This chapter introduces state-of-the-art and present developments in short-term forecasting approaches, with a focus on specific applications in the operation of insular power systems. The chapter describes the general information sources used for short-term forecast, including numerical weather prediction (NWP) and wave forecast systems. An introduction to forecast techniques used in the scope of SiNGULAR is presented to understand the tools used in the forecast model application. Because of the specific requirements of insular systems, probabilistic forecast tools will be adopted. Forecast models will be presented for application in wind power generation, photovoltaic (PV) solar generation, hydropower generation, and load prediction using some practical examples. Benefits of providing geographical aggregated forecasts are also shown, with special attention to wind power. Finally, the forecast system interface and its usage in a specific scheduling methodology developed within the scope of the SiNGULAR project is analyzed. © 2015 by Taylor & Francis Group, LLC.