precursor
noun[L. proecursor, supra.]
A forerunner; a harbinger; he or that which precedes an event and indicates its approach; as Jove’s lightnings, the precursors of thunder. A cloud in the southwest, in winter, is often the precursor of a snow storm. A hazy atmosphere in the west, at sunset, is often the precursor of a cloudy or of a rainy day. Evil thoughts are the invisible, airy precursors of all the storms and tempests of the soul.