This study examines mechanisms which control heavy snowfalls in the eastern coast of Korea. Previous observational studies have indicated that heavy snowfalls are caused by the advection of cold and dry air over the warm ocean off the eastern coast. Previous studies have not considered the effects of surface heat fluxes on heavy snowfalls. It is likely that the warm ocean produces strong surface heat fluxes that are able to invigorate convection and enhance precipitation. Motivated by this, this study examines not only the effect of the advection on heavy snowfalls but also that of surface heat fluxes and compare these two types of effects. In addition to this, this study looks into microphysical and dynamic processes which are associated with heavy snowfalls, considering that previous studies have not given us information on these processes. By running high-resolution simulations, this study finds that surface heat fluxes are a main driver of heavy snowfalls and the roles played by the advection in them are negligible. Surface heat fluxes induce strong updrafts and large deposition onto snow and cloud ice, which enables the efficient growth of snow and heavy snowfalls. This demonstrates that for better understanding of heavy snowfalls in the eastern coast of Korea, we have to better understand the surface processes that are linked to surface heat fluxes.