ATLANTA — Flight cancellations piled up and state officials warned of continuing dangerous roads Saturday in the wake of a winter storm that closed schools and disrupted travel across parts of the Southern United States.

Snow will turn into sleet and freezing rain along parts of the Southeast, as well as southern Arkansas, the weather service reported. Forecasters warn that icy conditions, between a tenth and a quarter inch of ice, will make travel dangerous for many. Power outages and downed branches are also a concern.

Twenty states, from Texas to Delaware, were on alert Friday for snow and ice as the storm continued to move across the South.