I believe you want something like the following:

(.*?)(?:WHEREAS|SECTION)

And make sure you check the "Case sensitive" checkbox or else it does fun things like stop at "Section 403.19" in the WHEREAS example.

This pattern assumes that the WHEREAS and SECTION markers will always be uppercase and that those words will never appear capitalized within the paragraph above them.  Things get more complicated if that's not the case...

Here's a quick explanation of the pattern:

1. The first set of parentheses says "this is the part I care about"
2. The . means any character and the quantifier *? says "0 ore more, but lazily instead of greedily" (meaning it'll capture as little as possible where the pattern still matches instead of trying to grab as much as possible while still matching the pattern, which is the default for a * quantifier)
3. The (?: ) parentheses are a non-capturing group, meaning we need them for an expression (an alternation in this case) but don't actually care about them otherwise.
4. And inside those parentheses is a simple alternation, meaning look for THIS word or THAT word.