The tornado that struck Troy, Alabama, on Thursday night was an EF-1 with estimated winds of around 100 MPH, according to the National Weather Service. The tornado produced “extensive damage” to a Walmart and Hibbett Sports, injuring six people. The NWS did not issue a tornado warning ahead of the storm.

A possible tornado struck Troy, Alabama, without warning on Thursday night, damaging several structures and overturning a tractor trailer along its path. Early reports on Twitter indicate that the local Walmart and a sports store sustained heavy damage, with the roofs of both stores caved in, much to the surprise of the dazed shoppers inside.

Over the past twelve years, we've seen tens of thousands of tornado warnings across the United States. Almost every major city east of the Rocky Mountains has seen a tornado warning at some point since 2002, and the resulting maps are pretty cool looking.

In an ever-growing effort to provide valuable weather information — or just a vulgar display of automated GIS skills — the National Weather Service is tweeting out images that show how many people are impacted by severe weather. The exercise shows just how little of the United States is populated.