An abnormal change in the weather is bringing the possibility of showers and thunderstorms to Southern California, raising some concerns about flooding as temperatures also fall well below average for mid-September.
For much of the Los Angeles area, the system is expected to bring only light rain or drizzle on Thursday and Friday, but there is a chance for pockets of thunderstorms to form that could bring heavier rainfall.
The greatest chance for thunderstorms is in the mountains, including along the Interstate 5 corridor and across the San Gabriel, according to Bryan Lewis, a meteorologist with the National Weather Service in Oxnard.
“We’re looking at less than a tenth of an inch, maybe up to a quarter of an inch in the mountains,” Lewis said. “It could be more if a big thunderstorm develops in a given area.”
He called the weather pattern “somewhat abnormal” for this time of year, given that September is typically one of the driest and warmest months in Southern California.
Lewis said the amount of rainfall expected is “definitely above average for what September typically brings, and we’re also well below average in terms of temperatures.”
Much of Ventura and San Luis Obispo counties, as well as western Kern County and parts of Santa Barbara County, are under a flood watch Thursday. People living near hurricane and Apache burn areas are at particular risk, according to the National Weather Service, and should prepare for the possibility of debris flows and flooding.
Thunderstorms in these areas of southwestern California are “capable of producing heavy rainfall… [R]“Flooding events of one-half inch every 30 minutes and one inch per hour will be possible,” the National Weather Service wrote in its flood alert.
According to local officials, the Apache Fire in late July burned about 1,500 acres near Ojai in the Los Padres National Forest. The Hurricane Fire reached about 10,000 acres in mid-July, burning primarily in the Carrizo Plain National Monument in San Luis Obispo County, according to the California Department of Forestry and Fire Protection.
National Weather Service forecasters also warned that residents near the Lake Fire burn zone in the mountains of Santa Barbara County should be prepared for heavy rain, although that area was not yet part of the flood watch. There is a 20% chance that thunderstorms could also move into that area, causing flash flooding and debris flows, the weather service warned.
The Lake Fire burned nearly 40,000 acres this July, starting near Zaca Lake.
Meanwhile, parts of the Sierra Nevada are also expected to feel the effects of the wet, cold pattern, and a winter weather advisory has been issued for some of the highest peaks in Yosemite, Kings Canyon and Sequoia national parks, as well as Mammoth Lakes. Elevations above 9,000 feet are expected to receive between 2 and 5 inches of snow on Thursday, according to the advisory.
