CHICOPEE, Mass. (WWLP) – Snow, sleet and some freezing rain will be on the way Sunday night through Monday.
In the winter, when temperatures are right near freezing, rather than below, that can bring different forms of precipitation.
When the cold season hits and a storm is on its way, it doesn’t always just bring snow with it. This is especially true when temperatures are hovering near the 32-degree freezing mark rather than under it, like what tends to happen at the beginning and end of winter. That temperature variation can sometimes instead bring sleet and freezing rain. But what ultimately determines the precipitation type? Think of the atmosphere in columns, looking at the temperature of the air from the ground to way high up in the sky.
All precipitation starts high in the sky where it’s all snow since the air is so cold. With rain, there is a thick layer of air above freezing that allows the snow to fully melt into liquid before hitting ground.
With freezing rain, there is also a thick layer of warm air that allows the snow to melt into rain, but a shallow layer of below-freezing air that doesn’t allow enough time for the rain to freeze itself, but only once it touches objects on the ground that are subfreezing, like streets, sidewalks and your car.
Sleet occurs when that colder layer near the ground is thicker, so precipitation starts off as snow, melts in a warm layer into rain, and only partially refreezes into snow once it reaches that colder layer closer to the ground. Sleet and freezing rain happen usually when there’s an incoming front causing those different temperature profiles.
Snow is simpler and occurs when the entire column of air is below freezing, like what normally happens in the middle of winter on a bitterly cold day