Central United States Snowfall: Variability, Trends, and Large-scale Forcings

To adequately plan for and manage snow-based resources and efforts in a warming global climate, a firm understanding of the physical conditions that give rise to snowfall events, and how those conditions are responding to global climate change, is needed. This research evaluates the spatiotemporal variability, trends, and large-scale forcing mechanisms of snowfall frequency, timing, and intensity within the central United States over the last 73 years. Results indicate seasonal snowfall has broadly increased in within the northern Great Plains and decreased in the central Great Plains, including large decreases in March snowfall suggesting a shift in the snowfall season with time. Ten unique synoptic-scale systems contribute to snowfall across the region, where each generates snowfall in distinct sub-regions and with distinct seasonality. While many of the snowfall synoptic-scale systems are associated with snowbands and wraparound precipitation from mid-latitude cyclones, some 20% of snowfall in the western sub-regions is associated with easterly flow and thus topographically-enhancing snowfall receipts. The frequencies of multiple snowfall producing synoptic-scale systems are significantly correlated to large-scale modes of atmospheric and oceanic variability, including the North Atlantic Oscillation, the Pacific/North American pattern, and the El Nino Southern Oscillation, such that systems are more/less frequent during certain phases or combinations of phases of these teleconnection indices. Further, results suggest that many of the synoptic-scale systems exhibit linear trends in their inherent meteorological conditions that in turn influence snowfall frequency and intensity across the region with time. Such findings can provide valuable context to inform snowfall-related policy and management strategies.