It’s hard for most people imagine 6 feet of snow in a storm like the Buffalo area has seen recently, but such extreme snowfalls sometimes occur along the eastern edges of the Great Lakes.
The phenomenon is called “lake effect snow”, and lakes play a crucial role.
It starts with the cold, dry air of Canada. As the biting cold air sweeps over the relatively warmer Great Lakes, it sucks in more and more moisture which falls as snow.
I’m a climatologist at UMass Amherst. In the climate dynamics course I teach, students often ask how cold, dry air can cause heavy snowfall. Here’s how it goes.
How dry air turns into snowstorms
Lake effect snow is strongly influenced by the differences between the amount of heat and moisture on the surface of the lake and in the air a few thousand feet above.
Great contrast creates conditions that help draw water from the lake, and therefore more snowfall. A difference of 25 degrees Fahrenheit (14 Celsius) or more creates an environment that can fuel heavy snowfall. This often happens in late fall when the lake water is still warm from summer and cold air begins to blow in from Canada. More moderate lake effect snows occur each fall under less extreme thermal contrasts.
The path of the wind on the lakes is important. The more cold air moves over the surface of the lake, the more moisture evaporates from the lake. A long “fetch” – the distance over water – often results in more lake effect snow than a short one.
Imagine a perfectly aligned westerly wind blowing the entire 241-mile length of Lake Erie. That’s close to what Buffalo experienced during the storm that started Nov. 17, 2022.
Once the snow hits dry land, the altitude contributes an additional effect. Land rising from the lake increases the lift of the atmosphere, increasing rates of snowfall. This mechanism is called “orographic effect”. The Tug Hill Plateau, located between Lake Ontario and the Adirondacks in western New York, is well known for its impressive snowfall.
In a typical year, annual snowfall to lee or lee of the Great Lakes approaches 200 inches in some places.
Residents of places like Buffalo are well aware of the phenomenon. In 2014, parts of the region received over 6 feet of snow during an epic lake effect event from November 17-19. The weight of the snow collapsed hundreds of roofs and left more than a dozen dead.
Lake effect snowfall in the Buffalo area is generally confined to a narrow region where the wind blows directly off the lake. Drivers on Interstate 90 often go from sunny skies to a blizzard and back to sunny skies for 30 to 40 miles.
The role of climate change
Does climate change play a role in the lake effect snow machine? In a measure.
Fall has warmed up in the upper Midwest. The ice prevents the water in the lake from evaporating into the air and it forms later than in the past. The warmer air in the summer led to warmer lake temperatures in the fall.
Models predict that with further warming, more lake effect snow will occur. But over time, the warming will bring more precipitation in the form of lake-effect rain, which already occurs in early fall, rather than snow.
This article was updated on November 20, 2022, with snowfall reaching 6 feet.
This article was originally published on The conversation by Michael A. Rawlins at UMass Amherst. Read the original article here.