Lake-Effect Snow: A Weather Phenomenon That Brings Heavy Snowfall to the Great Lakes Region
When towns along the Great Lakes are buried in drifts of blowing snow, like they have been in recent days, weather experts start talking about the "lake effect." Lake-effect snow often occurs in relatively narrow bands that dump copious amounts of snow. The weather phenomenon can drastically increase snowfall totals, and it may slam one area and leave another just miles away untouched.
How it Works
Lake-effect snow begins when cold air, often from Canada, blows in over the Great Lakes’ warmer waters. Warming air from the lakes then pushes the moisture in the sky higher into a zone most conducive to snowfall because of its temperature. This creates clouds capable of dumping lots of precipitation downwind, said Phillip Pandolfo, a meteorologist in the National Weather Service’s office in Buffalo, New York.
Most of the moisture needed for lake-effect snow does not actually come from the lakes, but rather from cold air that blows over them. "It’s a common misconception that the lakes are a tremendous source of moisture," Pandolfo said. "In practice, we actually need the air to actually have enough moisture in it before it really starts going over the lakes."
Clouds Form, Snow Falls
With the right conditions, the rising, moisture-laden air causes clouds to form that could bring "some really intense snowfall rates," Pandolfo said. The results typically are thin bands of clouds that can produce heavy snowfall – 2 to 3 inches per hour and sometimes more. And because the bands are narrow, towns near each other could see significant differences in snowfall totals.
Forecasting Lake-Effect Snow
Forecasting lake-effect snow can be difficult; slight changes in wind direction can have a major impact on where the heaviest snow falls, according to the weather service.
Heavy Snow is a Fact of Life Near Great Lakes
Lake-effect snow goes hand-in-hand with living near a Great Lake. In many cases, a foot or two of snow will fall, but occasionally it can get out of hand. In November 2022, lake-effect storms dumped more than 6 feet of snow in western New York. Those wintry storms were the worst in New York since at least November 2014, when some communities south of Buffalo were hit with 7 feet of snow over the course of three days, collapsing roofs and trapping drivers on a stretch of the New York State Thruway.
In parts of Michigan’s Upper Peninsula, snowfall can total more than 20 feet a year as the lake effect bolsters storms, according to researchers at the University of Michigan and Michigan State University. The phenomenon can also happen with other very large lakes, including the Great Salt Lake in Utah.
Frequently Asked Questions
Q: What is lake-effect snow?
A: Lake-effect snow is a weather phenomenon that occurs when cold air passes over the Great Lakes, causing the moisture in the air to rise and form clouds that produce heavy snowfall.
Q: Where does the moisture for lake-effect snow come from?
A: Most of the moisture needed for lake-effect snow does not actually come from the lakes, but rather from cold air that blows over them.
Q: Why is forecasting lake-effect snow difficult?
A: Forecasting lake-effect snow can be difficult because slight changes in wind direction can have a major impact on where the heaviest snow falls.
Q: How much snow can fall in the Great Lakes region?
A: In some parts of Michigan’s Upper Peninsula, snowfall can total more than 20 feet a year as the lake effect bolsters storms. In rare cases, heavy snowfall can exceed 6 feet in a single storm, as seen in western New York in November 2022.
