A cross-country storm, a blast of Arctic air and an outbreak of showers and thunderstorms are threatening to snarl traffic and pile up delays at airports over the Thanksgiving holiday weekend, one of the nation's busiest travel periods.

A powerful winter storm packing heavy snow, rain and even severe weather is set to snarl Thanksgiving travel in the eastern half of the U.S. after first walloping the West with winter weather that led to celebrations at ski resorts ahead of the holiday.