Well I can only speak for Alabama, our governor issue a state of emergency which allow schools to request not to make up days, our system had 3 days built in, we missed a total of 3 days, the first day was a waste, it did nothing up here in North Alabama, the other 2 days were ices/snow. We are only making up the first day and they aren't even using the snow days! We had 2 half days, so we are going full days those days to make up for the 1 day missed. So our school year did not get extended out. Also years ago when swine flu was going around, schools shut down for several days, they did tack on days at the end of the year but said parents could send a letter in if they had vacations already planned and would be excused from making it up, which we did.
All that to say, I wouldn't count on snow day necessarily to make crowd predictions go down.