If you happened to check the weather radar out of Aberdeen, South Dakota before sunrise last Wednesday (who didn't?), you saw an incredible and unusual sight: a small, spiraling cyclone of snow racing southeast. The swirl almost looks like a small tropical cyclone, with an eye and everything. Here's a look at how the impressive feature formed.

A strengthening low pressure system in western South Dakota is the source of a major blizzard that's expected to ramp up over the northern Plains today and tomorrow, bringing with it the potential for up to two feet of snow, wind gusts of 60 MPH, and cause temperatures to plummet into the single digits with wind chills as low as 15 degrees below zero.