The Contribution of Upper-Level Flow Regimes to Seasonal Snowfall Totals in Upstate New York

Central New York is well-known for its winter climate, a climate characterized by some of the highest snowfall totals in the United States east of the Rocky Mountains. However, the region is particularly relevant due to its location at the intersection of the eastern Great Lakes and Northeast United States. Its location regularly results in snowfall throughout the winter from a variety of storms including lake-effect, Nor'easters, Colorado lows, and Alberta clippers. As the climate changes, it is expected that there will be a shift in the frequency of these snowstorms, with an increase in snowfall from lake-effect storms and a decrease in snowfall from non-lake-effect storms. This has the potential for drastic consequences as snow, although it can hamper human activity whether recreational or economic, plays a significant and critical role in the region's surface energy balance, and in particular in its hydrological regime. Therefore, the main objective of this study is to classify, track, and characterize individual snowstorms from 1985/86 – 2014/15 to determine how their frequency, magnitude, and seasonal snowfall percent contribution has changed over time. In addition, individual snowstorms are examined to determine commonalities in snowfall totals, the distribution of the snowfall, and the snow-water equivalency of the snow for storms with a similar area of cyclogenesis and track.

Individual snowstorms are identified using COOP data for twelve Central New York counties, and are grouped into light (3 – 10.1 cm), moderate (10.2 – 25.4 cm), and heavy (≥ 25.4 cm) events. Events are then divided into lake-effect and non-lake-effect storms using satellite imagery; with non-lake-effect events further grouped based on their storm type (east coast storms, Colorado lows, and Alberta clippers) using NCEP/NCAR reanalysis data. The track of each snowstorm up to 72 hours prior to the storm entering Central New York is calculated using NOAA's HYSPLIT model, and similarities in snowfall characteristics are analyzed using ArcGIS. The percent contribution of each snowstorm type and temporal changes in the frequency and magnitude of each storm type are calculated. Past research and preliminary results suggest that the frequency of snowstorms and the percent contribution of lake-effect snow east of Lake Ontario have increased over time, with a less pronounced increase in less typical lake-effect zones. Since the dominant snowstorm of an area exhibits strong regional variations throughout the United States, this study will provide a better understanding of the dynamics of storms tracks and their impact on snowfall and water resources for the eastern Great Lakes. The methodologies and results from this study can then be used directly by weather forecasters and hydrologists to improve snowfall and river flooding forecasting, which are essential to reduce the risk of life threatening situations encountered during snowstorms.