Higher prevalence of rising climate-driven snowmelt potential of rain-on-snow events in the Eastern Continental US

Abstract Rain-on-snow (ROS) events have significant hydro-geomorphological consequences. While these events have been widely studied, their meteorological capacity to thermodynamically alter or melt snow when unconstrained by snow amount, hereafter referred to as snowmelt potential (SMP), remains poorly understood, particularly with respect to its long-term trends. Here, we evaluate climate-driven trends in SMP, estimated as the snowmelt-inducing total surface energy flux transferred during ROS events assuming unlimited snow availability, across 8,991 sites in snow-affected regions of the continental United States over a 39-year period (1981-2019). Overall, SMP exhibits an increasing trend at ~63% of the sites with the proportion of sites showing positive trends rising from 54.4% in the Western region, to 64.6% in the Central region, and 78.4% in the Northeastern United States. The spatial pattern of SMP trends remains robust to uncertainties arising from omitted radiative fluxes and dampened wind-speed trends. High-energy ROS events are found increasing at majority of stations, with the positive trends becoming more widespread as the energy threshold rises. SMP trends are primarily governed by changes in net radiation and sensible heat flux, modulated in large part by trends of event air temperature and wind speed. Findings suggest growing meteorological hazard potential from ROS events, especially at high-SMP sites, highlighting increased risk with continued climate warming.