Around 10,000 to 12,000 years ago, at the end of the last glacial period, a massive sheet of glacial ice receded away from the northern United States. What was once covered by ice now revealed deep, cavernous rivers and basins. Over time, these carved out pieces of land would be filled with freshwater from the glacier itself as it melted away, and are now what’s considered the Great Lakes.
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These five deep freshwater lakes are located on the U.S. and Canadian border touching Ontario in Canada, Michigan, Wisconsin, Minnesota, Illinois, Indiana, Ohio, Pennsylvania and New York in the United States. Lake Superior, Huron, Michigan, Erie and Ontario, cover nearly 94,251 square miles and represent the largest surface of freshwater in the world. To give some perspective, that surface area is nearly the same size as the United Kingdom.
More than 30 million people, roughly 10 percent of the U.S. population, now call the Great Lakes region their home — a place where all four season occur with extreme weather at times. One of the most intense seasons is winter, especially along the shores of these magnificent lakes.
Lake-effect snow is nothing new to the people who live along these lakes. It is a term used frequently by meteorologists, especially between the months of November and February.
Lake-effect snow is created when cold air rushes across the relatively warmer waters of the lakes. As this occurs, warmth and moisture from the lake are transferred into the lower layers of the atmosphere.
This now warmer and wetter air mass will begin to rise. As it rises and moves away from the lake, it will cool and condense into ice crystals known as snow.
Snow bands created by this process could lead to intense, narrow strips of snow that could potentially produce 2 to 3 inches of snow per hour or more.
Wind direction plays a key role in where these lake-effect snow bands develop. Often times heavy snow will be falling in one location, but only a few miles away in either direction, there is no snow at all and the sun is shining.
You may remember hearing about the November 17-19th, 2014, lake-effect snow event near Buffalo. That event brought more than 5 feet of snow to areas just east of the city and barely any snow a few miles to the north. An additional 1-4 feet of snow fell during a second lake-effect event in some of the same areas a couple days later. Due to the amount of snowfall, piles of snow were still present by the month of July.
Lake-effect snow bands can sometimes reach the Miami Valley. While they can be dangerous, more times than not snow-squall events, created by the moisture from the lakes, lead to bigger problems. As discussed in a previous article, these quick bursts of snow can lead to white-out conditions and treacherous travel. Snow squalls have been known to be deadly with multi-vehicle pile ups on the expressway.
To come full circle, knowing the past of the lakes and what they are capable of, there is no question that the science surrounding the Great Lakes is impressive. The next time you hear me say “Lake-effect snow,” just think back to how they were created. If not for the glacial period, I would not be forecasting these types of weather events.
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