On the origin of recent changes in western North American snowpack

Monthly snow water equivalent station observations and gridded temperature data is used to assess changes in western North American mountain snowpack from 1930 to present. Trends in monthly snow water equivalent, inter-month changes in snow water equivalent, snow centroid date, and temperature are examined to explore intraseasonal changes in snowpack. A few small regions exhibit positive snowpack trends as a result of early season enhanced accumulation. However, western North America predominantly experiences reduced snowpack values and warming, with enhanced signals during the months of March and April. The snow centroid date is used as a proxy for the onset of snowmelt and is shown to shift earlier in the season as a result of late spring warming over the time period. Given predictions of future warming, a further advancement in the onset of snowmelt should be expected in the coming decades.