Abstract
A synoptic analysis is performed to identify the source and characteristics of an elevated layer of high airborne sulfate concentrations observed over southeast Wisconsin on 23–24 August 1976. The setting of the episode was the interaction of a weak, dry cold front with a slow moving weak anticyclone over the eastern United States. Although several explanations of the layer formation are possible, it appears likely that the layers form as the top of a deep mixed layer is lifted in a frontal zone and later become parts of subsidence inversions.
