Thermal Convergence Over the Lake
Thermal convergence occurs over Lake Superior when land breezes converge over the lake. Land breezes result when cold air over the land drains out over the lake and pushes the warmer less dense air over the lake upward. The convergence helps to organize and strengthen bands of snow over the lake. Often a single band or a dominant band forms. If winds over the lake have an onshore component, the band can move into Duluth.