The bar is a little high on your back, the squats are shallow and your knees are getting too far forward.
Get the bar about it's diameter lower on your back.
Start the descent by breaking at the hips and knees at the same time and immediately get your chest aimed at the ground. Your knees are going to stop moving forward once the get to or just a little in front of your toes, they should get there by the time you are halfway down, and they stay there until you are halfway up (try using a TUBOW).
Remember the Master Cue and make sure you squeeze tight.