Trends in Snowfall versus Rainfall in the Western United States

Abstract The water resources of the western United States depend heavily on snowpack to store part of the wintertime precipitation into the drier summer months. A well-documented shift toward earlier runoff in recent decades has been attributed to 1) more precipitation falling as rain instead of snow and 2) earlier snowmelt. The present study addresses the former, documenting a regional trend toward smaller ratios of winter-total snowfall water equivalent (SFE) to winter-total precipitation (P) during the period 1949–2004. The trends toward reduced SFE are a response to warming across the region, with the most significant reductions occurring where winter wet-day minimum temperatures, averaged over the study…

• UD
  U.S. Department of Energy
• CE
  California Energy Commission
• NO
  National Oceanic and Atmospheric Administration
• UG
  U.S. Geological Survey