Abstract ID: 3.9088 | Reviewing | Talk/Oral | TBA | TBA

Abrupt snowmelt, whether through rain-on-snow or snow-heatwave interactions (snow-eaters), can increase the risk of midwinter and spring flooding, accelerate the onset of snow drought during late spring and early summer, and alter water availability later in the year. Snow-eater heatwaves have been less studied than rain-on-snow events, yet have the potential to increase in area, duration, frequency, and/or intensity in a rapidly changing climate. Using the Twentieth Century Reanalysis Version 3 (20Cv3) we develop an approach to identify snow-eater heatwaves, estimate their melt potential, and explore how their characteristics (e.g., area, intensity, duration, and frequency) have changed over the last two centuries (1806-2015). TempestExtremesv2 is used to track snow-eater heatwave events, and an operational snowmelt model (SNOW-17) is used to estimate their heatwave melt potential. Additionally, we developed a few experimental forms of SNOW-17 that add non-linear snowmelt during heatwave events (which is currently not incorporated in SNOW-17). We optimize our approach over western North America using a few notable snow-eater heatwave events in recent history (e.g., 1983, 2002, and 2013) and compare the SNOW-17 snowmelt estimates to in-situ measurement networks (SNOTEL sites) over an overlapping period of record to 20Cv3 (1980-2015). We then utilize the best-performing SNOW-17 models to perform trend analyses of snow-eater heatwave characteristics from 1806-2015. Results indicate that heatwave definition is essential to inferences about the effects of heatwaves on snowmelt and that snow-eater heatwaves have made large contributions to historical and highly consequential melt events, such as in 1983.