According to the USPS s website, it should take two days to arrive. So, you should be receiving it today or tomorrow (Wednesday) depending when the post office in Michigan actually received it (sometimes the company says it was shipped in the morning, but the post office doesn t actually received the package until the evening).
I think Wed. is more realistic for your delivery. The post office isn t quite as efficient as UPS in moving packages overnight, unless you paid a premium. The Post Office s priority mail is not the same as their Express Mail that would have included overnight delivery.