The largest hailstone ever recorded in America spent close to an hour aloft in a cloud growing to the size of a small volleyball, then plunged to earth at more than 100 mph, struck the ground in South Dakota weighing nearly 2 pounds, left a divot, was scooped up by a local rancher and placed in a freezer, melted a bit during a power outage, was packed in dry ice and driven cross country, and finally arrived at a lab in Boulder where Charles Knight, one of the nation’s premier authorities on hail, added it to a research collection that also included the two previous record-setting hailstones. Even by Knight’s high standards, though, the golf ball-sized hail that hammered the western metro area last week was something to behold. “Large hail is pretty rare this close to the Front Range,” said Knight, a senior scientist at the National Center for Atmospheric Research.