Projected Changes in Interannual Variability of Peak Snowpack Amount and Timing in the Western United States

Abstract Interannual variability of mountain snowpack has important consequences for ecological and socioeconomic systems, yet changes in variability have not been widely examined under future climates. Physically based snowpack simulations for historical (1970–1999) and high‐emission scenario (RCP 8.5) mid‐21st century (2050–2079) periods were used to assess changes in the variability of annual maximum snow water equivalent (SWE max ) and SWE max timing across the western United States. Models show robust declines in the interannual variability of SWE max in regions where precipitation is projected to increasingly fall as rain. The average frequency of consecutive snow drought years (SWE max < historical 25th percentile) is projected to increase from 6.6% to 42.2% of years. Models also project increases in the variability of SWE max timing, suggesting reduced reliability of when SWE max occurs. Differences in physiography and regional climate create distinct spatial patterns of change in snowpack variability that will require adaptive strategies for environmental resource management.