Rachel Carlsen was outside her son’s school in Ladera Ranch the morning of Tuesday, March 20 when she noticed something strange in the sky.

“It looked like a tear in the cloud,” Carlsen, 35, said. “I didn’t know what I was looking at, but I knew I’d never seen anything like it before.”

She snapped a photo with her iPhone and later Googled the phrase “hole in cloud.” It turned out that she’d captured a rare instance of a fallstreak hole, a phenomenon where a large circular gap appears in a high-altitude cloud.

Also known as a “hole-punch cloud,” this rare formation appears when water droplets in the cloud cool to temperatures below freezing — but don’t freeze over. If there’s a disturbance to the cloud — such as a plane — it triggers the rapid formation of ice crystals. The crystals fall out of the cloud in streaks, leaving behind an expanding gap.

“It’s not something you see in Orange County every day,” Carlsen said.

The winter storm approaching Southern California this week is said to be opening up an “atmospheric river” of subtropical rain clouds ahead of a cold front, according to forecasts. Rain is expected to fall starting Tuesday afternoon.