We got caught out at the river confluence as a serious storm rolled in from the West that carried a "confirmed large and deadly tornado." We stayed a bit too long and got caught in the downpour on our way out. We caught it on a point and shoot camera as we scurried out of the park, and you can clearly see the wall of water that made up the front of this crazy thing:
http://www.youtube.com/watch?v=pbwzOXdi45s