http://www.newsweek.com/polar-vortex-winter-weather-storms-explained-nws-forecast-1568649

Extreme winter weather is predicted to expand into multiple states this weekend as a "polar vortex" causes snow, ice and freezing rain.

Arctic high pressure pushing south from Canada will result in "frigid temperatures" to the U.S. midsection from Friday to early next week, in some cases more than 40 degrees below average temperatures, according to the National Weather Service (NWS).