Powder snow avalanches are a common hazard in high alpine regions. Steep tracks and cold snow temperatures facilitate the formation of the powder suspension cloud developing from the dense, fast-moving avalanche core. Considerable damage to buildings and power lines is possible even when the dense core of the avalanche stops before reaching the infrastructure. An efficient simulation tool that calculates powder pressures in three-dimensional terrain would help engineers plan mitigation measures. We present a novel two-layer powder avalanche model that couples the cloud to the flowing core, allowing the simulation of mixed flowing/powder avalanches. The model predicts endangered areas outside the reach of the dense core. We apply this model to a well-documented case study in southern Switzerland and discuss the potential for future engineering applications.