Regional Flooding
California Atmospheric River Guide: Flooding, Snow Levels, Mudslides, and Reservoirs
How atmospheric rivers affect California, including heavy rain, Sierra snow, snow levels, burn scars, mudslides, and reservoirs.
Quick answer: California atmospheric rivers can deliver beneficial water supply and dangerous flooding, depending on moisture, storm track, duration, and snow level.
Rain and snow
Low snow levels can build Sierra snowpack, while high snow levels can increase runoff and flood risk.
Warm storms can melt existing snow.
Burn scars
Recent wildfire burn scars can respond quickly with debris flows during intense rain.
Evacuation warnings should be taken seriously.
Water balance
Atmospheric rivers help reservoirs and snowpack but can also overwhelm rivers and roads.
Both benefits and hazards can happen in the same season.