In this article, we present the results of our study of knowledge in the actor-network of snow avalanche forecasters and observers in Longyearbyen, Svalbard. Our study aimed to understand how observers and forecasters make sense of snow conditions and snow avalanche risks. To do so, we conducted empirical investigations, which included interviews with key observation, forecasting, and decision-making actors in Longyearbyen’s risk governance system and autoethnographic participatory observation by the first author during the 36 months they worked closely with several informants in Longyearbyen. We draw on perspectives from literature on sensemaking, sensework, and tacit knowledge to conceptualize the modus operandi of observers and forecasters in a manner that allows for generalization to contexts beyond snow avalanche forecasting in Longyearbyen. We find that avalanche-related knowledge construction is highly dependent on the experiences of the observers from their non-professional interaction with the local topography and snow as part of their leisurely activities. Further, social relations and communication among observers and forecasters are essential in knowledge construction. Based on the different processes and resources entering the knowledge construction, we describe three dimensions of local knowledge involved in snow avalanche forecasting: situated, social knowledge; embodied knowledge; and synthetic knowledge. We elaborate on these dimensions of knowledge and discuss implications for the development and administration of avalanche warning systems in contexts characterized by a high degree of transience and change in phenomena.