he Year of Polar Prediction (YOPP) is focused on a number of Special Observing Periods (SOPs) of two to three months’ duration in both the Northern and Southern Hemispheres. One feature of the SOPs is a program of enhanced radiosonde and buoy measurements contributing to assessments of how the extra observations support improved forecast skills. Another activity resulting from the SOPs is the YOPP Supersite Model Intercomparison Project (YOPPsiteMIP). The YOPPsiteMIP concept is unique compared to Climate Model Intercomparison Projects (CMIPs) because of (1) a focus on Numerical Weather Prediction (NWP) scales, processes and improvements, (2) the selection of polar, intensive, surface observing locations (YOPP Supersites) for which the NWP centers will create high-resolution model outputs and (3) special merged, observation outputs for the YOPP Supersites matched to the model outputs. These unique datasets of matched model time-step output and multi-variate high-frequency observations will enable detailed analysis of fast, small-scale processes. Example processes of interest are coupling mechanisms between the atmosphere, ocean, land and ice; cloud/precipitation micro- and macro-physics; the energy budgets over land, ocean and ice; and structure of the planetary boundary layer and the ocean mixed layer. The YOPPsiteMIP planning has focused so far on Arctic terrestrial YOPP Supersites, however, discussions are initiated on expanding the concept to selected Antarctic sites, as well as to ships and ice-stations in the Arctic Ocean. Preliminary results of the observation-model process-based evaluations at the YOPP Supersites relevant to environmental predictions ranging from weather to S2S scales will be presented.