I have my WW meetings on Tuesday nights at 5.30. I'll eat breakfast, am tea break, lunch and 3 pm teabreak as normal as well as drinking water when ever I'm thirsty. The only thing I don't do is eat dinner before I go.....
But I do think you need to weight until your official WI before panicking about STS or whatever, remember your body can fluctuate up to 5 lbs in a day...... you may get a good result tomorrow but it's just not showing up yet.
good luck for the "official" wi