Up 5 lbs in one night? Is this normal after a large meal?

I've learned that *every single time* I have popcorn, I will be up 2 pounds the next day. It's like clockwork. It's not real weight gain. The most important thing about this realization is that I don't let the scary jump on the scale derail me anymore. I used to see it and feel completely defeated - that I would never, ever be able to have a treat ever again because having one would wipe away 2+ weeks of hard work. Not true. Weighing myself every day helped me make sense of these fluctuations. Using trendweight has helped me see the actual pattern of my weightloss.