The worst winter storm in more than a decade is forecast to affect tens of millions of Americans

Tens of millions of Americans are bracing for a major winter storm that could bring the heaviest snowfall and coldest temperatures in more than a decade.

The storm, which started in the center of the US, will move eastward in the coming days, the National Weather Service (NWS) announced.

Parts of the US not used to extreme cold, including Mississippi and Florida, were warned to expect dangerous conditions.

Forecasters say the extreme weather is caused by the polar vortex, an area of ​​cold air that circles the Arctic.

“For some, this could be the heaviest snowfall in more than a decade,” the National Oceanic and Atmospheric Administration said.

AccuWeather forecaster Dan DePodwin said, “This could lead to the coldest January for the US since 2011.”

He added that “temperatures well below the historical average” could persist for a week.

Such low temperatures will also be on the east coast, where storms are expected until Sunday evening.

The central U.S. will see “significant disruptions to daily life” and “dangerous or impossible driving conditions and widespread closures” through Sunday, according to the NWS.

Some areas of Kansas and Indiana could see at least 8 inches (20.3 cm) of snow.

Blizzards are also possible in parts of the Midwest.

“Whiteout conditions will make travel extremely hazardous, with impassable roads and a high risk of stranded motorists,” the NWS warned.

Sleet and freezing rain are forecast for Missouri, Illinois and parts of Kentucky and West Virginia.

As the storm moves east, millions of Americans will see record low temperatures, forecasters say.

Cities including Washington DC, Baltimore and Philadelphia are bracing for snowy and icy conditions Sunday through Monday. Snowfall between 5-12 inches could be seen in parts of Virginia.

Also on Sunday, parts of the southern US, including Arkansas, Louisiana and Mississippi, may see severe thunderstorms.

Private meteorologist Ryan Maue said: “It’s going to be a mess, a potential disaster. This is something we haven’t seen in a while.”

American, Delta, Southwest and United airlines are waiving layover fees for passengers due to potential flight disruptions.