Cindy,
Great question and something I had not mentioned yet as I knew it would come up.
Eagle is right in the salt/bbq sauce but there is more to it than that.
Whenever we go into calorie deficit, we use stored energy in the body to fuel our metabolism (burned mostly in organs) and our activities of daily living & exercise.
One of those stored energy sources is glycogen, a form of stored carbohydrate. It is stored in our muscles and liver. Each gram o f the stored glycogen is complexes with 3 to 4 grams of water (Stubbs RJ.
Carboyhydrates and Energy Balance, Annals of the New York Academy of Sciences 1997; 819:44-69 among others).
Because of this relationship between water and glycogen, when you start to use glycogen for energy, you lose that water as the glycogen is broken down into glucose for blood sugar. Much of the initial weight loss in any diet is water. That is not a bad thing, but is reality. Within a few weeks, you typically replenish glycogen stores and the water comes back, and that isn't a bad thing either. Keep in mind, fat is being lost at the same rate as long as you are in calorie deficit.
That's why I've coached graphing weekly weigh-ins so people can understand what is going on over the long term. Weight loss over time graphed weekly will usually look like a stair case, not a ski slope as people would like. Those steps on the stairs are "paying back the scale" water you lost due to glycogen stores. Totally normal.
Now for the funny part, this water trick is what many of the high-protein and anti-grain diet and anti-fruit (the low-carbers) gurus use to get people "hooked" on the book, foods, supplements or whatever is being pitched with the program (Kreitzman SN, et al. Glycogen storage:
Illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition. American Journal of Clinical Nutrition 1992; 56:292S-3s).
Anyway, you're doing great and don't worry about this water gain/loss. If you're behaviors are consitent, you're fat loss will still be consistent but a scale can't tell you that, only body fat assesment or even a good pair of tight jeans getting looser

That is why I coach the weekly weigh-ins and not daily weigh-ins so people can see the trend over time. Monday weigh-ins are good becuase they show people the damage they are doing on the weekends. Most people weigh the least on Friday, which only causes them to relax their good behaviours on the weekend.
If you graph out weight loss over time, it will look like a stair case, not a ski slope, as you will naturally gain and lose water. The steps on the stair case are usually those water gains unless you just blew your calories so far out.
The great thing is you are "planning" before attending foody events-and there are so many foody events in our American culture- which is part of the sustainable behaviours I've been coaching. The "diet" mentality would have you either not go to foody events (how long could you keep that up?) or just forget about what happened and start over Monday. Neither is an approach that will work long term.
How are you feeling now that you're losing?