What is the difference between freezing rain, sleet, snow, hail and graupel?
Precipitation can take a variety of forms with each one posing its own hazards.
Much of the precipitation that falls throughout the year begins as snowflakes high in the clouds. The snowflakes form as air rises, cools and condenses, usually around an area of low pressure.
Whether or not precipitation remains snow or transitions to rain, freezing rain, sleet, hail or graupel by the time it reaches the ground hinges on the temperature fluctuations the snowflakes may encounter as they travel through the layers of the atmosphere.
During the winter, driving under treacherous conditions requires your full attention and concentration. Knowing the common causes for accidents during the season can also help.
Here is an overview of five different types of precipitation, how they form and what hazards they can bring:
When the temperature between the ground and the clouds remains at or below the freezing mark (32 degrees Fahrenheit), precipitation will fall in the form of snow.
It is possible for snow to fall when temperatures are above 32, as long as the layer of above-freezing air near the surface is rather shallow, not allowing the snowflakes to melt.
A woman walks her dog as snow falls, Monday, Nov. 26, 2018, in Chicago. (AP Photo/Kiichiro Sato)
When the surface temperature is near or just above 32, the snow can be heavy and wet in nature. While this type of snow is great for making a snowman or snowballs, it is very difficult to remove from driveways, sidewalks and cars.
Dry, powdery snow that is easy to remove but can cause blowing and drifting problems is more likely when the air is drier and colder.
Regardless of the type of snow, slippery and dangerous travel can ensue for motorists, especially if the ground is cold enough for the snow to stick immediately.
Sleet vs. freezing rain
Sleet and freezing rain occur by a similar process, but are different forms of precipitation.
Sleet occurs when snowflakes melt into a raindrop in a wedge of warm air well above the ground and then refreeze in a layer of freezing air just above the surface. This results in frozen raindrops, or small ice pellets.
Freezing rain occurs when the wedge of warm air aloft is much thicker, allowing the raindrop to survive until it comes in contact with the cold ground. A coating of ice forms on whatever the raindrops contact.
"Freezing rain is by far the most dangerous because it forms a solid sheet of ice, as opposed to sleet that just has small ice pellets that quickly bounce off of the surface," AccuWeather Senior Meteorologist Brett Anderson said. "Actually, sleet can even provide a little bit of traction for drivers, as opposed to the obvious dangers of a solid sheet of ice that forms from freezing rain."
The additional danger with freezing rain is the potential for ice to accumulate on trees and power lines, possibly leading to damage and power outages.
Icicles, formed by freezing rain and stiff winds, hang from a road sign along Interstate 84 in Troutdale, Ore., Wednesday, Jan. 18, 2017. (AP Photo/Don Ryan)
While snow, sleet and freezing rain are familiar precipitation types to most people, one that may be lesser known is graupel, also known as snow pellets.
Graupel forms when snowflakes are coated with a layer of ice. Graupel is typically white and opaque.
A comparison of sleet and graupel. (Image/National Weather Service)
Unlike hail or sleet, graupel is soft and can fall apart easily in your hand.
Graupel is also usually smaller than hail, with a diameter of around 0.08-0.2 of an inch.
Hail is a chunk of a ice that can fall during thunderstorms.
Unlike snow, sleet, freezing rain and graupel, which occur in colder weather, hail is most common in warm conditions.
The size of the ice can vary based on the strength of the thunderstorm, with the largest hail comparable to the size of a softball.
A car sits with its rear window smashed in Omaha, Neb., Friday, June 30, 2017, after thunderstorms unleashed a barrage of hail on eastern Nebraska and western Iowa, shattering windshields, damaging roofs and shredding field crops and urban gardens. (AP Photo/Nati Harnik)
The larger the hail, the greater the risk of damage to cars, roofs, siding and crops.
Any livestock or person that is outside when a hailstorm strikes can be at risk of life-threatening injuries.
In the United States, the largest hailstorms typically occur in the High Plains.Report a Typo