Hey, Professor! I hope this message finds you well. I'm writing to let you know that I'll need to take a day off from class tomorrow.
    I've had a family emergency that I have to attend to. It's unexpected and pretty urgent, so I'm afraid I won't be able to make it to class. I'm sorry for any inconvenience this may cause, but I'm sure you'll understand.
    Don't worry, though. I'll make sure to catch up on any missed work or notes. I'll ask my classmates for any handouts or important discussions we had, so I don't fall behind.
    Thank you for being so understanding and accommodating. I appreciate your flexibility and support. I'll definitely make it up to you by being extra attentive and engaged in class when I return.
    Looking forward to seeing you soon! Have a great day!