In ADPIC, the deposition emerging from washout has thus far been modelled rather crudely, since the only option has been to turn the rain on and off at different times. This kind of modelling is particularly unsatisfactory when ADPIC is used to model continuous releases over long periods of time. The assumption of simultaneous rain throughout such a large plume is simply not true. In this report a modified version of ADPIC with a three-dimensional (3-D) washout coefficient is presented. The effect of space variable precipitation is examined via two separate releases that are simulated for a period of 48 hours: one continuous {open_quote}Chernobyl-like source{close_quote} release and one instantaneous {open_quote}nuclear explosion-like{close_quote}. Simulations with both the new and old formulation are made and the resulting deposition patterns are compared.