San Francisco residents woke up early Saturday morning to a tornado warning during a powerful storm system that lashed the region with heavy rain and wind.
The National Weather Service issued a warning for northern San Mateo County and parts of downtown San Francisco just before 6 a.m.
According to the NWS, there was a cyclonic signature on the radar that had produced enough of a rotational signature to trigger the warning.
The warning ended at 6:07 a.m. for San Francisco as the storm moved northeast of downtown. The warning for the rest of the area expired at 6:20 am
The warning prompted a flood of messages on social media from residents who woke up to the alert on their cell phones. It was reported as the first-ever tornado warning for San Francisco.
A special warning was also issued for a possible water spout in San Francisco Bay in the Bay Bridge area, which expired ten minutes after the tornado warning.
Although the strongest part of the system has passed, isolated severe thunderstorms remain possible throughout the morning in parts of the Bay Area, the National Weather Service said.
The risk of a severe storm is marginal and the NWS says it will only last through Saturday morning. According to PG&E, the storm conditions caused power outages for thousands of people in the Bay Area.
