JOHNSON COUNTY, Ind. (WXIN) — Several Hoosiers reported hearing thunder and seeing lightning while snow was falling earlier this week during a winter storm. The National Weather Service confirmed the phenomenon in Johnson and Brown counties, though it was reported elsewhere.
The NWS described the occurrence as “something unusual,” with lightning sensors picking up thundersnow in the area.
We typically associate thunder and lightning with thunderstorms accompanied by rain. Under certain conditions, however, snow can actually accompany a thunderstorm.
According to the National Oceanic and Atmospheric Administration (NOAA), thundersnow can occur when there is strong instability combined with abundant moisture above the Earth’s surface — such as a warm front.
NOAA said the conditions for thundersnow are similar to what happens during a typical thunderstorm. It’s rarer for this to happen with snow, however, because temperatures tend to be colder when snow falls, both at higher and lower points of the atmosphere.
“However, in some winter storms, shallow layers of warm air are lifted and continue to rise on their own – increasing snowfall and causing enough electric charge separation for lightning to occur,” the agency said.
The result: lightning and thunder accompanied by snow. NOAA also noted that thundersnow is typically associated with increased snowfall amounts.