I've had a really bad feeling about tonight for a while aswell, lets hope we're both wrong & it's not the waterfall. IMO Fed doesn't / hasn't had enough time to put something together to bail it out even QE3 i can't see before end of month at the earliest. Moody's i think have ties with the FED so probably support the AAA. But if the others come out & support S&P's line then there's trouble. If the crap hits the fan tonight the only intervention in markets will be the circut-breakers kicking in.
Best outcome would be a sharp move down to complete the H&S & then recover by market close the pattern complete with out recovery would not be pretty.