An atmospheric river storm battering California will drop more rain and snow this week, raising new concerns about additional flooding and snowmelt in the already soaked state.
The storm, which originated near Hawaii, is expected to intensify Monday through Wednesday. This will create “extensive flood impacts below 5,000 feet elevation over much of the California Coast and Central Valley and the southern foothills of the Sierra Nevadas,” the National Weather Service said.
Rivers, streams and streams in several regions are expected to overflow again – including some, such as the Cosumnes, Salinas and Russian rivers, which are still swollen from a similar storm last week.
“Previous conditions are extremely wet and watersheds are primed, so it won’t take much rainfall to cause immediate runoff and surges in rivers and streams, and flooding in urban areas,” the climatologist said. of UCLA, Daniel Swain, at a conference. Monday briefing.
Last week’s storm triggered dozens of water rescues and saw thousands of Californians under evacuation orders. On Friday evening, heavy rain broke through a dyke on the Pajaro River, flooding an entire town and trapping dozens of residents, many of them migrant farm workers.
Along the nearby Salinas River, evacuation orders and warnings remained in effect for more than 10,000 people, with Monterey County officials warning of “likely flooding of roads between the Monterey Peninsula and the rest of the county” due to the impending storm.
Governor Gavin Newsom expanded his storm-related state of emergency to include Calaveras, Del Norte, Glenn, Kings, San Benito and San Joaquin counties, bringing the total number of counties under the declaration to 40.
President Biden issued an emergency declaration on Friday, authorizing the Department of Homeland Security and the Federal Emergency Management Agency to support state and local responses to the series of storms.
Biden is closely monitoring heavy rains and flooding, including the breach of the Pajaro River levee, White House press secretary Karine Jean-Pierre told reporters on Air Force One on Monday. . Biden, who is heading to California for a two-day visit that includes stops in San Diego and Monterey Park, spoke with Newsom over the weekend, Jean-Pierre said.
Heavy rain remains a major concern with the incoming system, and the weather service has issued more than 40 flood watches and warnings, with the heaviest impacts expected as the system moves from the central coast into the southern foothills of the Sierra. Flood watches have also been issued in northern California, including parts of Del Norte, Humboldt and Trinity counties.
While the incoming storm’s total rainfall may not be greater than last week’s storm, the risk of flooding could be significantly higher due to more intense rainfall and already wet conditions, said Swain.
“We’ve just had all this rain, the rivers are already high, there’s still residual snowmelt – all of these things point to high flood risks with this event compared to the last,” he said. declared.
In addition to Monterey County, evacuation orders and warnings are also in effect in parts of Fresno, Merced and Tulare counties, among others, and more than 30 evacuation shelters are open across the state. An evacuation order will be in effect from 8 a.m. Tuesday for areas associated with the Alisal and Cave Fire burn scars in southern Santa Barbara County.
The San Francisco Bay Area has experienced urban flooding, landslides and debris flows before, said Weather Services meteorologist Eleanor Dhuyvetter.
“Things are very saturated; the ground is ready to move,” Dhuyvetter said, adding that forecasters are “certainly looking at some flood impacts for the heavier amounts that will arrive on Tuesday.”
The storm began with convection near Hawaii before developing into a powerful low pressure system, Dhuyvetter said, and is expected to link up with higher level energy on Monday.
“We’ve been watching it, and it’s definitely intensified over the last 24 hours. Once it encounters this higher level energy, it’s going to move quickly and crash into the coast there, just next to the Bay Area,” she said.
The storm is expected to be strongest in the Bay Area overnight Monday through Tuesday, while the Central Valley and areas further inland are expected to be worst affected Tuesday afternoon through Wednesday, a said Brian Ochs, meteorologist with the Hanford Weather Service.
Interior areas of particular concern are Merced County near Bear Creek as well as parts of Mariposa, Fresno, Madera and Tulare counties that will see the most rain, Ochs said. “Kern won’t be as significant, but there could still be some local flooding impacts.”
Up to 6 inches of rain could fall in mountainous areas reaching 7,000 feet, with up to 3 inches possible in the foothills and 1.5 inches in the San Joaquin Valley, Ochs said.
Heavy, wet snow is also expected to fall at higher elevations, particularly in the Sierra Nevada, which “will further aggravate impacts and snow load issues,” the weather service said. The state has already seen a wave 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 rainfall 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 on Tuesday. . The Ventura River could approach flood stage and smaller creeks and creeks are expected to fill, said Mike Wofford, meteorologist with the Oxnard Weather Services office.
“In Santa Barbara County, there’s a ton of streams — the mountains are right there in their backyard — and so all that water is just flowing,” Wofford said. “There’s tons of them, and they’re going to fill up, and some of them are spilling onto the freeway, so there’s probably going to be trouble on the 101.”
Highway closures, mudslides and debris flows are likely, he said. In the Los Angeles metro area, up to 3 inches of rain is possible, along with clogged storm drains and flooded intersections, he said.
The storm is “a bit shorter than the last one, but its intensity is higher – we’re going to end up with more rain in LA than we did with the last one,” he added.
The Governor’s Office of Emergency Services said Monday it is positioning resources to fight floods and respond to potential emergencies in nearly 20 counties across the state, including swiftwater rescue teams in Fresno, Inyo, Sacramento, Monterey, Tulare, Los Angeles and San Luis Obispo counties.
State water managers continue to lower dam levels to make room for inflows, including Lake Oroville, the state’s second-largest reservoir, which is at 76% full. ability. Discharges from its dam into the Feather River continued Monday at about 15,000 cubic feet per second, said Molly White, operations manager at the Department of Water Resources.
“We continue to closely monitor lake levels, weather and runoff forecasts,” White said, “and will make adjustments as needed to manage lake levels.”
The weather service warns that the system can also bring thunderstorms and strong winds, with high wind warnings in effect for several regions. Coastal areas from Cloverdale to Big Sur could see gusts of up to 70 mph, while the Sacramento Valley, San Joaquin Valley and surrounding areas could see gusts of up to 60 mph.
The storm comes just after one of the wettest and snowiest winters on record in California. Nearly two dozen people were killed during nine consecutive atmospheric rivers in January, and at least 13 people were found dead after heavy snowfall in the San Bernardino Mountains in late February and early March.
Statewide snowfall on Monday was 212% of normal for the date, while Lake Shasta — the state’s largest reservoir — was 63% full.
Although conditions are expected to clear in most areas soon after the storm, the relief will be short-lived, said state climatologist Mike Anderson. Another atmospheric river could arrive in California between March 19 and 22, with potentially another one to follow.
“We’re getting some clearance, which is good,” Anderson said. “But we’re not done yet.”
Times writers Courtney Subramanian, Susanne Rust and Ian James contributed to this report.