What Determines if a Storm Drops Ice, Snow or Sleet?
A snow-covered statue of George Cohen looks over Times Square on Feb. 13. A winter storm dumped up to 10 inches of snow in New York City.
Snow falls in front of the U.S. Capitol building on Feb. 13, 2014 in Washington, D.C.
A person walks two kids to school during the snowstorm in New York City on Feb. 13. Despite official calls to otherwise stay at home, city schools remained open during the storm.
A worker clears snow from a sidewalk in Chevy Chase, Md., in the early hours of Feb. 13, 2014.
As the latest winter storm blasts the East Coast of the U.S., millions of people are facing another day of freezing conditions that have triggered school and government office closures and thousands of cancelled flights. Seen here, the U.S. aircraft carrier Intrepid is surrounded by floating ice on the Hudson River in New York.
A family surveys downed trees on their street, the results of the rare winter ice storm that swept across the South on Feb. 12, 2014 in Summerville, S.C.
Big, dirty piles of snow and ice, have collected throughout numerous snow storms this season, on the street in the Chelsea neighborhood of New York. Because of the cold weather the ice and snow has not melted and the city has left these deposits.
Atlanta roads prepare for the onslaught of a significant winter storm. The National Weather Service said, "The ice accumulations remain mind-boggling, if not historical."
Icicles form on a trash can as freezing rain falls in Augusta, Ga., on Wednesday, Feb. 12, 2014. Atlanta has a half-inch of ice and South Carolina is expecting up to an inch of ice by Thursday night.
The ice storm brought downtown Atlanta, Georgia, to a standstill as the temperatures continued to drop.
A GOES Satellite image shows the huge winter storm in the Southeastern United States. The storm will get colder as it moves slowly up the coast, dumping up to 10 inches of snow on Washington, D.C., and a foot on New York City.
The meat case at a local Greenville, Ga., supermarket is completely bare as residents on Tuesday braced for the impending storm.
Snow and ice will blanket much of the United States this week as a winter storm pounds the South and Northeast. This wintry weather leads us to wonder why we end up with icy roads on one bone-chilling day and snow -- or sleet -- on another?
Most precipitation begins as snow high in the atmosphere, where the temperature stays below 0 degrees Celsius (32 degrees Fahrenheit), the freezing point of water. As that snow falls, the temperature of the air and land determine whether the precipitation remains as snow, melts into rain, melts then refreezes into sleet, or covers the land in a treacherous layer of ice.
If the temperature from cloud to ground stays below zero, snowflakes drift to Earth. However, if a large enough band of warm air lies between the snowstorm and the ground, the snow melts into rain.
The situation gets complicated when a layer of air near the surface is above zero, while the ground remains below freezing, according to the Weather Underground. In this case the high altitude snow melts into rain, then refreezes into a slick layer of ice once the water hits the ground.
Meteorologists call this nasty phenomenon freezing rain, while commuters call it misery.
Sleet is another possible fate for the high-altitude snow. Tiny ice pellets form when the airborne snow melts into rain, then refreezes. For sleet to form, the layer of above-freezing air must be either thinner or warmer than in the conditions that create freezing rain.