Do you actually understand what the word "omniscience" mean? Because you talk about it as if it were no more than mere prophetic foresight. (If one were to accept at face value the notion that God exists outside of time than the distinction between past, present, and future is mere orthographical jerking-around anyway).
Omniscience is the knowledge of all that which is knowable. If an omnipotent and omniscient being were to consider doing X, he would be infinitely aware of the consequences of doing X. And of not doing X. And of doing X but not Y, Y but not X, both X and Y or neither. It's not so hard to understand.
Because it is logically impossible. And how can something exist that is logically impossible, hm?
Here's a good demonstration of why infinite regress is fallacious:
"A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist gave a superior smile before replying, "What is the tortoise standing on?" "You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!"
Now, how in the world can an infinite chain of turtles be standing atop one another, hmm? Somewhere at the bottom of the chain there must be a turtle on which all other turtles are standing and which is not, itself, standing on a turtle. Understand?
Or do you require a mathematical proof against infinitude? I'd be happy to provide that, as well.
Perhaps you missed the bit about omnipotence.
And as numinus has already said, physical cosmology's explanation is literally no better in this regard.
