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Two Mesoscale Convective System (MCS) events that occurred in the southern portion of South America will be analyzed in order to characterize the local lightning activity related with different synoptic situations. On December 10-11, 2012, a MCS, originated by a cyclone centered over the Atlantic Ocean, presented an organized convective activity moving northeastward. This MCS formed in an area of baroclinic flow in the vanguard of a cold front. This feature was trivial in determining MCS displacement velocity, and consequently lightning density in the region. The other MCS that occurred on December 12-13, 2012 was generated by a low pressure area located in the central region of South America (Chaco Low), and showed disorganized convective activity moving (northwestward). This MCS formed due mainly thermodynamic factors in the lower troposphere and divergence in the upper troposphere by the interaction of the subtropical jet. In both MCSs lightning density in the region was influenced by the synoptic situation which the MCS was formed. Being influenced by the velocity and direction of MCS displacement. The rate of occurrence and polarity of lightning as well as the IC/CG and CG+/CG- rates were not affected by the different conditions that the MCSs were formed.The data set used in the present study will consider: (1) lightning location and polarity from BrasilDAT, (2) analysis and forecasts from WRF model, and (3) infrared channel data from Satellite GOES-12.