Why is thunder very common with rainstorms but relatively rare with snowstorms?
Jennifer Blitz, Chicago
Thunderstorms do occur with snow in Chicago, though usually only once every few years. Thundersnow is rare because the cold environment of a winter storm system usually lacks the atmospheric buoyancy to build clouds to altitudes that produce lightning, while tropical air in the warm season commonly does. However, powerful winter storms can produce thundersnow with impressive snowfall rates as high as four inches an hour. Several episodes of thundersnow occurred during Chicago’s 2011 Groundhog Day blizzard, and on Dec. 15, 1987, the city was buried by eight inches of thundersnow in just four hours. Thunder can also occur with lake-effect snow, a product of extreme instability caused by arctic air passing over the Great Lakes’ warmer waters.