No. This is not published online. It is announced to guests that are in the parks that they must exit the water and slides are closed but I am not aware that it is published anywhere else.
The water parks aren't technically closed due to lightning, but all attractions are. If there is lightning within a 15 mile radius, they will clear all attractions. Once there has been no lightning for 30 minutes, they will reopen. Of course, at a water park all attractions are impacted and there is not much else to do (note that rain alone does not close the slides and pools, only lightning). You might find an app that will track the lightning, though it may not match Disney's information exactly.
Sorry, but there is no early enough messaging for closures. You’ll have to go there to find out. What you really need to look at in this case is the hour by hour weather.