We all wondered. Only Joe Bollinger of Glen Burnie asked: "What causes false returns or echoes on a radar screen?" NWS meteorologist Rick Winther blames temperature "inversions," often seen in fall or spring. That's when it gets colder at the surface than it is several thousand feet up. This temperature layering can "trap" some radar energy, bouncing it back toward tall "ground clutter" such as mountains and buildings. That returns nonweather echoes to radar screens.