The polar vortex will return, this time with the coldest temps of the year

It's coming back. The polar vortex — a deep mass of frigid air that rotates around the top of the world — has been knocked off balance, which means it's liable to spill cold air into the U.S. Although winter temperatures in the lower 48 states have generally been normal or warmer than average, a blast of intensely cold air first spilled down to the Midwest and the northeastern U.S. around January 20. Now, atmospheric scientists say it's likely to return at the end of January. For many places, that means it will be the coldest stretch of the year.  "It's going to get really cold at the end of January and early February," Jeff Weber, a meteorologist with the University Corporation for Atmospheric Research, an earth sciences research organization, said in an interview. Read more...More about Science, Polar Vortex, Extreme Weather, Science, and Climate Environment