A “pretty epic” amount of snow has fallen on California this year, but an atmospheric river bringing heavy rain from the Pacific is threatening to set off major flooding. “We’re going to see rain on top of snow, and for elevations of say 2,000 feet to about 4,000 feet, a lot of that snow is going to melt,” Carlos Molina, a meteorologist with the National Weather Service, told the LA Times. “We’re going to basically lose a lot of the snow that fell from the previous storms. We’re looking at potential for flooding.”

Big Bear City was buried under 80 inches (2.03 m/1 Scottie Pippen) of snow in just seven days and a National Guard unit accustomed to fighting wildfires was issued shovels to help residents simply get food and supplies to residents trapped in their homes. The already-dangerous flood risks of rain on top of snow are exacerbated by the Caldor and DIxie Fires, which left vast burn scars that now increase the potential for debris flows and substantial runoff into the Sacramento and San Joaquin watersheds.

“We haven’t had a big, warm atmospheric river atop a major snowpack in these regions, really, since we had these big wildfires,” UCLA climate scientist Daniel Swain told reporters. “We might be doing some science experiments in real time over the coming couple of weeks.” (Atmospheric river/flooding threat: LA Times $, CAL Matters, The Hill; Snow: AP, Washington Post $; “Pretty epic”: E&E $; Climate Signals background: Extreme precipitation increase; Wildfires)