This paper presents a system for mission planning for an autonomous underwater vehicle in time-varying ocean currents. The mission planning system is designed for the AUV "SLOCUM Glider" to collect oceanographic data along the Newfoundland and Labrador Shelf. The data will be used in conjunction with a numerical ocean model currently under development by the Department of Fisheries and Oceans Canada. This allows for the validation and the modification of existing ocean current and climate models as well as the design of new models with the aim of improving the accuracy of forecasts. The use of the ocean current forecast data in netCDF format in an ocean current model, the algorithms which consider glider-specific behaviour, details of the program's technical implementation in C++, and, preliminary results will be described.