Keep in mind that forecast low-level shear and stability at a location south of a model simulated band may actually be favorable for the strengthening and maintenance of the band.
For a full picture of the shear profile, look at plan views of the shear across the entire area, not just forecast soundings for a few locations.
The freezing of Lake Erie may sometimes act to enhance convergence downwind of Lake Ontario (removal of other lakes in model simulations has resulted in more snow downwind of Lake Ontario).