Rising 'snow-eater' heat waves accelerate melt and flood risk in the West

A new study shows that short, intense heat waves that melt snow—dubbed “snow-eater” events—are becoming more common across the western United States, boosting flood danger.

Scientists used a novel detection method on historic air-temperature data and a snow-melt model to quantify “snow-eater” heat waves—brief periods of rain-on-snow followed by unusually high temperatures that trigger rapid melt. Their analysis, published in Science Advances, indicates these events typically last three to five days, appear three to five times each decade, and have doubled snow-melt rates since the 1850s. The researchers noted that seven of eleven recorded spring super floods coincided with such heat waves, and that both the area affected and the frequency have risen while the duration has shortened, shifting earlier in the melt season.

Since the mid-1990s, the western United States has seen nearly twice as many of these heat waves, amplifying flood risk. The authors propose that the detection technique could improve municipal water-resource planning and sub-seasonal to seasonal forecasting. They call for further investigation given the potential impact on water supplies and natural hazards.