Saturday, 13 January 2007
A climatological study of Lake Champlain lake-effect snow band events
A number of recent studies have indicated that lake-effect snows can occur in association with lakes of significantly smaller size than the Great Lakes. As an example, Lake Champlain lake-effect storms can generate snowfalls over localized regions which are comparable to large-scale winter storms and on rare occasions produce snow squalls with visibilities less than ¼-mile and up to 33-cm (13 inches) of snow in a 12-hour period. To establish a more complete picture of the lake-effect snows in the vicinity of Lake Champlain, a climatological study has been undertaken to determine the frequency and environmental conditions favorable for these events. WSR-88D radar data collect near Burlington, VT was used to identify 67 lake-effect events for the winters (October – March) of 1997 through 2005. Lake Champlain lake-effect events were found to develop as (a) well-defined, isolated snow bands over and downwind of the lake, independent of larger-scale weather systems, or (b) a quasi-stationary mesoscale snow band over the lake embedded within widespread regional snowfall from a synoptic weather system.
A unique finding from this investigation shows that Lake Champlain lake-effect events occur under both northerly and southerly wind regimes. Approximately 25% of the 48 events having an isolated snow band over Lake Champlain developed within a southerly wind regime. When compared to Lake Champlain events with northerly winds, southerly wind events were found to occur with lower wind speeds, colder air temperatures, and a larger contribution of land breezes to the low-level convergence. An intrusion of an arctic airmass was frequently observed during southerly flow events, extending from north of the Lake Champlain valley southward along the Appalachian Mountains. Additional details describing the environments favorable for the development of Lake Champlain lake-effect snow band events will be presented at the conference.