Here's Wunderground's Jeff Masters, who completely buried the lede with something about a "major February thaw" across the Midwest U.S. before delving into this forecast of horrors:
Fortunately (?) for the Midwest, this week's thaw will be short-lived, preventing the kind of major flooding that would result if all of the snowpack were to melt in a week. This morning's runs of the GFS and European models were better able to handle the evolving upper-air pattern over the Pacific Ocean, and it appears that their earlier runs seriously underestimated the strength of a ridge of high pressure forecast to build over the Western U.S. 6 - 10 days from now. This ridge will be accompanied by a return of the cold "Polar Vortex" over the Midwest and Northeast U.S., bringing bitter cold temperatures and strong winds. Temperatures 20°F below normal will likely invade the Upper Midwest on Sunday, and gradually spread southeastwards during the week. The peak cold is predicted to occur late next week, with temperatures 20 - 35° below normal covering much of the eastern 2/3 of the country.
To reiterate, that's temperatures 20 to 35 degrees below normal. Over much of the easter two-thirds of the country. We have six to ten days to prepare.
Here's what it'll look like:
Sure, we were cold the last two times around. But did we truly appreciate the might and force of the original polar vortex? This mind-blowing NASA video demonstrates just what we were dealing with: