Elmira, N.Y. (WETM) – Another major winter storm is expected to strike the Twin Tiers later this week, and it could not only give the region snow, but a mix of freezing rain and sleet as well.

Freezing rain and sleet are formed through the same process: raindrops falling from a layer of warm air aloft and into a layer of cold air near the ground. The difference between the two precipitation types depends on how thick the layer of cold air is.

When the cold layer is less thick than the warm layer, freezing rain forms. The raindrops are “freezing” in the cold layer, but they do not have enough time to completely freeze into ice pellets before hitting the ground. Instead, the drops freeze completely on the ground, resulting in a coating of ice on the roads.

Sleet forms when the cold layer is thicker than the warm layer. Raindrops in this case have enough time to completely freeze into ice pellets before hitting the ground. Those ice pellets are what we call “sleet.”

Both types of precipitation can lead to hazardous road conditions. Drivers should be extra cautious when driving on bridges, which freeze faster than roads paved on the ground. This is because a large part of bridges are surrounded by cold air.

The National Weather Service (NWS) advises everyone to take it slow when driving in ice and snow. Check out NWS’s website for more information on winter weather safety.