First of all, when Pearl asks Dimmensdale to acknowledge her publically, he refuses and a meteor forms a dull letter "A" in the sky.
Second, when the three embrace they begin making plans. The foreshadowing there is the four day mark which makes the reader's clock tick, sort of figuring that Chillingworth will get in between. In fact, that is the case.
Before that, Hester took off her letter, and there was a moment of peace in the action from the three main characters. This was a foreshadowing of the "eye of the storm" that is about to happen once Chillingworth comes back to destroy them.
The release from Dimmensdale is also a sign of his impending death.
The last chapters of the novel foreshadow how the novel will end. In Chapter 20, Dimmesdale is confronted by Mistress Hibbins, then Chillingworth. Mistress Hibbins lets him know his decision to run away from his sin will cost him his soul. “But at midnight, and in the forest, we shall have other talk together. “ Later, when he is talking to Chillingworth, Dimmesdale says, “I hardly think to tarry with my flock through the fitting seasons of another year,” foreshadowing his death at the end of the novel. In Chapter 22, Hester watches Dimmesdale take in the procession. As she watches, she feels “…a dreary influence come over her.” This foreshadows the unhappy ending of the novel.
Mistress Hibbins is also an example of foreshadowing. People view her as a “witch;” therefore they avoid her at all costs. She speaks to Hester, asking her questions about her time in the forest with Reverend Dimmesdale. Hester is taken aback because she thought no one saw her with the Reverend in the forest. Mistress Hibbins says, “…he (the Black Man) hath a way of ordering matters so that the mark shall be disclosed in open daylight to all the world.” This foreshadows Dimmesdale’s revelation of his sin on the scaffold in front of the entire community.
In Chapter 21, the author is describing Hester and Pearl as they attend the holiday. Pearl is, of course, wearing finery sewn by her mother. However, Pearl shows that she is aware today is not just any day. “On this eventful day, there was a singular inquietude and excitement in her mood.” Pearl foreshadows the dark end of the novel in Chapter 22 when she sees the minister and asks, “Else I would have run to him, and bid him kiss me now, before all the people…” Pearl’s words show the reader that in the end, Dimmesdale must accept her openly and admit his sin.