Remember that time when a giant pattern of Arctic air descended over the U.S. and Canada, freezing everything in its path? Remember when it came back? Yeah, that's all happening again.

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:

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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:

NOAA/CPC

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: