A blinding flash of the obvious

Without more context, I assume this is a sarcastic/ironic way to say that someone finally noticed something that had been obvious. "Blinding flash" is usually used to refer to a startling discovery. I believe the reference is to Paul's experience on the road to Damascus. You wouldn't need a "blinding flash" to see/ understand something that was already obvious.

Thanks a lot Delmobile

I think there's a bit more subtlety to it than that (if anyone's still interested 5 years later!) Once you see it it's blindingly obvious. Until then it's profoundly obscure. What's interesting about this is that something which is blindingly obvious to you is completely obscure to me. Your efforts to explain it to me will probabaly be unsuccessful. When I see the blinding flash I will finall

I agree with you David. That's the way I've always understood it. It was a favourite phrase of my mother's as a self-deprecating utterance, and whenever I use it in the same way I do so in honour of her. But now I must admit that I'm not sure that I'm agreeing with you after all. C'est la vie.