An atmospheric river storm looming in California will dump more rain and snow this week, raising fresh concerns about additional flooding and snowmelt in the already soggy state.
The storm, which originated near Hawaii, is expected to intensify Monday through Wednesday. It will create “significant flooding impacts below 5,000 feet along much of the California coast and Central Valley and over the southern Sierra Nevada foothills,” the National Weather Service said.
Once again, rivers, creeks and creeks in several areas are forecast to overflow their banks, including some, such as the Cosumnes, Salinas and Russian rivers, which are still in flood from a similar storm last week.
Last week’s storm prompted dozens of water rescues and saw thousands of Californians under evacuation orders. On Friday night, heavy rains breached a levee on the Pajaro River, flooding an entire town and trapping dozens of residents, many of them migrant farm workers.
Heavy rain remains a major concern with the incoming system, and the weather service has issued more than 30 flood watches and warnings in the state, with the strongest impacts expected as the system moves from the central coast toward the southern Sierra foothills.
“Things are very saturated; the ground is ready to move,” said Eleanor Dhuyvetter, a meteorologist with the San Franscico Bay Area weather service. She noted that the region has already seen urban flooding, rock slides and debris flows, and forecasters are “definitely looking at some flood impacts for the larger amounts coming Tuesday.”
The storm began as convection near Hawaii before building into a strong low-pressure system, Dhuyvetter said, and is expected to link up with some upper-level energy on Monday.
“We have been watching it and it has definitely intensified in the last 24 hours. Once it meets that higher level energy, it will move quickly and slam into the shoreline, just off the Bay Area,” he said.
The storm is expected to be strongest in the Bay Area overnight Monday and into Tuesday, while the Central Valley and areas further inland should see the worst of it Tuesday afternoon into Wednesday, according to Brian Ochs, a meteorologist with the weather service in Hanford.
Inland areas of particular concern are Merced County near Bear Creek, as well as parts of Mariposa, Fresno, Madera and Tulare counties, which will see the most rain, Ochs said. “Kern won’t be as much, but there could still be some local flooding impacts.”
Up to 6 inches of rain could fall in mountainous areas up to 7,000 feet, with up to 3 inches possible in the foothills and 1.5 inches in the San Joaquin Valley, Ochs said.
Plenty of wet snow is also expected to fall at higher elevations, particularly in the Sierra Nevada, which will “further complicate snow load impacts and issues,” the weather service said. The state has already seen a number of roof collapses due to heavy snowfall.
Tioga Pass and Mt. Whitney could see up to 48 inches of fresh powder, with up to 24 inches of snow at Mammoth Lakes.
Widespread rain is also expected in southern California, including up to 7 inches in the mountains of southeastern Santa Barbara County and western Ventura County, with the storm’s peak expected to arrive Tuesday. The Ventura River may be approaching flood stage, with smaller creeks and creeks expected to fill, said Mike Wofford, a meteorologist with the weather service’s Oxnard office.
“In Santa Barbara County, there are a ton of streams, the mountains are right there in your backyard, so all that water just flows,” Wofford said. “There are tons of them, and they are going to fill up, and some of them are going to spill onto the road, so there will probably be some problems on the 101.”
Highway closures, landslides and debris flows are likely, he said. In the greater Los Angeles area, up to 3 inches of rain is possible, along with clogged storm drains and flooded intersections, she said.
The storm is “a little shorter in duration than the last one, but it’s more intense: we’re going to end up with more rain in Los Angeles than the last one,” he added.
The California Governor’s Office of Emergency Services said Monday it was Positioning of resources to combat floods. and responding to potential emergencies in nearly 20 counties across the state, including swift water rescue teams in Fresno, Inyo, Sacramento, Monterey, Tulare, Los Angeles and San Luis Obispo counties.
The storm comes on the heels of one of California’s wettest and snowiest winters on record. Nearly two dozen people died during a series of nine consecutive atmospheric rivers in January, and at least 13 people were found dead after heavy snow accumulated in the San Bernardino Mountains in late February and early March.
Statewide snowpack Monday was 212% of normal for the date, while Oroville and Shasta, the state’s two largest reservoirs, were 76% and 63% full, respectively.
Forecasters feared that wet soils, swollen streams and low-lying snowpack would only exacerbate problems for hours and days to come.
“With so much water already, more moisture will continue to cause impacts,” Dhuyvetter said.
