 We have developed and deployed a 3D interferometer type lightning mapping array in LMA for observing winter lightning in Japan. This array consists of three broadband interferometers installed at three stations with a distance of three to five kilometers apart. Three disc one antennas are installed at each interferometer station, forming a right triangle with a separation of 75 meters between them. The output of each antenna is filtered down to 400 megahertz and recorded at one gigabit per second with 16 bits of accuracy. A new method has been proposed for solving the 3D problem of a lightning mapping system consisting of multiple interferometers. Using this system, we have successfully mapped a positive cloud to ground, CG, lightning flash in winter, focusing on its preliminary breakdown, PB process. By studying the individual PB pulse processes, it appears that these smaller scale discharges are scattered over a height range of approximately 150 meters. These smaller scale discharges appear to be continuous in space, but discontinuous in time. Additionally, we have examined the positive return stroke in the