In power system studies, seasonal load duration curve (LDC) plays an important role in medium term horizon power system planning, reliability and energy markets studies and economic analysis of electric power systems. Therefore finding a simple and accurate model to forecast LDC is beneficial to network operators as well as market participants. This paper proposes a new framework to forecast seasonal LDC. As there are few contributions regarding forecasting curve time series, we redefine the problem of forecasting LDCs into a vector forecasting problem. In fact, we divide LDCs into three parts and then, artificial neural network (ANN) engines are used to forecast future values of the three parts. The load data of Alberta electricity market from 2000 to 2013 is used to verify validity of the proposed method