Attack!

While enjoying a peaceful lunch outside I felt something crawling on my leg.  I jerked and threw salad, book and chair in my attempt to get away from the creature when I saw what it was.  I was up and ten feet away from the scene in less than a second.  I think it's possible I flew.  

Naturally I was curious so I came back over and introduced myself.    

I spent the next 30 minutes carefully watching this critter as it produced thread and wadded it carefully, every so often making a plunge towards the ground.  I can only assume the plunge created the thread and the spider then used the thread for further wadding. 

But what the wads are for I don't know.

A coworker thought that this might be a spotted orb weaver.  What do you think?