Projecting Changes in Societally Impactful Northeastern U.S. Snowstorms

The northeastern United States is vulnerable to many impacts from snowfall-producing winter cyclones that are amplified by the proximity of population centers to storm tracks. Historically, climatic snowfall assessments have centered around seasonal means even though local impacts typically occur at scales of hours to days. To detect snowstorms at the event level, an objective algorithm is defined based on the Regional Snowfall Index. The metric collocates storm snowfall with population to produce statistics of snowstorms with societal impacts. When applied to the Community Earth System Model Large Ensemble, broad declines in snowstorm frequency are projected by the later 21st century. These decreases are primarily due to a warmer atmosphere less conducive to snowfall as the predominant precipitation type. However, reductions are less significant for major events, since more hostile thermodynamic environments are partially offset by increased precipitation associated with cyclones that dynamically drive high-impact snowstorms.