On November 17, 2014, a blast of frigid polar air began sweeping across the warmer water and warmer surface air of the USA’s Great Lakes. As the surface air uplifted with the surrounding terrain, it condensed into monster bands of snow that buried lakeshore communities from Western Michigan to Upstate New York in record snowfall.
Between November 17 and 21, communities on Lake Erie in and around Buffalo, NY received up to 88 inches (225cm) of snow. Normal total for an entire year in that area is 96 inches (244cm). Nearly a year’s worth of snow fell in 5 days. Heavy lake effect snowfall hit numerous other communities on the lee shores of Lakes Ontario, Michigan, Superior, and Huron.
Lake effect snow occurs when there is a difference of at least 13°C (23°F) between the air temperature and the water temperature. In the case of the November, 2014 storm, the polar air was unusually cold and the water in Lake Erie unusually warm. Normal late November water temperature in Lake Erie is 47°F. At the time of the storm, the lake water registered 54°F. The polar air mass that swept down through Canada registered near 0°F, a fifty-degree difference.
When that much variation exists, extreme amounts of moisture rise from the lake, and snow can fall at the rate of 5 to 6 in. (130-150cm) an hour. Lake effect snow usually occurs during the fall months when there is open water, before the lake freeze over. Once frozen, the moisture is locked under the ice. However, annual ice cover on the Great Lakes has decreased by 71% since 1973, giving lake effect snow a longer season.
It takes two to tango. Lake water is getting warmer due to our current global warming cycle. The same global warming cycle has hit the Arctic region especially hard, altering the behavior of the polar jet stream. The Arctic Ocean freezes much later than it did a few years ago and thaws much earlier, leaving open ocean for longer periods. The ice-free ocean reflects heat from the sun back into the atmosphere, slowing the polar jet stream and allowing it to sag and dip down into the American Midwest, instead of maintaining its historical course of blowing across the top of the world.
As air temperatures climb with global warming, lake water will continue to warm and Arctic oceans will become more ice free. The polar jet stream will probably continue to dip south. Monster lake effect snow storms may very well become the rule rather than the exception.