Over 22 million Americans in Southern California are under a flood watch as a West Coast storm could slam burn scar areas, bringing potential mudslides and debris flows.

If rain falls as forecast, this storm could result in downtown Los Angeles seeing its wettest November since 1985. Heavy rain brings the possibility of damaging flooding and landslides.

Geomagnetic storms occur when charged particles from the sun collide with Earth’s atmosphere, creating auroras.

A Pacific storm could help California crews battle the dangerous Pack Fire in Mono County, but it could also wreak havoc on fire-charred communities further south.

Increased solar activity causes auroras that dance around Earth’s poles, known as the northern lights, or aurora borealis, and southern lights, or aurora australis. When the energized particles from coronal mass ejections reach Earth’s magnetic field, they interact with gases in the atmosphere to create different colored lights in the sky.

Evacuation warnings are in effect from 6 p.m. Thursday through 11 a.m. Sunday in areas near recent burn scars, due to the risk of mud and debris flows.

The loud sound that came with sheets of rain and fierce wind of an atmospheric river storm that whipped through the Bay Area on Thursday and dumped more than five inches of precipitation in some places and more than a half-inch elsewhere quieted Friday morning.

The storm dropped more than an inch of rain across the capital region and more impressive totals in the foothills.

For the West Slope Northern Sierra Nevada, including Blue Canyon, a winter weather advisory is also in effect to 10 a.m. Friday. Snow totals are expected to reach three to six inches south of Highway 50, with 12 to 18 inches at the highest peaks. Gusty winds up to 50 mph are also expected.

Cheltenham's meeting on Saturday has passed an inspection after heavy rain from Storm Claudia. The seven-race card features the Paddy Power Gold Cup (14:20 GMT), with the going described as heavy, soft in places. Racing went ahead on Friday, the opening day of the three-day meeting, but 35mm of rain fell.