Millions of Americans from New Mexico to the Carolinas are preparing for a potentially catastrophic ice storm expected to begin on Friday and extend through the weekend, threatening widespread power outages, dangerous travel conditions and significant damage to infrastructure, meteorologists warned.

According to the U.S. National Weather Service (NWS), nearly 160 million people — almost half of the country’s population — are currently under winter storm watches, warnings or advisories. Alerts stretch from Arizona and Montana in the West to the Carolinas and Maine in the East.

Forecasters say the system will bring heavy snowfall, freezing rain, sleet and ice accumulation, with conditions expected to worsen as an atmospheric river of moisture develops and pushes precipitation into Texas and Gulf Coast states before moving northeast through Georgia, the Carolinas and into the Mid-Atlantic and New England regions.

Meteorologists along the East Coast warned that snowfall totals could reach a foot or more in major cities along the Interstate 95 corridor, including Washington, D.C., Philadelphia, New York City and Boston, potentially making travel extremely difficult or impossible.

In the Washington, D.C. region, the NWS cautioned that the combination of heavy snow, ice accumulation and prolonged frigid temperatures poses “a unique and significant threat to life and property” across the area.

Officials urged residents to prepare for extended power outages, avoid unnecessary travel and closely monitor official weather updates as the storm evolves.