What are my chances of being accepted to transfer into Top 20 universities?

Pitt offers everything that a student needs to get into medical school. It sounds like you are seeking prestige. That will be obvious to top 20 schools and most will not consider that a valid reason to transfer.

Also you are from Philadelphia nd you are considering UChicago? You want to be closer to home and have the weather that you enjoy? You are grasping for reasons to transfer.

@TomSrOfBoston I wanted to apply to UChicago since I visited and I liked it but I was already applying to a lot of other colleges so I didn’t apply for freshman year and now I regret it. Also, flying to UChicago would take less time than driving to Pitt (driving since flying is only 1.5 hr).