Performance prediction is valuable in different areas of computing. The popularity of lease-based access to high performance computing resources particularly benefits from accurate performance prediction. Most contemporary processors are employing multiple computing cores, which complicates the task of performance prediction. In this paper, we describe the methodology employed for predicting the performance of a popular weather forecasting application on systems with between 4 and 256 processors. An average prediction error of less than 10% was achieved after testing on three different multi-node, multicore systems.