Former U.S. Open champion Corey Pavin carded a 4-under-par 68 to finish two shots back along with Hidemichi Tanaka, Steve Allan and Donnie Hammond.
Thunderstorms rolled through the area in the afternoon forcing multiple delays. Play was ultimately halted due to darkness and will resume Friday morning at 10:00 a.m. (ET).
Thatcher played the back side first at Montreux Golf and Country Club and hit an 8-iron inside 3 feet for a birdie at the par-4 10th. Thatcher followed with a birdie at the 11th and played his tee shot to 4 feet for a birdie at the par-3 12th. He added a birdie at the par-four 13th to make it four in a row out of the gate.
'I got off to a great start,' said Thatcher. 'The kind of start you dream about.'
The 27-year-old knocked his approach within 12 feet of the cup for a birdie at the par-4 15th and kept the run going with a birdie at the par-5 17th.
Thatcher tallied a birdie at the par-4 third and ran off a string of pars from that point on before the first delay hit. Upon returning to the course, Thatcher bogeyed the par-4 eighth for his only dropped shot of the day.
'I had visions of picking up one or two more but finished by dropping one,' said Thatcher.
Wiebe, who underwent elbow surgery in 2001, avoided the weather problems thanks to an early draw and picked up a birdie at the par-3 12th, his third. Wiebe then birdied two in a row starting at the 17th to make the turn at 3 under.
The 46-year-old collected a birdie at the first and hit an 8-iron inside 5 feet for a birdie at the par-4 eighth to complete his bogey-free round.
'This year has been fun,' said Wiebe, whose last PGA Tour win came at the 1986 Hardee's Golf Classic. 'Playing Nationwide, seeing some progress.'
Marc Calcavecchia was at five-under through 11 holes when play was called for the day. Kevin Sutherland, also through 11, was in a group of players left on the course at minus-four.
John Rollins, Carl Pettersson, Joel Kribel and J.J. Henry are in the clubhouse at 3-under-par 69.