Abstract: A simple advection model is proposed for the prediction of precipitation patterns in complex terrain with arbitrary wind direction. The model includes the time delays associated with the conversion of cloud water to hydrometeors and the gravitational fallout of hydrometeors. The solution is evaluated using a Fast Fourier Transform. The model is tested against raingauge data from the central Alps and radar data from the Lago Maggiore area of northwestern Italy, for the heavy rainfall event on September 20, 1999.