As the land warms more than the water, the difference in air temperature creates a difference in air pressure between the two surfaces. The resultant wind, known as a lake breeze, cools us off a few miles from the lakeshore, but often also creates a lake breeze boundary. That boundary between the cooler air from the lake and the milder air inland is significant meteorologically and can serve as a trigger mechanism for developing showers and even thunderstorms.
Tomorrow the lake breeze boundary looks to be most impressive off of Lake Erie. As the boundary drifts east off of Lake Erie, it could mean a shower or thunderstorm for areas southwest of Rochester.