Blasts of frigid air will plunge into the northern Plains, Midwest and eastern U.S. Some of this air might be the coldest in late December in at least 20 years. Increasing odds of significant winter storminess in the eastern half of nation between Wednesday and Christmas Eve. The core of the cold will probably remain over the north central United States through midweek. A second, reinforcing blast of cold may dive into the northern Plains and Upper Midwest. Temperatures 10 to 20 degrees below normal could reach parts of the South and eastern U.S. late in the workweek.
