Southern California is experiencing severe flooding and mudslides due to a powerful winter storm and atmospheric river, prompting Governor Gavin Newsom to declare a state of emergency in several counties. Coastal areas are bracing for months' worth of rain, with risks of flash flooding, debris flows in wildfire-scarred regions, and power outages affecting thousands. Evacuations have been ordered in vulnerable communities, and authorities are urging residents to stay off roads due to hazardous conditions. The storm is expected to continue through the holiday weekend.