The winter storm that blanketed most of Missouri with snow and ice included a rare feature — thunder.
The phenomenon, known as "thundersnow," is extremely rare and is caused by instability in the atmosphere.
It happens when the ground is warm, but air in higher parts of the atmosphere is much colder. It also requires strong wind to push the warm air up and create the instability that results in thundersnow.
A University of Missouri climatology study shows that between 1961 and 1990 only 191 cases of thundersnow were reported.
Snowfall in mid-Missouri began just before 8 a.m. Thursday, accompanied by thunder and lightning.