What makes it sleet instead of snow

While all forms of precipitation start as snow high up in the clouds, there are four primary types that eventually reach the ground: snow, sleet, freezing rain and plain ol' rain. Snow occurs when the atmosphere is "cold" all the way from the clouds to down here at the surface. Sleet and freezing rain form because of a "warm-air sandwich" in the atmosphere above our heads. Precipitation starts as snow in the cold layer at the top, then melts to rain as it falls through the warm layer, then refreezes into sleet or freezing rain as it falls through the cold layer near the surface.

For sleet to occur, the warm air layer is rather thin. A thicker wedge of cold air beneath the warm air refreezes the partially melted snow into ice pellets. For freezing rain to occur, the warm air layer is thicker. The snow melts into rain then refreezes just as it hits the cold ground. Since the rain is not freezing until it reaches the surface, it still falls like regular rain and therefore looks and feels the same until it freezes on the ground.

Sleet is made up of ice pellets that bounce off objects. Even though this may sound more hazardous than freezing rain, that's not the case. Similarly to how sleet is formed, the rain droplets then fall into a cold layer of air. However, instead of fully freezing in a deep layer of cold air, the raindrops are super-cooled in a shallow layer of cold air.

While the droplets do not freeze into pellets, they do reach freezing temperatures. As a result, the droplets quickly freeze on contact with any surface with a temperature at or below freezing.

In the worst cases, freezing rain can leave a crippling coat of ice on cars and tree branches and cause widespread power outages. Hello, Dayton! You'll now find me on Channel 7 as the Weekend Meteorologist. These slushy drops refreeze as they next fall through a deep layer of freezing air above the surface, and eventually reach the ground as frozen rain drops that bounce on impact.

Depending on the intensity and duration, sleet can accumulate on the ground much like snow. Freezing rain occurs when snowflakes descend into a warmer layer of air and melt completely.

When these liquid water drops fall through another thin layer of freezing air just above the surface, they don't have enough time to refreeze before reaching the ground. Even light accumulations can cause dangerous travel, while heavier amounts can cause significant damage to trees and power lines.

A significant accumulation of freezing rain lasting several hours or more is called an ice storm. Most precipitation that forms in wintertime clouds starts out as snow because the top layer of the storm is usually cold enough to create snowflakes. Snowflakes are just collections of ice crystals that cling to each other as they fall toward the ground. Precipitation continues to fall as snow when the temperature remains at or below 32 degrees F from the cloud base to the ground.