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A case study was done for the 15 May 1986 severe thunder-storm and tornado mini-outbreak over southwest Indiana. Storm types and environmental conditions were analyzed to check for predictability with current severe storm knowledge and conceptual ideas. Environmental conditions preceding and during the severe weather outbreak were investigated with soundings and hodographs. A radar analysis exposed reflecti-vity notches, hooks and bows associated with some of the storms. Environmental conditions were found to destabilize as after-noon Convective Available Potential Energy (CAPE). B +. increased sign!ficantly. This helped to offset decreases in storm relative helicity which occurred during the afternoon. An old thunderstorm outflow boundary from a mesoscale convective system (MCS) provided a source of baroclinically generated horizontal vorticity as thunderstorm inflow was tilted upward by the updrafts producing mesocirculations. Both classic and high precipitation (HP) supercell storm types produced the severe weather over southwest Indiana. Rear inflow notches (RINs), weak echo notches (WINs) and hooks were common storm features observed. 1