Article courtesy of 90.9 wbur Boston's NPR news station

LAURA LORSON, BYLINE: You can hear the hiss of - I think we call it graupel - little, little ice droplets kind of hitting the windows.

BLOCK: That's Laura Lorson of Kansas Public Radio, who along with lots of people in the Midwest, also experienced what we're hearing now, thundersnow.

LORSON: And I saw a flash of lightning and I heard a very bassy(ph) boom of thunder, which had seemed extraordinarily loud because I think it had been then so quiet.

BLOCK: Thundersnow came as a surprise to Kansans. Meteorologist Lee Grenci says most people think thundersnow is rare.

LEE GRENCI: But actually it's not. If you think of a thunderstorm in the middle of July on a hot 95-degree day over Washington, D.C., four miles away, there's thundersnow. By four miles away, I mean straight up in the air - there's snow and there's thunder. So the only difference between a July thunderstorm, when the snowflakes four miles over your head eventually melt into rain, is that with thundersnow during winter the snow actually reaches the ground.

BLOCK: Grenci knows thundersnow not just professionally. A dozen years ago, he encountered it at home at three in the morning.

GRENCI: I ran outside in my pajamas and it was snowing to beat the band. And then, out of the blue, there are these peels of thunder and flashes of lightning. It's surreal.

BLOCK: As Laura Lorson pointed out today, along with the thundersnow there was something else - a pellet form of snow called graupel

GRENCI: Graupel is a rind snowflake. By that I mean the snowflake is falling and it's either picking up little drops of super-cooled water - small drops of water that can survive and not freeze down to temperatures as low as minus 40 degrees. These snowflakes start to pick up these super-cooled drops of water and they turn into little ball of ice called graupel or soft hail.

BLOCK: Meteorologist Lee Grenci, he blogs for Weather Underground and spoke to us from State College Pennsylvania. He cautions that lightning strikes during thundersnow are just as dangerous as any in a thunderstorm, but since fewer people are outside you rarely hear reports of people being struck. Transcript provided by NPR, Copyright NPR.