Near the south ends of SGRT and Coyote Creek the majority of the rain was over by Saturday night. At that time my wife and I drove to the Centralia overpass of the Coyote Creek and were impressed at how full it was. I would guess it was about 2/3 full. We've only been riding regularly in the area for a while, and we have never seen it like that!
Sunday morning - about 12 hours later - it was a completely different story. The water had declined considerably and only filled the small channel at the very bottom. I would guess it was less than 1/10 full. What a difference in just a short period of time! We reminded ourselves that it can fill up just as fast. The gates were still closed.
Monday morning I found a Bike Coordinator number and lots of other information at
http://dpw.lacounty.gov/bike I called and left a message and got a reply within half an hour. The man told me that he was no longer the coordinator (the number on the website is outdated), but he was able to give me general guidelines about when the gates are opened after a storm.
He said that generally the gates are open the day after the storm passes, as long as there is no more rain forecast for the next 24 hours. I don't know if the gates would be open so quickly if the day after the storm falls on a weekend.
Later on Monday I was able to ride my regular route along Coyote Creek and SGRT. The only obvious sign of the storm that I saw was a pile of debris along the trail on the west side of Coyote Creek beneath Centralia. It looked like the water had been that high.
Ride safe!