Lake-effect storms are mesoscale weather phenomena that appear as narrow bands of clouds that form over large bodies of water which are significantly warmer than the surrounding land areas. Cold, dry air flowing from the land meets warm, moist air over the lake, causing the moisture in the air to condense and form clouds. As the air continues to rise, it cools and condenses, forming clouds and precipitation. These storms can produce copious amounts of snow, especially if the temperature difference between the water and the air is large.

Here are the factors that contribute to the formation of lake-effect snow:

1. Large Temperature Difference: The most important factor for lake-effect storms is a significant difference in temperature between the lake and the surrounding air. The warmer the water and the colder the air, the greater the potential for lake-effect precipitation.

2. Wind Direction: The wind direction is critical in determining the direction and intensity of lake-effect snow. Strong winds blowing perpendicularly across the lake transport the cold air over the warmer water, creating conditions for lake-effect snow.

3. Atmospheric Stability: The atmospheric stability refers to the resistance of the atmosphere to vertical movement. Stable air masses are less likely to produce lake-effect precipitation because they inhibit vertical motion. Unstable air masses, on the other hand, favor convection, which promotes cloud development and precipitation.

4. Lake Size: The size of the lake plays a role in lake-effect snow. Larger lakes have a greater surface area, which provides more moisture and energy for lake-effect storms to develop.

5. Duration of Cold Airflow: The duration of the cold air flowing over the lake is important for the longevity and intensity of lake-effect storms. Continuous cold air supply maintains the temperature gradient and sustains lake-effect precipitation.

Therefore, when all of these factors come together, such as strong cold winds blowing across a large and relatively warm lake, it can result in significant lake-effect storms and heavy snowfall in downwind areas.