Ever Tornado Warning to Bay Area

Dec 14, 2024, 12:02 PM

A powerful atmospheric river storm descended upon the San Francisco Bay Area over the weekend, bringing heavy rain, strong winds reaching up to 60 mph, and raising the risk of flooding in low-lying areas. The National Weather Service issued flood and wind watches for parts of the region as the Level 2 storm arrived Friday evening, peaking Saturday morning. Coastal flood advisories were also in effect due to king tides and high surf, with waves up to 22 feet expected along Bay Area beaches. In an unusual event, a tornado warning was issued for San Francisco early Saturday morning, marking the first such warning on record for the city. The storm also carried a marginal risk of severe thunderstorms, with potential for urban flooding. The Sierra Nevada was heavily impacted, with winter storm warnings issued for Interstate 5 over Mount Shasta and Interstate 80 over the Sierra, where forecasts predicted up to 3 feet of snow by Sunday, making travel difficult to impossible. The UC Berkeley Central Sierra Snow Lab expected 2 to 4 feet of snow, further indicating the storm's intensity.