A potentially historic winter storm will pelt much of the U.S. with devastating ice and heavy snow

More than half of the United States is set to face one of the most widespread and dangerous winter storms in years, threatening to deliver a potentially historic blow of snow and ice.

The long-running storm begins Friday and will dump a foot or more of snow and devastating amounts of ice along a 1,500-mile path from Texas to the Northeast by late Monday.

Northeast cities such as New York and Philadelphia may experience the most snow in at least four years, while major cities in the South face alarming amounts of snow.

More than 120 million people in two dozen states are under winter storm alerts — a number expected to rise Thursday.

Major travel disruptions to roads and airports are expected throughout the storm’s footprint, and widespread and potentially long-lasting power outages are also possible, especially in the south from its ice storm.

The extreme and record-breaking cold makes the storm and its effects worse by quickly accumulating snow and ice on roads, and possibly leaving those shivering without heat for days.

Travel and power outage effects may persist through at least early next week in areas that see significant snow and ice accumulation.

Here’s the latest on the storm:

Track shifts, with big effects

The track of this storm has been clear for a few days and has moved towards the north.

That shift still affected much of the Midwest and Northeast with heavy snow, bringing devastating ice to much of the South.

Its track can still change slightly, and that can affect the exact amount of freezing rain, sleet and snow each region receives, with dramatic effects.

“Even small changes can lead to large changes in local impacts,” the Weather Forecast Center said.

It all starts on Friday in the Plains where the storm’s vast pool of moist air begins to clash with arctic air. Over the weekend, cooler temperatures will continue to feed the storm’s expanding footprint east and northeast, spanning more than two dozen states from the Plains to the south and northeast.

The storm will move out of New England by late Monday, spreading more snow and strong winds across the region and contributing to more travel disruptions.

Ice can power out many

Ice damage from freezing rain is one of the most serious storm hazards.

Freezing rain forms ice on surfaces, and its added weight can bring down trees and power lines. In the worst-case scenario for this storm, the amount of ice could cause several power outages, some lasting longer. But power outages are expected even in the most unlikely scenario.

Parts of northern and eastern Texas through the lower-Mississippi and Tennessee valleys, northern Georgia and parts of the Carolinas and Virginia are at greatest risk for significant icing and power outages based on current forecasts. These include major cities such as Dallas-Fort Worth, Shreveport, Louisiana, Memphis, Tennessee, Huntsville, Alabama, and Charlotte, North Carolina.

Parts of metro Atlanta could see effective ice as well, but it’s more uncertain due to cold air coming in from the north and an increase in warm air from the south.

Even a small amount of ice can stop travel in major cities.

Threat of heavy snowfall from Terai to East Coast

Heavy snow will accumulate over a wide area north of the storm’s freezing rain zone.

Snow totals of 6 to 12 inches are likely in parts of more than a dozen states stretching from Oklahoma and Kansas to the Mississippi and Ohio valleys and into the Mid-Atlantic and Northeast. Some could see more than a foot of snow.

Oklahoma City and Tulsa, Oklahoma, Louisville, Kentucky, Washington, DC, and New York City are all in this snow zone. In some locations, snow may fall at rates of an inch or more per hour at times.

Tulsa could see a foot of snow for the first time in nearly 15 years. Paducah, Kentucky will receive a foot of snow for the first time since March 2015.

New York City and Philadelphia could see their first snowfall of 6 inches or more in nearly four years.

The Plains, Midwest, and South may experience cold or freezing rain along the southern edge of the snow zone, complicating forecasts and making possible snowfall totals less certain. Parts of the I-95 corridor in Washington, DC, New York City may also mix with snow followed by cold and freezing rain.

States are preparing for the worst

At least three states – North Carolina, South Carolina and Georgia – declared states of emergency in effect ahead of the storm’s arrival.

“I encourage all North Carolinians to stay home and off the roads this weekend unless absolutely necessary so that first responders can do their jobs safely and effectively,” North Carolina Governor Josh Stein said in a news release.

Crews across North Carolina, Arkansas and Texas were treating roads and bridges, but officials warned the effects would last into the next week.

Georgia’s state of emergency will last seven days with the impending winter storm due to its long-term nature, Gov. Brian Kemp said Thursday. Kemp said he has authorized 500 National Guardsmen to be called on standby as needed. The Georgia Department of Transportation will begin treating roads early Saturday morning.

“Take this time to secure food, fill up on gas and make sure you’re prepared for any potential power outages,” Georgia Gov. Brian Kemp urged Wednesday.

In Texas, Gov. Greg Abbott activated the state’s emergency response resources on Tuesday to prepare roads, personnel and equipment ahead of the storm. The agencies will also monitor electric and natural gas utilities.

Chance of record cold

The arctic cold front that will feed this winter storm will arrive in the Midwest and Plains Thursday through Friday and then spread south and east this weekend. Dozens of locations could break record daily high and low temperatures, especially this weekend and early next week.

Most of the Midwest and Terai will see temperatures below 30 degrees below average by Friday. This is important in mid to late January when average temperatures are already at their lowest in many places east of the Rockies.

The worst of the cold front will push into parts of the South and spread into the Northeast on Saturday, plunging thermometers 20 to 40 degrees colder than average.

Dallas-Fort Worth could break record lows Sunday and Monday morning, possibly dipping into the single digits on Monday. Shreveport, Louisiana could do the same when lows drop into the teens on Monday and Tuesday morning.

CNN meteorologist Briana Waxman and CNN’s Ella Nielsen contributed to this report.

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