In February of 1982 the SOUSY-VHF-Radar, located near Hannover, West Germany was operated during the passage of a warm front. The timing of the radiosonde ascent from nearby Hannover was such that the narrow frontal zone boundary was immediately overhead at a height of approximately 7 km. The data from this event has made it possible to make a detailed comparison of the radar and radiosonde reflectivity data that has not been possible before. We find that the frontal boundary that is detected by the radar appears as a very low tropopause height in the radiosonde data (approximately 3 km less than the mean during this time.