Measurements of the ratio of oxygen-18 to oxygen-16 are often used to reconstruct past climate or to quantify phase changes. However, in most models, the evolution of the isotopic ratio is calculated using the Rayleigh parameterization. The Descam model has recently been extended to simulate isotopic fractionation from occurring condensation/evaporation processes and the mass of oxygen-18 in aerosol particles, droplets, and ice crystals explicitly as a function of their size. In a first step, isotopic calculations are implemented into the 1.5D dynamical framework where several sensitivity studies are conducted to test the evolution of the isotopic ratio as a function of the different phase changes in a convective cloud. Though an isotopic signature can be identified for different microphysical pathways, the predominant factor for the isotopic ratio in the precipitation seems to be the dynamical evolution of the considered cloud.