Martin Laird, Scott Sterling, Bob Burns and Matt Weibring each shot rounds of e8-under 64, and John Morse was in the clubhouse with a 7-under 65 when the round was suspended.
It was scheduled to resume Friday morning at 8:15 a.m. local time.
Ridings will almost certainly still own the lead when the first round is completed. There were just seven players remaining on the course, and only one of them was within three shots of his lead.
Ryan Blaum was seven under through 16 holes.
Ridings made 10 birdies without a bogey on Thursday. He made six birdies in his first 10 holes, then four over his final five. In between was his longest stretch of pars: three in a row from the 11th.
This is the first of just two events remaining before the season-ending Nationwide Tour Championship, which begins on Nov. 1 in California.
For players like Ridings, who claimed his only Nationwide Tour win in 2002, the importance of posting a good finish in the last two weeks is amplified.
He currently ranks 86th on the money list -- 26 places from making the field for the Nationwide Tour Championship and 61 spots from being in the top 25 and earning a PGA OUR card for next season.
Two players behind him -- Laird and Sterling -- are safely inside both lists, at 17th and 18th respectively on the money list.