Is there any possibility he might have eaten something that didn't agree with him? Any extra people food, treats, or even some kind of plant in your house or yard? I know it's the weekend and you may not be able to find a vet, so until then, you can help him with the tummy troubles with pepcid and Tums, or Pepto Bismol tablets. Since he's going at both ends, hold off on his regular food and just feed plain cooked white rice for the next 24 hours. If the diarrhea and vomiting get better, add some canned white chicken to the rice and see how that goes down.
Keep an eye on his fluid intake during this time. If he isn't able to keep water down, you're looking at a more serious problem than a tummy upset, and run the risk of dehydration. If you don't already know the location of an emergency vet clinic near you, now would be a good time to do some research just in case you need to move quickly.
You should call your vet and get your dog in. Vomiting and diarrhea both are signs that there is something wrong and things can go down hill very quickly with dogs. Your dog could have a very serious condition, be poisoned, or any manner of things. Better to be safe than sorry - call the vet!