um, guys....all you ney-sayers.....please re-read the original posting a bit closer. Points of note:
*Stock summers (which are horrid in snow, about 3% traction)
*Parked outside AFTER snow started falling 'Maybe an inch or two had fallen' (not dry pavment, on snow)
When I bought my WRX (Feb '11) we had 1 snow right after I bought it. I parked at my apartment in a sloped driveway, in gear, with the break on after a few inches fell one night....when I got out and closed the door it started sliding back down the hill very slowly. I jumped back in and parked elsewhere on flat ground.
completely possible, and I have seen similar happen.