Snow accretion on electrical wires occurs because of the adhesive force between the snow crystal and the wire surface. Severe snow accretion can not only cause the collapse of transmission towers but also induce self-excited oscillations, known as galloping. Galloping can result in line collision and subsequent short circuit. Thus, snow accretion poses a significant threat to electric infrastructure. To better understand and predict such phenomena, various numerical simulations of snow accretion have been proposed. Eguchi et al. conducted simulations using a grid-based method and achieved qualitative agreement with experimental results. However, they were unable to reproduce the surface roughness of the accreted snow. To address this issue, Shimura et al. performed simulations using a particle-based method and obtained good agreement with experimental results in terms of snow accretion height, but their model did not consider the motion of the accreted snow body. In this study, we introduced a sliding motion for the accreted snow body based on the shear adhesion stress of snow and conducted long-term simulations using an existing particle-based snow accretion model. Specifically, we introduced a simplified sliding model in which the snow body begins to rotate when the torque due to its weight exceeds the maximum adhesive torque calculated from the shear adhesion stress. To investigate the aerodynamic effects of the accreted snow body, the surrounding flow field was simulated using a grid-based method. An overset grid was constructed based on the snow geometry obtained from the particle-based method. The flow field was assumed to be two-dimensional incompressible turbulent flow, and unsteady simulations were performed. The simulation results revealed a significant increase in snow accretion due to the expansion of the projected area in the particle injection direction following the onset of sliding. In a one-hour simulation, the projected area in the no-sliding case was 0.029 m², nearly identical to the wire’s projected area of 0.028 m². In contrast, when sliding occurred, the projected area expanded to 0.044 m². As a result, by the end of the simulation, the accreted snow mass increased from 0.48 kg/m in the no-sliding case to 0.64 kg/m in the sliding case, representing a 33% increase. Furthermore, changes in the accreted snow shape altered the aerodynamic characteristics of the wire, leading to greater fluctuations in both lift and drag forces.