A Climatology of Short-wave Troughs in the Great Lakes Region and their Interaction with Shore-Parallel Lake-Effect Snowstorms off of Lake Ontario

Lake-effect snowstorms can produce prolific snowfall amounts near the shores of Lake Ontario while presenting a hazard to public safety. Shore-parallel lake-effect snow bands are 20–50 kilometers wide and can extend inland for over 200 kilometers. While lake-effect snow is primarily a lower tropospheric event, middle and upper tropospheric features can have an impact on the evolution of lake-effect snow. Cyclonic vorticity advection ahead of a short-wave trough can deepen the lake boundary layer and cause inversion heights to rise. This presentation will provide a detailed description of an eight-year (2007–2015) cool season (October–March) climatology of 500-hPa short-wave troughs passages through the Great Lakes region. Further, this climatology will be utilized along with radar data analyze the change in Lake Ontario shore-parallel band orientation, latitude, intensity, and inland extent before and after short-wave trough passage.

The eight-year climatology reveals 696 short-wave troughs that passed through the Great Lakes region. These troughs most typically approach the Great Lakes region from the west or round the base of a long-wave trough and remain in the region for about 24 hours. Of these 696 troughs, 32 crossed a Lake Ontario shore-parallel lake-effect snow band that existed for at least 3 hours before and after its passage. As a short-wave trough axis approaches a preexisting snow band, there is a tendency for clockwise band rotation, a southward drift, intensification, and an increase in inland extent. After the short-wave trough axis passes the lake-effect band, there is less consistency in how the band character changes. These results indicate that 500-hPa short-wave troughs have a more predictable impact on lake-effect snow as they approach the storm than after they depart the Lake Ontario region. While changes to lake-effect snow bands may sometimes be subtle with the passage of a short-wave trough, they are still notable given that only minor changes to lake-effect snow bands can potentially cause substantial forecast errors for these high-impact storms.