The course rating is calculated separately for each round and the numbers are usually close from round to round under the same conditions. However, there's some statistical fluctuation so what we do is use all of the scores from all rounds on the same layout to calculate the SSA so the official round ratings will be the same for the same score in all rounds on that layout in the event.
You can look at the course history online to see the SSAs and determine a typical SSA for a layout. So yes, you can provide a guide for what rating a score is likely to get under normal weather conditions. Here's the link:
www.pdga.com/course-ratings-by-course