Relationships between synoptic weather type frequencies and snowfall trends in the lee of lakes Erie and Ontario

The relationship between synoptic weather type frequencies and snowfall trends in the lee of lakes Erie and Ontario is investigated. Large positive trends in monthly snowfall values are documented for the traditional snow belt regions for the period 1931 through 1990 for the month of January. The Temporal Synoptic Index (TSI) is used to identify synoptic patterns that are common to the eastern Great Lakes region during the snowfall season (November through March). The association between an individual synoptic pattern and snowfall is evaluated by consideration of basic meteorological principals. Results indicate that the positive snowfall trends in this region during the month of January are coincident with increasing frequencies of synoptic patterns found to be associated with lake-induced snowfall. Thus, secular variations of the large-scale atmospheric circulation are likely to be an important contributor to the observed positive trend in January snowfall in the snow belt region of the eastern Great Lakes. No relationship between variations in lake surface conditions and the snowfall trends are apparent.