What are examples of foreshadowing in Romeo and Juliet, specifically act 1 scenes 1-5? Could you explain why?
First of all, this is outside the scenes, but the prologue is a huge part of the foreshadowing.
From ancient grudge break to new mutiny,
Where civil blood makes civil hands unclean.
This is saying that their "ancient grudge" creates new problems (as in, Tybalt killing Mercutio, Romeo killing Tybalt, Romeo and Juliet dying, etc.) I believe that could be considered the 'new mutiny'.
From forth the fatal loins of these two foes
A pair of star-cross'd lovers take their life;
Essentially saying that the only pair of 'star-cross'd lovers' in the play, Romeo and Juliet, kill themselves.
Whose misadventured piteous overthrows
Do with their death bury their parents' strife.
With their suicide, Romeo and Juliet 'bury their parents' strife' -- they put an end to that 'ancient grudge'.
Another very important monologue that foreshadows the events of the play is Romeo's speech at the end of 1.4 when he and his buddies are heading to the Capulet party.
I fear, too early: for my mind misgives
Some consequence yet hanging in the stars
Shall bitterly begin his fearful date
With this night's revels and expire the term
Of a despised life closed in my breast
By some vile forfeit of untimely death.
But He, that hath the steerage of my course,
Direct my sail! On, lusty gentlemen.
This speech is basically Romeo saying, "I don't feel too good about trespassing into this party. I have a bad feeling that this will begin some fearful event that will possibly end in death." And then, possibly seeing his friends in their good mood, he says, "But, whatever. I'm sure things'll be fine. Let's go!"
Did that help?