Atmospheric soundings observed on the windward side of the Medicine Bow Range (Wyoming) during a leeside BLS event are used as the upstream forcing for several idealized simulations. Results show that LES can capture the essential features of BLS as known from in-situ and remote observations. The most distinctive elements of the flow field are a breaking hydrostatic wave at upper levels and strong, pulsating katabatic flow near the surface. The latter detaches from the ground upstream of a recirculation region, where highly non-stationary rotor and sub-rotor vortices occur. Results show the sensitivity of the rotor dynamics to increasing surface friction, which enhances flow deceleration on the lee of the obstacle and shifts the separation point upstream. The amplitude of wavelike motions downstream of the ridge also decreases with increasing friction, leading to less intense rotor circulations.