Flooding, mudslides possible as California snow melts amid another round of atmospheric rivers


(NEW YORK) — Some of the regions in California buried under several feet of snow are now bracing for rapid melting due to forecasts of higher temperatures and heavy rain.

Another round of atmospheric rivers will be slamming much of California with tropical moisture over the coming days, washing away the snowpack that has accumulated in recent weeks forecasts show.

Up to 8 inches of rain is expected to fall on top of the piles of snow in lower elevations, which could cause flash flooding and present the risk for mudslides and rockslides with debris flow as streams as rivers rise quickly and saturated slopes are unable to hold in the extra moisture.

Those risks will be compounded by the flooding rain that moves in as the storm system approaches, Brian Ochs, meteorologist for the National Weather Service in Hanford, California, told ABC News.

If possible, please avoid heavy snow buildup on roofs. Heavy snow on roofs can damage them and potentially cause them to collapse. Moderate to heavy rain is expected late Thursday into the weekend, and snow on roofs can absorb the rain and become even heavier. #CAwx pic.twitter.com/3squOdOrk2

— NWS Sacramento (@NWSSacramento) March 8, 2023

Elevations higher than 9,000 in the Sierra Nevada mountains will experience even more snow, leading to concern that additional snow accumulations will cause rooftops to collapse in the region, Ochs said. In the lower elevations that receive rain, the moisture could be absorbed by the snowpack, increasing the risk for structural damage, the National Weather Service warned.

“That could cause some damage if they don’t get the snow off the roofs,” he said.

High avalanche danger is expected for the Sierras and mountains in Southern California as well, forecasts show.

The bulk of the rain is expected to begin falling Thursday evening into Friday morning, Ochs said. Flood, winter storm and high wind watches have been issued all over the state.

The San Joaquin Valley could reach flood stage by Friday as creeks and rivers near Merced County and Yosemite National Park overflow, Ochs said. Flood watches have been issues for places like Redding, Bakersfield and east of the state, in Reno, Nevada.

Flooding is even possible in the San Francisco Bay, where more than 3 inches of rain could fall in a short amount of time. Heavy rain will begin reaching Los Angeles on Thursday night into Friday.

Parts of Southern California are already experiencing flooding. Video taken Tuesday in Sunland, a town about 20 miles north of Los Angeles, shows roadways inundated with rushing floodwaters as the snow in the foothills begins to thaw.

Anyone living near creeks and rivers should create an evacuation plan due to the flooding risk, Ochs said.

“Keep up with what the sheriffs are asking the residents to do,” he said. “Heed their warning.”

The messy weather will continue past the weekend, with another atmospheric river system already on the horizon past the weekend and into Wednesday, Ochs said.

Additional systems could be on the heels of that one later next week, Ochs said, citing National Oceanic and Atmospheric Administration’s Climate Prediction Center.

“We are in a pretty high risk of at least being in above average precipitation next week,” Ochs said.

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