On 132 near Vernalis, heading west (about 2pm) I noticed what looked like a funnel cloud above the ground to the left on the other side of the river. It was wider than the ones we've seen before near Turlock so I kept staring at it to try to figure out if it was just the way the clouds were arranged or a real funnel. It was quite well defined and came about half way down from the sky. There were huge lightning bolts all around it. I kept driving and trying to watch it at the same time, then it sort of grayed out and there was a tremendous downpour of rain mixed with hail (not big enough to dent the car) I was worried that it could be a real tornado approaching, so I just continued driving, but the fastest any of us on the road could go was 40mph since the visability was almost zero and there was so much water on the road- and the hail pellets hitting the car was really distracting. Finally after driving awhile, the rain stopped and I reached blue sky again. When I looked behind me, the sky was completely black. I decided to turn around and go back to the Old Fisherman's club so that I could observe if there was a tornado going on, but it was too scarey to stay parked there with all the thunder and lightning so I decided to take off. When I got to the part of the highway that turns off towards Stockton, the traffic stopped due to a terrible accident that must have happened about an hour earlier. There were overturned cars on the side of the road and car parts scattered all over. They were finishing the road clean-up as I drove by.