With the emphasis on renewable energy integration, stochastic methods have begun to emerge as one of the most viable alternatives to traditional deterministic planning. The value of stochastic planning lies in its effectiveness at reducing operational costs, while allowing higher penetration levels of renewable sources, and without much sacrifice to system security. This is under the premise that the decision maker may not need to fully hedge against more extreme and costlier events that exhibit lower probabilities of occurrence. On the other hand, stochastic methods do suffer from the curse of dimensionality, which renders them computationally intractable for practical application. Here, we propose a new stochastic approach based on the flexibility envelopes concept. It circumvents the curse of dimensionality by using probability-weighted envelopes to enclose the evolution of the net load uncertainty over a planning horizon. The new approach is illustrated by an extensive receding-horizon economic dispatch example to compare its effectiveness to the earlier deterministic version that used a single envelope.