on Jane Friedman site:

Imagine Vermeer’s Girl with a Pearl Earring in a brightly illuminated studio, or anything Goya ever painted rendered in blazing strokes of Thomas Kinkaid-style light.

In story as in art, what’s hinted at in the shadows can add intriguing layers of depth and interest.

Foreshadowing is a literary device in which future developments in a story are hinted at before they happen, presaging what’s to come. It adds dimension to stories just as shading and shadow add it to visual images: Foreshadowing can heighten suspense and tension, increase momentum, raise a story’s stakes, deepen and develop characters, and pave in key plot developments to give the story more cohesion.

But just as in visual art, the finesse of foreshadowing is in how and where you direct the reader’s attention: How much you use, where, and what effect it creates in the story. The artist achieves those results using dark and light tones. Authors have a similar palette to work with: various shades of direct and indirect foreshadowing.