Temporal trends in snowfall contribution induced by lake-effect synoptic types

Using a synoptic classification technique and gridded snow dataset, snowfall was evaluated in the eastern Great Lakes region from 1950-2009 during atmospheric conditions suitable for the development of lake-effect snow. Specific emphases were placed on detailing the long-term changes to snowfall magnitude and frequency, and quantifying changes in the contribution of total snowfall from lake-effect synoptic types. For Lakes Erie and Ontario, snowfall from lake-effect synoptic types represented approximately 48% of total snowfall, and 42% of snowfall days are synoptically lake-effect in nature. Over time, the percentage of total early-season snowfall from lake-effect synoptic types significantly increased downwind of the Lakes, by approximately 0.4% yr-1, corresponding to an increase from approximately 40% lake-effect in the 1950s, to over 60% in the 2000s. This was due, in part, to changes in the frequency of snowfall-producing synoptic types, decreases in the percentage of precipitation falling as snow during non-lake-effect events, and increases in the magnitude of snowfall per lake-effect event. Changes in the proportion of total snowfall from lake-effect processes carries implications to water resources due to differences in snow-water-equivalent between lake-effect snow and snowfall from other mechanisms, such as mid-latitude cyclones.