A Proposal for Studying Rain-on-Snow Events: A Case Study from SNOTEL Data in the Southern Rocky Mountains, USA

Our climate is changing, especially in colder regions where snow dominates the hydrological cycle. Some areas have already crossed a threshold and are seeing more rain on the snowpack than previously. Such changes will alter the amount of water stored as snow as well as the timing of snowmelt, and thus the amount of water that will appear downstream and when the peak flows will occur. Here, a method is proposed to determine the occurrence and quantity of precipitation during rain-on-snow events, including the in-filling of missing snow depth data. The investigation focuses on three Snow Telemetry (SNOTEL) stations at different elevations in the Southern Rocky Mountains in the Western United States. The stations are located in the southern part of this mountain range that has been in drought for the past two decades. Almost 20 years of snow station data are analyzed to determine changes. Precipitation is decreasing, more so with elevation, and winter temperatures are increasing. The amount of rain-on-snow is decreasing.