LAUSR

Atmospheric rivers (ARs) are regions of high water vapor transport in the lower atmosphere. When these air masses encounter mountain ranges, they can produce significantly enhanced orographic precipitation. AR events may substantially influence seasonal mountain snow, an important ecologic and economic resource for Washington, Oregon, and California. To better understand how ARs affect the montane snowpack of these U.S. West Coast states, we used 33 years of Snow Telemetry and Topography Weather data to examine AR and non‐AR storm day temperatures and impacts on snow water equivalent (SWE). We found mean daily minimum temperatures of AR storm days to be 1 to 4 °C warmer and mean daily increases in SWE to be 23% to 57% higher than non‐AR storm days. AR storm days have contributed an average of 23% of effective snowfall to seasonal SWE in the California Sierra Nevada and 34% of effective snowfall to seasonal SWE in the Washington and Oregon Cascades.