first of all, no those weren't vibrations. when you feel vibrations, they feel like...well...your body is vibrating up and down, but you're not actually moving. they've become so intense for me that i've actually exited the trance state shivering. it's like you're sitting on a giant vibrational chair 
the white flash of light could really be a number of things. usually when i'm meditating, i tend to come across three different variations, and hopefully what you experienced is one of the three
1.) pulsing white rings from my third eye - these are usually at about 5 second intervals, and they float off into the distance without effect. i used to think they weren't anything except trying to hard, but i think they're a prelude to further achievements
2.) swirling and bright white light, perhaps with patterns or colors - this is what i get directly before i project. the light comes from the third eye, or simply swirls around in my visual field. sometimes patterns appear instead, and yesterday the light actually took on figure forms. after about 30 seconds, astral sight tends to set in
3.) sometimes i'll be laying there in the dark and all of a sudden the room will seem to get much brighter, and then fade back down again. this sounds like what you experienced, and i don't really have any theories on it. it's never helped me project, but it's always a nice feeling
of course, yesterday i saw a big blob of white light just out of nowhere, and it was the size of gigantic dinner plate, but this didn't end up doing anything for me
hope i answered your questions!

the white flash of light could really be a number of things. usually when i'm meditating, i tend to come across three different variations, and hopefully what you experienced is one of the three
1.) pulsing white rings from my third eye - these are usually at about 5 second intervals, and they float off into the distance without effect. i used to think they weren't anything except trying to hard, but i think they're a prelude to further achievements
2.) swirling and bright white light, perhaps with patterns or colors - this is what i get directly before i project. the light comes from the third eye, or simply swirls around in my visual field. sometimes patterns appear instead, and yesterday the light actually took on figure forms. after about 30 seconds, astral sight tends to set in
3.) sometimes i'll be laying there in the dark and all of a sudden the room will seem to get much brighter, and then fade back down again. this sounds like what you experienced, and i don't really have any theories on it. it's never helped me project, but it's always a nice feeling
of course, yesterday i saw a big blob of white light just out of nowhere, and it was the size of gigantic dinner plate, but this didn't end up doing anything for me
hope i answered your questions!