The relative roles of direct insolation and near-surface moisture advection in the recovery of convective available potential energy (CAPE) on 31 March 2016 in northern Alabama are examined using VORTEX-Southeast observations and numerical simulations. In between rounds of nontornadic morning storms and tornadic evening storms, CAPE over the VORTEX-Southeast domain increased from near zero to at least 500 J kg-1. A timeline of the day's events is provided with a focus on the evolution of the lower levels of the atmosphere. In particular, we focus on its responses to solar insolation and moisture advection, which are hypothesized as the main mechanisms behind the recovery of CAPE. Data from the University of Massachusetts S-Band frequency-modulated, continuous-wave (FMCW) radar and NOAA National Severe Storms Laboratory (NSSL) Collaborative Lower Atmospheric Mobile Profiling System (CLAMPS) are used to characterize the boundary layer evolution in the pretornadic storm environment. It is found that insolation-driven diabatic heating was the primary driver of rapid CAPE recovery on this day.