We investigate the global evolution of the viscous stage of a turbulent protoplanetary disk. The time-dependent radial development of the nebula is calculated with the help of analytical one-zone models of the vertical structure that relate optical properties of grains to turbulent viscosity. Special attention is given to possible growth of dust particles that cause significant opacity and hence viscosity changes. In the framework of a simple two component model for the dust size population we follow the evolution of the total surface density of the disk. Assuming that grain growth is especially rapid in the main condensation regions (e.g. due to enhanced sticking probabilities) we find significant surface density enhancements in these radi...