Instead of looking at outdated softball rules, I found the actual rules:
http://www.ncaa.org/sites/default/files/2016-17DIMBA_PreChampManual_20170308.pdf
Section 2.1 Championship Format, Regional Format.
"If, for unforeseen circumstances, it becomes impossible to play a regional tournament game(s), the NCAA Division I Baseball Committee is authorized to determine which team in a respective regional shall advance to the super regionals. The inclement weather guidelines for regional competition are listed in the preliminary-rounds host operations manual."
http://www.ncaa.org/sites/default/files/2017DIMBA_PreRdHostOpsManual_20170524.pdf
Section 2 provides the same as above with regard to format (page 7).
Inclement Weather info on Pages 23-25. They are "guidelines" only
Here are relevant guidelines:
1. If Games 1 and 2 on Friday are both cancelled . . . play Games 1 and 2 on Saturday, play Games 3, 4 and 5 on Sunday and Games 6 and 7 (if necessary) on Monday. (0 – 2 – 3 – 2)
14. If both games are cancelled on Friday and both games are cancelled on Saturday . . . play Games 1 and 2 on Sunday, Games 3, 4 and 5 on Monday and Games 6 and 7 (if necessary) on Tuesday. (0 – 0 – 2 – 3 – 2)
This rule may also come into play:
"All regional competition should ideally be completed not later than the Monday before the start of super regional competition."
If they don't finish any today and can't get 2 in Sunday, we may see them call the whole thing off Sunday night because what good does 2 games do for you on Monday?
The bottom line is discretion is left to the NCAA Division 1 Baseball Committee. Hopefully the rain stops and we get 2 in today.