when i am playing a descending picking run near the 12 frets on the high e, b, and g string, my third finger keeps going flat on the string and not staying on the tip of my finger, how can i fix this

I'm sorry to bump in, but Kris's anwser might take a while since he's always very busy! I think the best thing to do for you is play those runs very slowly, watching your finger. Use a metronome to speed up gradualy, and at the speed where you're finger is just not going flat again, keep practicing, then try 5bpm higher, and so on. Also, you might want to train the third finger strength, by doing lots of hammer ons!

Sounds like you are pushing speed, as a test - could you try and play it half the speed (extremely slow) and see if you get better control of you finger?

If that is the case then I would suggest doing a simple six note exercise which just focuses on getting control of that finger!

thanks guys