My son's UCL tear was described as long term and progressive. He never felt a pop. But in the last week of the summer he did experience a significant velo drop that got worse every outing, and then eventually mild pain while throwing.
Ditto all the advice above, plus this - despite all you hear about it within the baseball community, TJ is actually a fairly rare procedure in the overall population. Paraphrasing what Dr. Cain told us, the UCL's only purpose is for throwing a baseball, so UCL tears are rare outside of baseball. And if you aren't a baseball player, there's usually no need to have it surgically repaired if it does tear.
Consequently, most local ortho surgeons don't do the surgery. If you have a UCL tear and want to continue your baseball career after high school, you need to go to a surgeon experienced with college and professional pitchers. It's probably going to require some travel.
Do your homework on surgeons. We were fortunate enough to have a travel ball pitching coach who was an ex-Major Leaguer that had the surgery and made it back to the show. He directed us to Dr. Cain in Birmingham, even though that is 3 hours away. If you don't have such a resource at your disposal, call the trainer at your nearest MLB team or major college to see who they would recommend.