Severe weather is expected to bring subzero temperatures the northern Plains as soon as Thursday, then reach the Mississippi Valley, the Northeast and the Ohio Valley by Sunday.

A potentially historic, massive winter storm will slam more than half of the United States today, moving east as it brings heavy snow, widespread ice accumulation and dangerous cold.

Meteorologists and public officials said the storm’s southern flank could endure a rare and damaging ice event capable of bringing down trees and power lines and causing prolonged power outages, while...