Cold air moves across the warm lake water. The air warms becomes less dense and rises, and also becomes humid.
2: Warmer, Moist Air Rising
As the air rises, it begins to cool. This cooler and moister air starts to condense and forms fog, which eventually creates clouds over the lake.
3: Moist Air Condenses
Once the air moves over land, this moisture in the air will continue to condense and form precipitation, snow.
4: Warmed Condensed Air Slows
As the warmed air reaches the shoreline, the air moves slower due to the increase in the friction between the water and land. This causes the air to concentrate in certain areas.
5: Further Cooling and Snow
Higher land and hills (changes in topography) on the leeward side of the lake force the air upward. This causes the air to cool further leading to further cloud formation and increased snowfall.