The weak line of reflectivity ahead of the storms is the gust front.  This feature had outrun the line of storms by 5 to 10 miles and led to the roll cloud in Hamilton County.  This line of storms produced widespread severe weather across Indiana but weakened by the time it got to southwest Ohio.  Many times (but not always) when a gust front outruns a line of storms like this, it is a sign the storm is losing its potential to produce severe damaging winds.