This study investigates the predicted motion of small, light particles using the stochastic separated flow models proposed by Shuen et al. (1983) and Lightstone and Raithby (1998). Model predictions are compared to the benchmark experiment of Snyder and Lumley (1971) for particles released from a point source in grid-generated turbulence. It is found that the predictions of particle velocity variance and dispersion exhibit nonphysical waves. This behavior is explored in order to understand its mathematical basis arising from the model formulation. A modification to the model is presented. The modified model is successful in removing the characteristic waves.