Two meso-scale numerical models, the Advanced Regional Prediction System ARPS, and a model based on the computational fluid dynamics model CFX-4, were used to simulate very high resolution wind fields above the complex mountainous topography of an Alpine ridge. Using an horizontal mesh resolution of 25×25 m, both models were able to reproduce qualitatively important flow features (change in direction and separation) that had been observed in the field. However, it could also be shown that the boundary conditions strongly influence the results.