YES, very normal; it's all a part of the process. That's why it is often recommended to weigh only ONCE A WEEK. The other posters have all mentioned the main reasons for this (TOM, salt/sodium, rigorous exercise, constipation), plus if you are on your legs & feet a lot, that can also cause them to swell and hold water. I have a big issue with that, so I have to put mine up 1-2 times a day.
It should regulate itself out in a few days ...