California was bracing Thursday for the arrival of another atmospheric river that forecasters warned will bring downpours, strong winds, thunderstorms and the threat of flooding to a state that has not yet fully recovered from previous storms.
The threat of flooding will come from a combination of rain and the melting of some of the enormous snowpack packed in the California mountains from the passage of nine atmospheric rivers in early winter and subsequent storms fueled by a blast of arctic air.
The new atmospheric river is of the type known as the “Pineapple Express,” as it is a deep tap of warm subtropical moisture that stretches from the Pacific Ocean to Hawaii. Its greatest impact is expected to be in northern and central California.
The accumulation of snow at high altitudes is such that it is expected to absorb rain, according to meteorologists. But elevations below 4,000 feet (1,219 meters) will experience melting and runoff. The National Weather Service rated the threat of flooding as “moderate.”
For the higher elevations, the storm is forecast to drop a large amount of snow, up to 2.4 meters (8 feet) in some places.
Snowpack in California’s Sierra Nevada, which provides about a third of the state’s water supply, is more than 180% above average for April 1, when it historically peaked.
So much snow has fallen in the Sierra and other mountain ranges that residents are still struggling to stay afloat days after previous storms.
Roofs collapsed, cars were buried, and roads were blocked. Governor Gavin Newsom declared an emergency in 13 of California’s 58 counties effective March 1.
In the San Bernardino Mountains east of Los Angeles, a late February storm reached blizzard status. Mountain towns like Lake Arrowhead were engulfed.
“We’ve been through a lot of snowstorms, but none of this magnitude, that’s for sure,” Alan Zagorsky, a 79-year-old resident, said Wednesday as a crew shoveled his driveway. “Right now, they’re trying to find a place where they can put this.”
