NEW YORK — A major blast of winter weather tracking to hit the U.S. with icy conditions from New Mexico to the Carolinas and heavy snowfall up to New England has airlines posting flexible rebooking policies for potentially impacted passengers.

An estimated 100 million people in the U.S. are under some type of winter weather watch, warning or advisory on Wednesday ahead of the storm, the National Weather Service said.

The storm, expected to begin Friday and continue through the weekend, is also projected to bring heavy snow and all types of wintry precipitation, including freezing rain and sleet. An atmospheric river of moisture could be in place by the weekend, pulling precipitation across Texas and other states along the Gulf Coast and continuing across Georgia and the Carolinas, forecasters said.

AIR CANADA & WESTJET TRAVEL ALERTS

Ahead of the storm, Air Canada has posted winter operations travel alerts for a number of U.S. cities, allowing passengers travelling to and from those cities on the listed dates to change their flights free of charge.

Here’s Air Canada’s list …

Jan. 23 – Dallas (DFW)

Jan. 24 – Dallas (DFW), Nashville (BNA) and Raleigh Durham (RDU)

Jan. 25 – Boston (BOS), Cleveland (CLE), New York (EWR), New York (JFK), New York (LGA), Philadelphia (PHL), Pittsburgh (PIT), Raleigh Durham (RDU), Washington (DCA) and Washington (IAD)

Jan. 26 – Boston (BOS), Raleigh Durham (RDU), Washington (DCA) and Washington (IAD)

More information for Air Canada passengers can be found here.

WestJet is also offering its flexible rebooking policy, currently for travel on or between Jan. 24 – 25, to / from Atlanta, GA and Houston, TX (G. Bush Intercontinental).

More information for WestJet passengers can be found here.

FOUR MAJOR U.S. HUB AIRPORTS IN THE PATH OF THE STORM

About half an inch of ice – or 1.27 centimetres – can lead to a crippling ice storm, toppling trees and power lines to create widespread and long-lasting power outages. The latest forecasts from the National Weather Service warn of the potential for a half-inch of ice or more for many areas, including parts of Arkansas, Louisiana, Alabama and Tennessee.

At least four major U.S. hub airports are in the path of the southern storm this weekend, when ice, sleet and snow could delay passengers and cargo: Dallas-Fort Worth; Atlanta; Memphis, Tennessee, and Charlotte, North Carolina. Still more major airports on the East Coast could see delays later, as the storm barrels east.

Meanwhile parts of at least 19 states in the storm’s path were under winter storm watches by late Wednesday, with more watches and warnings expected as the system approaches. They include Texas, New Mexico, Oklahoma, Kansas, Missouri, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Tennessee, North Carolina, South Carolina, Kentucky, Indiana, Illinois, Ohio, Virginia and West Virginia. An estimated 55 million people are included in these winter storm watches, the weather service said.

With file from The Associated Press