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A woman shovels snow off her car, not visible under the piles.
Parts of the Buffalo area saw more than 6 feet of snow over three days in November 2022. AP Photo/Joshua Bessex

What causes lake-effect snow like Buffalo’s extreme storms?

It’s hard for most people to imagine more than 4 feet of snow in one storm, but such extreme snowfall events happen along the eastern edges of the Great Lakes.

The phenomenon is called “lake-effect snow.”

It starts with cold, dry air from Canada. As the bitter cold air sweeps across the relatively warmer Great Lakes, it sucks up more and more moisture that falls as snow.

A satellite image shows wind blowing snow across Lakes Superior, Michigan, Huron, Erie and Ontario on Nov. 20, 2014
Canadian winds pick up moisture over the Great Lakes, turning it into heavy snowfall on the far shore. NOAA

I’m a climate scientist at UMass Amherst. In the Climate Dynamics course I teach, students often ask how cold, dry air can lead to heavy snowfall. Here’s how that happens.

How dry air turns into snowstorms

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.

Illustration of how wind comes over the lake and moisture condenses moving up elevation
How lake-effect snow works and why western New York get such powerful storms. Image from 'The AMS Weather Book' by Jack Williams. © 2009 by the American Meteorological Society. Used with permission.

The wind’s path over the lakes is important. 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.

Imagine a wind out of the west that is perfectly aligned so it blows over the entire 241-mile length of Lake Erie. That’s close to what Buffalo experienced during a storm that brought 6 feet of snow to the region in November 2022.

An animation overlays wind direction on satellite imagery of snow accumulation during a lake-effect event.
Wind directions from a storm in 2016 show how lake-effect snow piles up. NOAA

Once the snow reaches land, elevation contributes an additional effect. Land that slopes up from the lake increases lift in the atmosphere, enhancing snowfall rates. This mechanism is termed “orographic effect.” The Tug Hill plateau, located between Lake Ontario and the Adirondacks in western New York, is well known for its impressive snowfall totals.

In a typical year, annual snowfall in the “lee,” or downwind, of the Great Lakes approaches 200 inches in some places.

Residents in places like Buffalo, New York, are keenly aware of the phenomenon. In 2014, some parts of the region received upwards of 6 feet of snowfall during an epic lake-effect event. The weight of the snow collapsed hundreds of roofs and led to over a dozen deaths.

Two people shovel knee-deep snow off a roof.
A lake-effect snowstorm in November 2014 buried Buffalo, N.Y., under more than 5 feet of snow and caused hundreds of roofs to collapse. Patrick McPartland/Anadolu Agency/Getty Images

Lake-effect snowfall in the Buffalo area is typically confined to a narrow region where the wind is coming straight off the lake. Drivers on Interstate 90 often go from sunny skies to a blizzard and back to sunny skies over a distance of 30 to 40 miles.

The role of climate change

Is climate change playing a role in the lake-effect snow machine? To an extent.

Fall has warmed across the upper Midwest. Ice prevents lake water from evaporating into the air, and it is forming later than in the past. Warmer summer air has led to warmer lake temperature into fall.

Models predict that with additional warming, more lake-effect snow will occur. But over time, the warming will lead to more of the precipitation falling as lake-effect rain, which already occurs in early fall, rather than snow.

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