Heavy rain on Sunday is expected to cause life-threatening flash floods and mudslides in parts of Northern California already besieged this year by droughts and wildfires, the results of extreme weather brought on by human-induced climate change.
A series of low-pressure systems from the Pacific Ocean could produce up to 10 inches of “much needed precipitation” in the region, according to the Weather Prediction Center of the National Weather Service.
But the rain could fall at a rate of up to one inch per hour, increasing the likelihood of dangerous mudslides and flash floods, especially over burn scars left by the recent wildfires, said Julie Malingowski, a meteorologist at the National Weather Service.
“The vegetation is not there to absorb the rainfall like it normally would, so these areas are a lot more susceptible,” she said.
The Weather Service described the storm systems as “atmospheric rivers” — long, narrow columns in the atmosphere, like rivers in the sky, that move water vapor out of the tropics. The vapor is released as rain or snow when it makes landfall.
The atmospheric river event could last until Tuesday, when it moves into the Great Plains, the service said.
The precipitation will turn to snow in many of the western mountain ranges in the state. In the Sierra Nevada, there could be at least two feet of snow, according to the prediction center. That is welcome news for a state that relies on reserves of snow to store water.
“There is a huge upside” to the heavy precipitation, Ms. Malingowski said. “California has been in an extreme to exceptional drought, and this kind of rainfall will help to mitigate this kind of drought.”
On Tuesday, Gov. Gavin Newsom issued a proclamation extending the drought emergency statewide and asked residents to redouble their water conservation efforts amid an exceptionally dry year in which wildfires have ravaged large stretches of the state.
This year has been the second driest on record in state history, with near record low storage in California’s largest reservoirs, the governor’s office said.
Severe drought conditions, worsened by climate change, continue to affect much of the Western United States and even the northern part of the Great Plains.
While droughts are not uncommon in the region, scientists say that climate change, in the form of warming temperatures and shifts in precipitation, is making the situation worse.
In California, there are at least seven large wildfires currently burning, including the Dixie fire, the second-largest in state history, which has burned more than 960,000 acres, destroyed 1,300 buildings and killed one firefighter, according to a New York Times wildfire tracker.
Since the start of the year, wildfires across California have burned more than six million acres.