To be honest, Jonti, I can't recall ever having a dream I mistook for an event while I was awake. But I have heard the hypothesis that prophetic dreams are those we remember when something happens in our lives that bring them to memory, where otherwise they would lie dormant in the recesses of our subconscious. That still doesn't discount the fact that we've had a dream of a future event.
My argument is that probabilities isn't an adequate explanation for such dreams. I understand the skeptic inclination to prefer mundane explanations over the supernatural, and I'm inclined in that direction myself. I just find myself frequently being skeptical of the skeptics because some of those mundane explanations don't seem anymore feasible than an appeal to the supernatural.