Wild Winter Weather: Why Is Thundersnow So Rare?

Jan. 27, 2011— -- As if the sheer volume of snow dumped by last night's record-breaking storm wasn't shocking enough, East Coasters had front row seats to the rare weather phenomenon known as thundersnow.

From New York to Philadelphia to Washington, D.C., snowbound residents reported rumbles of thunder and bursts of lightning as the sixth storm in the past 30 days rolled through the region.

On Twitter, the mysterious meteorological event spawned a flurry of perplexed posts as people wondered what was going on with the unusually dramatic weather.

"Snow + thunder = snunder!! Mother nature is p***ed," wrote one Twitter user.

"Ok so we have a foot of snow and now thunder and lightning??? Pretty sure that means something bad...." posted another.

Other weather watchers had some fun playing around with the name of the seemingly freakish phenomenon.

One Washingtonian wrote ""Thunder Snow" would make a great sports team name. ('The New York Thunder Snow takes their winning streak on the road..')"

"Thunder snow should be an episode of flight of the concords," said a Twitter fan in Philadelphia.

But though thundersnow storms may be rare, meteorology experts say they are legitimate weather events with some predictive value for forecasters.

Robert Kelly, chief of forecast operations at the National Oceanic and Atmospheric Association (NOAA), said that the dynamics behind thundersnow are similar to the dynamics of any thunderstorm -- a strong, upward motion of warm, moist air.

The combination of warmer temperatures at the ground and cooler temperatures higher up generate thunder and lightning, he said. But those dramatic weather events rarely accompany snow because warm ground temperatures usually don't occur during snowstorms.