Shawn,
Thanks for your input. Not sure how that would work. AS I mentioned in my original comment, I have my system set to go on every third day. So say that would be today (Monday), then the next cycle would be Thursday. I need to run twice a week for about 20 minutes per zone in absence of any rainfall within three days of at least 1″.
So I irrigate this morning (Monday) and then this afternoon it rains .5 inches today, 1.77 inches on Tuesday, 0″ rain on Wednesday (now plenty of water for at least the next 3 days or more) and on Thursday, my system is ready to water at 100% and goes on. This is exactly what happened last week. The system seems to only look at the day preceding the day to irrigate. I want it to look at several days (at least 3 but better 7).