A Pacific storm aiming first for the northern half of California and then moving south is picking up moisture from the tropical Pacific, making it a potent atmospheric river of precipitation also known as a “pineapple express that will bring wet and severe winter-like weather to much of the United States as it moves across the country.
The severe weather, including flooding and high winds, could impact 108 million people from storms that began late Saturday are expected to last well into Tuesday. Seven million people were under flash flood alerts in California and Nevada, where as much as 10 inches of rain was possible, according to NBC News forecasters. From the “bomb cyclone” accumulating off of the Oregon coast to heavy rains in the mid-Atlantic region, varying temperatures will cause potentially deadly results. Still, the impending storm could challenge federal forecasters’ warnings that a La Niña weather pattern for California will bring more bad news — a relatively warm, dry winter.
In California alone, rates of rainfall from the storm could exceed one-half inch per hour, leading to life-threatening flash floods and mudslides in areas where burn scars were created by recent wildfires. The National Weather Service in Oxnard tweeted that Sunday night into Monday, Southern California residents should expect “gusty winds, rain, and possibly minor flooding and debris flows in recent burn areas” while waves as high as 30 feet were forecasted for parts of the Northern California coast. And the state’s Sierra Nevada mountains could also experience winds as fast as 100 mph, which could make travel nearly impossible, take down trees, and cause power outages. NBC News weather forecasters also say as much as 3 feet of snow could fall in the highest elevations.
— Rob Mayeda (@RobMayeda) October 23, 2021
The Sunday storm comes after Gov. Gavin Newsom expanded the state’s drought emergency to cover all California counties. In a statement Tuesday, the governor noted that the western U.S. faced a potential third year in a row of drought. Water experts say the Pacific storm won’t end the drought, but it could help replenish the state’s ailing water supply.
Forecasters warn that the storm that follows on Sunday is likely to be the strongest of the entire storm train and will undergo rapid intensification as another bomb cyclone. https://t.co/Gw8iEHoGia pic.twitter.com/2D4mFCG89W
— Breaking Weather by AccuWeather (@breakingweather) October 23, 2021
The front was expected to strike Baltimore, Washington, D.C., and the mid-Atlantic by Tuesday morning, forecasters said. Rain and freezing conditions were possible, they said. As many as 53 million people on the east coast could be impacted by the unsettled system.
— US StormWatch (@US_Stormwatch) October 24, 2021