My longest run is a weekly 10 miles. And weekly milage is around 30-35 mpw. I'm a hobby jogger.
Usually I run my 10 miles long run pretty easy, around 9 min/miles, but if I focus I think I can run it in 8:30/miles without being drained out.
The half marathon is 3 miles longer, do you think it's possible for me to run a half marathon race in 8:15/mile pace given the parameters I laid out ?