Projected Changes in Snowfall Extremes and Interannual Snowfall Variability in the Western United States

Projected warming and more variable precipitation will impact snowfall accumulation and melt, with implications for water availability and management in snow-dominated regions. Projected changes in extreme snowfall events, which constitute 20-38% of annual snowfall water equivalent (SFE) in the western U.S., are confounded by projections of more extreme precipitation and the differential temperature sensitivities of snowfall events. Data from 20 global climate models downscaled and bias corrected to western U.S. Snowpack Telemetry stations are used to assess projected changes in extreme snowfall events and annual SFE. Annual SFE is projected to decrease at all stations. In the coldest regions, changes in the distribution of snowfall and precipitation events are similar, with substantial increases in the most extreme events and smaller changes in small and moderate events. In warmer regions, reductions are projected for all snowfall events, however large events will be far more resilient than small and moderate events due to differential temperature sensitivities and changes in precipitation. Variability in annual SFE is projected to increase, particularly in warmer regions, due to fewer snowfall days and the increasing importance of heavy snowfall events. In the coming century, water management will be challenged by reduced and significantly more variable snowpack.