Short-term supply planning is concerned with the anticipation of sharp deviations in actual customer demand, resulting in unseen loading of manufacturing plants, within the MPS planning horizon. A high level of accuracy in master production scheduling is normally achieved by effective collaboration of the production, distribution, sales and marketing functions of manufacturing industries. However, attempts to guarantee 100% on-time delivery, while maintaining minimum finished goods inventory, can create sharp fluctuations in near-term demand (especially in a volatile market environment) signals received by manufacturing plants.This paper presents a prototype supply planning system, which can be used to enhance the demand forecast within the MPS horizon, and addresses the difficulties with frequent re-scheduling and sharp fluctuations in near-term demand. The prototype combines expert system and decision support system technology in an integrated supply planners' workbench. The workbench functionality, technical specifications and architecture are presented, in addition to a discussion of the forecasting and rulesbase rationale.