Flash flooding is one of the most destructive atmospheric phenomena, made more dangerous by how difficult it can be to predict. Equations that aid forecasters by efficiently combining several atmospheric variables have been created for a number of other dangerous weather hazards, but never for flash flooding. Parameters calculated from single-point soundings were weighted by their empirical ability to differentiate flash flooding proximity sounding environments from control environments, and were synthesized into a single equation called the Flash Flood Parameter (FFP). The discriminative ability of the index was demonstrated by a high degree of success at differentiating flash flood soundings from control soundings across a range of atmospheric conditions. This work can be combined with non-atmospheric understanding of flash flood development for use in operational forecasting, and can likely be synthesized in long-range seasonal and climate models to approximate patterns favorable for flash floods.