Please help me??

I am having a situation at home this morning but I have to be at work in an hour. I want to take the whole day but I decided to go in late. My attendance is pretty good. However, my boss is a mean, condescending ***** who verbally abuses the employees over any attendance issue- even in bereavement (I've been there done that with her). How can I call in this morning? I just need to be a few hours late and haven't done this in a year. I will have to talk to her unfortunately. But how do I handle it????