http://admission.universityofcalifornia.edu/counselors/transfer/index.html says that “A transfer applicant is a student who has enrolled in a regular session at a college or university after high school. Students who meet this definition cannot disregard their college records and apply as freshmen.”
So your chances are 0% at at UCs until you get to where you will earn 60 semester units of college work before transfer as a junior (and high school GPA and SAT scores do not matter). Most transfer students to UCs come from California community colleges.
Stanford admits very few transfers; based on its announcements welcoming incoming students, it tends to favor non-traditional students for transfers. For example: https://news.stanford.edu/2017/11/01/small-mighty-cohort-transfer-students-joins-stanford-community/