foretell, predict, forecast, prophesy, prognosticate mean to tell beforehand.

foretell applies to the telling of the coming of a future event by any procedure or any source of information.

predict commonly implies inference from facts or accepted laws of nature.

forecast adds the implication of anticipating eventualities and differs from predict in being usually concerned with probabilities rather than certainties.

prophesy connotes inspired or mystic knowledge of the future especially as the fulfilling of divine threats or promises.

prognosticate is used less often than the other words; it may suggest learned or skilled interpretation, but more often it is simply a colorful substitute for predict or prophesy.