LOS ANGELES _ The first in a parade of three winter storms that brought thunder and lightning to California's Central Coast overnight began to hammer Los Angeles County early Thursday, sending mud streaming onto Pacific Coast Highway and prompting the closure of the roadway between Ventura and L.A. counties.
The rain also sent gushing mud down a hillside near Deer Creek Road and Pacific Coast Highway.
No evacuations have been ordered in the areas of the county recently scarred by the Woolsey fire. However, Riverside County officials have issued mandatory evacuation orders for residents affected by the Holy fire and said those in the burn zone from last year's Cranston fire should also prepare to leave in the event of heavy rain. The situation is becoming common for those areas where residents have been told to evacuate during past storms.
The storm had already dumped a significant amount of rain on Santa Barbara County by early Thursday. Rainfall rates of up to half an inch per hour were measured in some areas, prompting the National Weather Service to issue flood advisories for Santa Barbara and Ventura counties. Forecasters said gusty winds and dime-size hail could potentially develop in parts of Santa Barbara County.
The National Weather Service also issued a flash-flood watch for all the most recent burn scars in Los Angeles, Riverside and Orange counties through Thursday afternoon.
While the rainfall rates weren't heavy enough to cause concerns about mudslides for the area damaged by the Thomas fire in 2017, there could be potential for debris flows and flooding in other areas if the storm maintains its strength, said Keily Delerme, a meteorologist with the National Weather Service in Oxnard.
"It's been raining pretty much all night here and the storm doesn't seem to be weakening," she said.
The slow-moving system could drop more than an inch of rain throughout the day in L.A. County, although predictions call for roughly half an inch of precipitation.
Lightning along the coast prompted officials to close Zuma Beach as the storm began to dump rain on Malibu.
"Other beaches are being monitored and may be closed depending on storm activity and direction," the city said in an announcement. "Residents and visitors are urged to stay away from all beaches until the series of storms forecast for Thursday through Monday have passed through Malibu."
The lightning also persuaded officials in Santa Monica to evacuate beaches and the pier. L.A. County lifeguards were continuing to monitor beaches and urged people to seek shelter off the beaches if lightning strikes.
The rain could cause other hazards as well. Authorities in Palmdale have warned the public to avoid city streetlight poles during the storms because of wiring problems that could deliver an electric shock to people when the lights are on in the rain.
Southern California will have a short break from wet weather Friday before a stronger system moves into the region that night. That atmospheric river-fueled storm has the potential to bring gusty southeast winds up to 60 mph and dump 1 to 3 inches of rain through Saturday in Los Angeles County. It also may bring snow to higher elevations.
Atmospheric rivers are fairly long, narrow regions in the atmosphere _ similar to rivers in the sky _ that can hold as much water as the mouth of the Mississippi River.
"The impacts we're looking at are downed trees, travel delays and possible shallow debris flows," said Lisa Phillips, a meteorologist intern with the National Weather Service in Oxnard. "The second storm is the one where you want to stay home."
While the heavy rain they produce can cause flooding, weather experts say atmospheric rivers aren't all bad. They also can help replenish dwindling water reserves and contribute beneficial increases in the state's snowpack.
A much weaker third storm arriving Sunday will bring scattered showers that could linger through Monday, forecasters said.
