Thundersnow rolled through parts of western Pennsylvania overnight, showing up on a doorbell camera in Westmoreland County. 

Video from Mt. Pleasant shows snow blowing across the camera before there's a flash of lightning, followed by a loud crack and rumble of thunder. First Alert Meteorologist Ray Petelin says he got several reports of thundersnow as a front moved in. 

What is thundersnow? 

According to the National Oceanic and Atmospheric Administration, thunderstorms are less common in the winter, but thundersnow happens when lightning occurs during a snowstorm. 

Thundersnow can be found where there is relatively strong instability and abundant moisture above the surface, like above a warm front, the NOAA says. 

The National Weather Service says thundersnow generally produces high snowfall rates, and blowing and drifting snow or snow that has become compacted can lead to road hazards. 

While thundersnow is rare, it's not the first time the Pittsburgh area has seen it. A winter storm system brought a brief round of thundersnow last December.

More snow on the way for western Pennsylvania

The Pittsburgh area isn't done with snow. More is on the way this weekend.

The next big storm system is expected to arrive on Saturday night, and the probabilities of impactful snow and accumulation are increasing. 

An early snowfall forecast for Saturday into Sunday shows about 1 to 2 inches for northern counties like Beaver and Butler, 2 to 4 inches for southern counties like Allegheny and Washington, and 4 to 6-plus inches in the ridges.