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Call Human Resources, he had no right to fire you. You might get a small severance or your job back... could be a tricky situation in the future if you retain your job. Either he will be looking for a reason to fire you in the future or he will be scared of HR and let you get away with murder.
You do have rights though as an employee, you should exercise them.
Call him monday and apologize that you weren't able to come in when he needed you and explain how you need to know in advance when your shifts are because when your not working at the mountain you schedule time to help out with your father's business.
He either says he can't tell you when your shifts are until the day of, at which point you either deal with the job requirements or you quit.
But most likely he'll apologize and say that he will let you know in advance from now on.