UPDATE: we ended up going to the party. We made some fruit punch and had a great time. In fact, right after I posted to here, he came up to me without me saying anything. He told me he wouldn't feel comfortable driving out of there were whiteout conditions, so he'd keep an eye on the forecast.

It didn't snow the entire time we were at the party until late when we were about to leave. It ended up being better than expected. And he was understanding and put our safety first without having to say anything. I felt relieved and thankful.