Two strong storm systems are expected to batter the East and West coast simultaneously starting Monday as California faces a fresh threat of flash flooding and heavy mountain snow.
The arrival of the pair of “separate but potent” low-pressure systems has left 22 million people under winter weather alerts and will see both sides of the country slammed with severe weather this week, with widespread precipitation linked to a system across the Pacific Northwest expected to move southward into California, the National Weather Service said.
The system, fueled by an atmospheric river, is expected to slam onshore into the already storm-battered state on Monday across northern California, and eventually bring heavy rain to central and southern California on Tuesday. Around 17 million people across northern and central California were under flood watch Monday, and southern parts of the state will likely be added to the flood watch list.
Heavy snow is also forecast for higher elevations of the Sierra Nevada, the agency said.
Rainfall amounts could reach 6 to 8 inches in parts of the foothills and mountains in the Sierra Nevada and also southern California over the next 24 to 72 hours. Snowfall amounts will be up to 4 feet above 7,000 feet and 8 feet above 9,000 feet.
“Considerable flooding impacts” are also expected below 5,000-foot elevation along the central California coast, San Joaquin Valley, Sacramento Valley, and southern Sierra Nevada foothills into Tuesday, it said.
Areas most likely to see isolated flooding Monday include Eureka, Redding and Santa Rosa, California.
The weather service further warned that heavy rain and snowmelt could lead to renewed and more widespread flooding, particularly in low elevations.
“Some heavy snow can also be expected farther inland across the Intermountain West, especially central Idaho and western Wyoming,” it said.
The latest round of severe weather comes following major flooding over the early weekend that saw dozens of people rescued by first responders and the California National Guard, according to The Associated Press.
One video showed a member of the Guard helping a driver out of a car trapped by water.
California Gov. Gavin Newsom has declared emergencies in a string of counties over the recent weeks, with the Biden administration also vowing continued federal support.
Meanwhile, a clipper system moving east through the lower Great Lakes was expected to bring light to moderate snowfall across the Great Lakes before reaching New England on Monday.
“Farther south, a wavy front is forecast to bring some severe thunderstorms across the Southeast through tonight,” the weather service said.
“This wave is forecast to interact with the clipper system moving across the Great Lakes and intensify rapidly into a potent nor’easter off the New England coast on Tuesday, bringing heavy wet snow inland and high winds with rain/snow near the coast.”
Heavy snow rates of up to 2 inches per hour are possible, while strong winds from the nor’easter could make travel “dangerous to near impossible,” the weather service warned. The severe weather conditions could also lead to outages and tree damage, it said.
Winds will also crank up, with wind gusts of 50 to 60 mph likely, especially right along the coast. This could result in blizzard conditions in areas where snow is falling.
Higher elevation areas across the interior Northeast could see more than 12 inches of snow, it said. It further warned that some areas, including the Catskills in New York, the Berkshires in western Massachusetts, and the southern Green Mountains in Vermont, could see localized higher snowfall amounts.
“Widespread minor coastal flooding may be possible Monday night through Wednesday as the low pressure deepens off the coast of New England with high winds most likely near Cape Cod later on Tuesday,” the weather service said.
On Wednesday, the system will move away from the coast, with morning snow lingering along coastal New England. Winds will stay strong all day in much of the Northeast.