Snow-eater heat waves accelerate snowmelt in Western U.S

Scientists have identified a specific weather pattern termed ‘snow-eater’ heat waves, which are significantly accelerating snowpack depletion in the Western United States. According to a study published in Science Advances, these events are characterized by sustained temperatures that remain above freezing for three to five consecutive days, including through the night. This overnight warmth prevents the snowpack from refreezing, causing the entire layer to ‘ripen’ and melt much faster than usual.

Research indicates that during these heat waves, the rate of snowmelt can nearly double, jumping from a typical 9 millimeters of water per day to approximately 17 millimeters. This rapid melting poses serious risks to water resource management and has been linked to major spring flooding; seven of the eleven largest spring floods in the Western U.S. since 1950 occurred within five days of such an episode.

Climate data shows these phenomena are becoming more frequent and arriving earlier in the year. Since 1850, the area affected by these heat waves has expanded by approximately 102,000 square kilometers per century, and the first occurrence of the season is arriving about one month earlier per century compared to the mid-1800s.