The synchronization of metacommunities due to dispersal among patches is analyzed in the case of slow-fast populations. The analysis is performed by studying a standard model with the fast population dispersing when special meteorological conditions are present. This assumption fits very well with the peculiar nature of slow-fast systems and implies that metacommunities synchronize if the slow population accelerates during the outbreak of the fast population. This result shows great  potential in the study of marine and fresh-water plankton communities as well as in the study of synchronization of insect-pest outbreaks in forests.