California monster El Niño storm to bring up to three feet of snow
California is being targeted by a monster El Niño storm that will bring seven days of torrential rain and up to three feet of mountain snow and may cause an Oroville Dam overflow.
A period of strengthening trade winds that seemed set to end this year's El Niño that brought a record 188 percent of average snowpack to California's Sierra Mountains reversed in mid-April to surge a bloom of heated water along the Equatorial Pacific and reawaken a late-season El Niño that has a 70% probability of lasting through the summer.
The upper atmosphere jet stream normally blows east to west at about 100 miles per hour across the Pacific Equator bringing torrential rains to Polynesia before curving up Asia, curving past Japan to Alaska, and dropping down along the West Coast. But the jet stream has radically bent down and accelerated to 200 miles an hour to directly target California with the full load of Polynesia's monsoon rains beginning on Wednesday.
Rainfall for the month of May normally averages just a quarter-inch in Los Angeles and a half-inch in San Francisco. But this storm is expected to dump at least 1 to 2 inches along the coasts, 4 inches inland, and up to 36 inches of snow at higher elevations.
The surprise storm train, coming as all four Northern California reservoirs along the Sierras are already filled to 94 percent of capacity, will require opening their spillway gates, potentially flooding valley croplands and large population centers downstream.
The California Department of Water Resources announced that the water level at the 899-foot Oroville Dam is at 890 feet, just nine feet from overflowing. A $1.1-billion rebuild of the main spillway that washed away in an El Niño downpour February 2017 and almost caused the catastrophic collapse of America's tallest earthen dam is still not completed.
Butte County sheriff Kory Honea, who at the height of the crisis took control to call the emergency evacuation of 188,000 downstream residents who could have faced a 30-foot wall of water if the dam collapsed, joined DWR officials and reconstruction contractors to tour the dam and the supporting public safety infrastructure on Tuesday.
DWR's public information officer stated that the California-owned dam's staff shared information about the operations plan and engineering and design features that are part of the two-year reconstruction project.
AccuWeather senior meteorologist Alex Sosnowski warned California residents that in addition to drenching rain, hail, wind gusts, and mountain snow, there is risk of brief tornadoes and waterspouts.