Can I appeal to UC admission with my first semester senior grade?

This semester senior year, Im taking 5 AP and got one B and rest A. It is the farthest my best grade in my high school years. SO I really want them to see it and see the progress I made over the years…Will UC see my first-semester grade in the admission process? Or will they see after the admission process?

UC’s do not ask for 1st semester senior grades unless you receive a request for a supplemental review. They will only see your Senior grades on your HS transcript after you are admitted and enrolled. You however need to update each campus if you receive a grade below a C or change Senior classes.

They expect you to maintain your competitive academics throughout Senior year.

I think what you are asking about is whether UCLA considers application updates, information available after the application was submitted but before decisions are announced. An appeal is only made after admission is denied.

They do not accept admission updates, unless they ask for them as @Gumbymom mentioned. Furthermore students that are denied cannot submit their final transcript and ask to be reconsidered because their gpa has improved. They say

High grades received in the senior year, recently acquired awards or additional extracurricular activities are not a basis for the reversal of a decision since decisions are based on academic information that was available at the time of application.
https://admission.ucla.edu/apply/freshman/freshman-applicant-appeals