Winter storm threatens U.S. as crews treat roads and residents stock up.

Governors declared emergencies as a winter storm is expected to bring heavy snow, freezing rain and subzero wind chills across a wide area; crews are treating roads with salt and brine while residents have been stocking up on supplies.

A large winter storm is forecast to move across much of the United States beginning Friday, bringing heavy snow, sleet and freezing rain to regions from New Mexico to New England. Multiple governors declared states of emergency to help coordinate state and local responses. Transportation crews are treating roads with salt and brine, and residents have been purchasing batteries, ice melt and flashlights. Forecasters warned of subzero wind chills in parts of the Northern Plains and the potential for icy conditions that could affect power lines and trees. What is known: - Governors in several states declared emergencies to streamline coordination and access to support. - Road crews have been pretreating and spreading salt or brine; rain has complicated pretreatment in some locations. - Schools, sports events and community gatherings have been postponed or canceled in affected areas. - The National Weather Service forecast heavy snow, freezing rain and very low wind chills, with the storm expected to begin Friday. Summary: Officials and communities are taking preparatory steps to reduce travel and infrastructure risks as the storm approaches. The storm is expected to begin Friday; how extensively services and infrastructure will be affected is undetermined at this time.