Lake-effect snow

Lake-effect snow is produced when cold air moves over a body of warmer lake water. The cold air collects the water vapor from the lake and rises, making clouds that are then carried downwind. When the vapors freeze, they start to precipitate as snow.

Lake Effect snow on January 10 2022

Snow over areas of salt water is called ocean-effect or bay-effect snow.

Sometimes, thundersnow (snow with lightning and thunder) may happen with lake-effect snow. This is because there is more instability and energy in the atmosphere.

Formation

Many things can affect lake-effect snow. They are: instability, fetch, wind shear, upstream moisture, upwind lakes, synoptic (large)-scale forcing, orography/topography, and snow or ice cover.

Instability

In order for lake-effect snow to form, there needs to be a 13 °C (23 °F) temperature difference between the lake and the air at about 1,500 m or 5,000 ft. When there is more instability, lake effect snow can form better.

Wind shear

Directional shear is very important for the making of snow squalls. Weak shear usually produces more powerful snow squalls than strong shear.

Topography

Lake-effect precipitation typically increases with elevation.

Examples

North America

Great Lakes

In the Great Lakes region in North America, when cold air is blown from the northwest, usually by a cold front, it picks up the moisture from the lakes. The moisture forms clouds which end up dumping inches of snow on the southern and eastern shores of the Great Lakes.