Why does this say there is no join predicate?
It's happening here because the predicate slard.AreaNum IN ('40') is pushed to both ends of the Nested Loop Join operation.

I have a blog post about this same thing, but what it boils down to is that your WHERE clause matches a JOIN clause ON slard.AreaNum = ac.AreaNum

In these cases, the optimizer can push SARGable predicates to the the index access (seek or scan), because it's assured that whichever values come out will match.

This is called an implied predicate, and you can read more about them here:

Craig Freedman

Some Bozo

You can ignore the warning in this case.

Hope this helps!