After you toggle Overlay2(on) and you start stepping through a sequence of soundings, the previously viewed sounding's Skew-T temperature, dewpoint, winds, and hodograph trace is colored green. "Overlay2" displays only two Active soundings, while the compare buttons, "CompStn" and "CompTm", displays multiple Active soundings. The compare buttons are automatically disabled when the Overlay2 button is turned on, and the Overlay2 button is automatically disabled when the compare buttons are turned on.
KBMX 18Z Skew-T with the previously displayed KBMX 12Z Skew-T overlayed in green. The previously displayed Skew-T can come from a different time or station.
Hodograph with the previous hodograph trace overlayed in green. The previously displayed hodograph trace can come from a different time or station.