Buzz
Some regions of the northeastern U.S. are facing a massive snowfall just ahead of Thanksgiving—especially in western New York, where lake-effect snow could accumulate to 'multiple feet.' You might have seen the huge snowdrifts this phenomenon creates, but what is the true cause behind it?
As you might expect, experiencing lake-effect snow requires a lake. The key factor behind lake-effect snow is the temperature difference between the lake and the air above it. Water’s high specific heat allows it to warm and cool much slower than the surrounding air. Throughout the summer, the lake absorbs heat, which lingers well into autumn. When the air turns colder, this difference in temperatures triggers the lake-effect snow.
As the chilly air moves over the lake, moisture from the water evaporates, warming the air right above the surface. This warm, moist air rises and condenses, quickly forming thick clouds. The rate at which temperature changes as you rise through the air is called the 'lapse rate'; the steeper the lapse rate, the more unstable the atmosphere is—and the greater the likelihood of it producing weather events.
Reaching the shore only intensifies the situation. The added friction causes the wind to decelerate and clouds to accumulate, while hills and varied terrain push the air upwards more forcefully, resulting in further cooling and condensation.
Other crucial factors influencing the specifics of a lake-effect snowstorm include the wind direction and the particular lake involved. Winds blowing along the length of a lake generate more 'fetch'—the area of water over which the wind travels—leading to more severe storms. The lake’s natural boundaries create sharp contrasts between heavy snow, light flurries, and even walls of snow moving toward the shore. The southern and eastern shores of the Great Lakes are known as 'snow belts' because the northwest winds tend to hit these areas hardest.
