Snow-eater heatwaves of the western United States

Abrupt snowmelt, triggered by rain-on-snow events or ``snow-eater heatwaves'', can cause flooding, accelerate snow drought, and impact water availability. Yet the characteristics (e.g., area, duration, and frequency), impacts, and trends of snow-eater heatwaves have received relatively little attention. To address this gap, we developed a method to identify snow-eater heatwaves and estimate their melt potential using Twentieth Century Reanalysis Version 3 air temperature data, the TempestExtremes algorithm, and an operational snowmelt model (SNOW-17) across 1850–2015. Melt season snow-eater heatwaves typically last 3–5 days, with 3–5 events, doubling snowmelt rates. Seven of 11 spring superfloods can be linked with snow-eater heatwaves. Since the 1850s, snow-eater heatwaves have increased in area and frequency, decreased in duration, and shifted earlier in the melt season. Incorporating snow-eater heatwave impacts into SNOW-17 improves extreme snowmelt estimates, providing additional tools to support water management.