Thunder Snow, The thundersnow storm that produced thunder and lightning over parts of Chicago today is a phenomenon seen often in Colorado, Montana and on the shores of Lake Ontario, but is a relatively rare occurrence here.
Simply put, thundersnow is “the same thing as a thunderstorm, except instead of rain, you’ve got snow falling,” said National Weather Service meteorologist Jamie Enderlen.
Thundersnow is caused by vigorous updrafts within winter storm systems, often induced by a powerful jet stream. Air is sucked up into the clouds, where the moisture condenses and falls down as snow. Meanwhile, the intensity of the updrafts creates turbulence that is powerful enough to spark lightning.
Such atmospheric instability is less common in the wintertime, which is why thundersnow happens with less frequency than summertime thunderstorms.
Today’s storm was forecast to dump four to eight inches of snow on the Chicago area in a matter of mere hours.
WGN meteorologist Tom Skilling said the lake was not a factor in the storm, which blew in from the southeast.