Lake-Effect Snow

Syllabus: General Studies Paper 3

Bitter cold air sweeps across the relatively warmer Great Lakes, it sucks up more and more moisture that falls as snow. These extreme snowfall events happen periodically along the eastern edges of the Great Lakes of North America. The phenomenon is called “lake-effect snow,” and the lakes play a crucial role.

Lake-Effect Snow Formation

• Lake-effect snow is strongly influenced by the differences between the amount of heat and moisture at the lake surface and in the air a few thousand feet above it.
• A big contrast creates conditions that help to suck water up from the lake, and thus more snowfall. 
• A difference of 25 degrees Fahrenheit (14 Celsius) or more creates an environment that can fuel heavy snows. 
• This often happens in late fall, when lake water is still warm from summer and cold air starts sweeping down from Canada. 
• More moderate lake-effect snows occur every fall under less extreme thermal contrasts.
• The wind’s path over the lakes is important too. The farther cold air travels over the lake surface, the more moisture is evaporated from the lake. 
• A long “fetch” – the distance over water – often results in more lake-effect snow than a shorter one.

Will climate change affect lake-effect snow?

• Human-caused climate change has the potential to intensify lake-effect snow events, at least in the short term, according to the NOAA’s U.S. Climate Resilience Toolkit.
• “Ice cover extent and lake water temperatures are the main controls on lake-effect snow that falls downwind of the Great Lakes,”.
• The predictions change once lake temperatures rise to a point when much of what now falls as snow will instead fall as rain.”
• Lake-effect snow frequently pummels the Great Lakes with feet of wet snow that can trap people in their homes and covers cars.