Cloud-to-Ground (CG) lightning flashes produced during IOP 2a are analyzed and associated to physical characteristics of the convective storm system developed over the Lago Maggiore Target Area (LMTA). IOP 2a was the most electrically active during the MAP-SOP since it represents 75 % of the total CG activity measured over the LMTA during the whole SOP. Thundercells were strongly vertically developed (sometimes more than 12 km of height) and produced large amounts of rainfall and some hail. Some of them exhibited exceptional CG rates at 12 per minute. Radar data allow us to retrieve the 3-D wind and radar reflectivity fields (from two synchronous Doppler radar) and particle types fields in the thundercells (from the S_Pol polarimetric radar). Both polarities of CGs are distinguished in this study. We first consider temporal and spatial correlation from the global activity over the LMTA and for some individual cells. We observe very strong correlation between CGs and the presence of Graupel-Hail mixture, what is in good confidence with the non inductive charging mechanism. CGs seem to be located at the vertical of large radar reflectivity values and located around the maximum vertical velocities. Thundercells exhibit different electrical behaviors : Most of them mainly produced negative CGs but some others produced a lot of positive CGs. In order to better analyze this difference, we particularly study two individual cells : the first one mainly produced negative CGs, and the second one produced 64% of positive CGs in the second phase of its lifetime. We observe low CG rates associated to the presence of hail in the thundercell. Large positive CG proportions are associated to severe weather, especially the presence of hail and strong vertical velocities.