A mesoscale model is used to study the 3-dimensional turbulence structure of the stable atmospheric boundary layer. We compare modeling results with aircraft observations in the vicinity of Cape Mendocino from the Coastal Waves 96 field program. The aim in this study is to reproduce the important physical processes, such as local forcing from coastal topography. The persistent northerly or northwesterly winds during summertime bring marine air over cool upwelling coastal waters, resulting in the formation of a stable internal boundary layer (IBL). Strong wind shear gives rise to turbulence, which is largely confined to the IBL. Far offshore and upstream of the cape observed turbulence within the IBL scale convincingly with local similarity scaling. Downstream from the cape, where the flow accelerates and forms an expansion fan, this scaling breaks down. The numerical experiments are set up to match observed conditions upstream of Cape Mendocino in order to investigate processes responsible for the break down of the scaling near and within the expansion fan. We also investigate possible reasons for the apparent differences between measured fluxes in the surface layer and simulated bulk fluxes. Observations are presented in a companion paper.