Withdrawing ED app before results come out?

Is it possible to withdraw your ED application before results come out?
I’m in a little bit of a situation because I want to apply to my dream school early decision, but I am currently being considered for a Posse scholarship to Pomona College that will pay everything. I cannot afford my dream school without FA but I cannot depend on Posse either because I am in the last round and do not know if I’m one of the winners yet. I absolutely want to go to my dream school if Posse doesn’t work out which is why I wanted to apply ED. Posse results come out before ED application results. Is it possible to apply ED to my dream school and if, and only if, I get Posse withdraw it before the results come out?

Talk to your HS guidance counselor ASAP.