How lake-effect snow affects areas around the Great Lakes
When the air is cold, it can cause clouds to form above lakes, and these clouds can create heavy snowfall.
People walk in lake-effect snow on December 1, 2024 in Lowville, New York. Photo: APWhen towns along the Great Lakes in the United States get buried in drifts of blowing snow, weather experts start talking about the “lake effect”.
Lake-effect snow often occurs in relatively narrow bands that dump copious amounts of snow. This can drastically increase snowfall totals, and it may slam one area and leave another just miles away untouched.
In early December, parts of upstate New York, Pennsylvania, Ohio and Michigan saw nearly 1.2 metres of lake-effect snow.
While many people think lake-effect snow is caused by moisture from the lakes, it is actually from cold air that blows over them (see graphic).
“It’s a common misconception that the lakes are a tremendous source of moisture,” said Phillip Pandolfo, a meteorologist at the National Weather Service.
“In practice, we actually need the air to have enough moisture in it before it really starts going over the lakes.”
Clouds form, snow falls
The lake effect typically begins when cold air blows over a lake’s relatively warmer waters. Warming air from the lakes pushes the cold air’s moisture higher. With the right conditions, the rising, moisture-laden air forms clouds that could bring “really intense snowfall rates”, Pandolfo said.
The results typically are thin bands of clouds that can produce heavy snowfall – 5cm to 8cm per hour and sometimes more. Because the bands are narrow, towns near each other could see huge differences in snowfall.
According to the weather service, forecasting lake-effect snow can be tough; slight changes in wind direction can have a major impact on where the heaviest snow falls.
Heavy snow is a fact of life near the Great Lakes
Lake-effect snow goes hand in hand with living near a Great Lake. In many cases, 30cm to 61cm of snow will fall, but occasionally it can get out of hand.
The Great Lakes refer to the five large lakes in eastern North America. They are Lakes Superior, Michigan, Huron, Erie and Ontario. Together, they cover an area of about 245,660 sq km. They form the largest connected area of fresh water on Earth.
The Great Lakes affect the climate of the surrounding regions. They absorb a lot of heat in the summer and release it in the winter. As a result, the land closest to the lakes has cooler summers and warmer winters.
In November 2022, lake-effect storms dumped more than 1.8 metres of snow in western New York. These were the worst in New York since at least November 2014, when some communities were hit with 2.1 metres of snow over three days, collapsing roofs and trapping drivers on roads.
In parts of Michigan’s Upper Peninsula, snowfall can total more than six metres 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 the state of Utah.
Associated Press
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What is the difference between lake-effect snow and regular snow?
Unlike lake-effect snow, the latter forms when water vapour in the atmosphere cools and condenses into ice crystals. Snow can fall anywhere in the world where the temperature is cold enough.
Lake-effect snow usually happens near large lakes. Lake-effect snow is also a lot more intense and can last several days, while regular snow usually does not last as long.
It can be very dangerous for drivers too because the weather can change quickly. The weather may be clear in one area, but there could be heavy snow and poor visibility just a few kilometres away.