That uncertainty is not unusual at this early stage. Forecasters rely on a blend of weather models — computer simulations used to predict future conditions — and they are more confident in a forecast when most of those models are consistent with one another. The closer the storm is, the more confident forecasters become.

Reporters from across the NPR Network are covering the storm in each state — the impact and how officials are responding.

About half the population of the United States is in the path of heavy snow and crippling ice, the National Weather Service said.

Gov. Tate Reeves says that seven winter-related deaths have occurred in Mississippi after a cold front over the weekend brought life-threatening temperatures from Arkansas to New England.