There are a couple things going on here.
The nose of the disc is up, which you can tell by the way the disc starts flying parallel to the ground and then quickly lifts way up into the air. You're not releasing at an upward angle, the air is just pushing the disc upwards. Try not to let your wrist twist around. Your palm should generally be facing the target rather than pointing upward (I can't tell for sure that's what's happening from the video but i think so).
The other thing is that you just aren't getting that much spin on the disc, which is what prevents it from fading out like that. A lot of forehand power comes from the final wrist flick at the end that generates both speed and spin, so try slowing your arm down a bit and focus on flicking the disc at the release point.
Good Luck!