Five partial balloon soundings of electric field and thermodynamics were made in a mesoscale convective system (MCS) in 1998. Data were gathered in an updraft and outside updrafts within the convective region, in the transition zone, and in the stratiform cloud region. In the first sounding the maximum and average inferred updraft speeds (27 and 15 m s-1) are the largest found to date in soundings through MCS convection. As in previous measurements the electric field profile is simpler and fewer charge regions are inferred within the updraft than elsewhere. Together the first four soundings support in most details a previously published conceptual model of MCS electrical structure from the convective region updraft to the transition zone. Two exceptions within the soundings were found; these involve opposite polarity of the lowest two charge regions in the transition zone cloud and additional complexity above the main negative charge region. The earlier conceptual model also showed possible connections between charge regions across an MCS, but those were based on soundings through many different MCSs. The first four soundings presented herein provide stronger evidence for three to five similar charge regions across the front of this MCS. The sounding through the stratiform cloud region was atypical and does not fit the conceptual model, and no connections to charge regions in the rest of the MCS are obvious. Two soundings presented from a second MCS indicate that the upper three charge regions in the transition zone are connected to the stratiform cloud, as depicted in earlier conceptual models. ¿ 2001 American Geophysical Union