contacting advisor before admission can be helpful?
You could certainly talk with them and discuss your ideas and options and if you find the connection is a good one you could ask for a letter of recommendation from them, but short of a letter I don't think a professor has a whole lot of flex/power when it comes to admissions. 

Certainly if they vouch for you that is a positive thing, but unlike a "job" I feel the role at the University is based more on your academic experience and aptitude than who you know.