This index, from NOAA's National Weather Service, attempts to scale the impacts from winter weather, taking into account factors such as snowfall, accumulated snow on rooftops, ice accumulation, the potential for a flash freeze, and blowing snow. Not all factors are in play in a given winter storm.

Half the U.S. population will likely see some effect from the sprawling storm that will move across the country this weekend, meteorologists said.

The season’s most extreme storm so far is set to lash the eastern half of the United States with damaging ice and heavy snow late this week. It’s all being fed by a brutal blast of Arctic air that’s bringing the season’s coldest air to date.

A winter storm bringing very cold temperatures is expected to slam a massive stretch of the United States this week with more than 175 million people facing the prospect of

A powerful winter storm is setting its sights on a wide swath of the Southeast and the lower Midwest this weekend, bringing a dangerous mix of snow, freezing rain, and ice that could significantly disrupt road travel and regional freight movement.

On Friday, as Texans head to sleep, a major winter storm will make its unwelcome arrival. By morning, roads across much of the state will be icy, and as much as five inches of snow and ice could accumulate in North Texas.

A potentially dangerous ice storm is setting its sights on north Georgia this weekend. Weather officials are warning of treacherous travel, possible power outages, and days of lingering cold as Arctic air moves in behind the system.