Arctic storms have blanketed the U.S., threatening to break low-temperature records in the heartland, spread cold and snow from coast to coast, and cast a chill over everything from football playoffs to presidential campaigns. As the three-day Martin Luther King Jr. Day holiday weekend began, the weather forecast was a crazy quilt of color-coded advisories, from an ice storm warning in Oregon to a blizzard warning in the northern Plains to high wind warnings in New Mexico.