After finishing 36 holes of stroke play at 2-over 146, Wightman survived a 14-man playoff late Tuesday to advance to match play. Eleven hours later, he was on the tee against Jimison, who won the stroke-play medal with an 11-under 133 at The Orchards Golf Club.
Jimison was 2-up after five holes, but Wightman won the next three holes to go ahead. The match was even after 13 holes, but Wightman won No. 14 with a birdie and 16 with a par.
Jimison, playing his first match-play event in five years, stayed alive by winning the 17th, but hit his approach shot into the water on 18 to end the match. Wightman is to play 33rd-seeded Luke Stephan in Thursday's second round.
The stroke-play medalist has only gone on to win the tournament once in the past nine years.
Michigan State senior Eric Jorgensen, who was seeded second, defeated Nick Becker, while third-seeded Alan Hill and No. 4 Lee Williamson also won.
Fifth-seeded Derek Tolan, who played in last month's U.S. Open at the age of 16, lost to No. 60 Jake Grodzinsky.
Other winners included defending champion Chez Reavie and U.S. Junior Amateur champion Henry Liaw, but 2001 runner-up Danny Green and first-round stroke-play leader Hunter Mahan both lost.
The winner of Saturday's 36-hole final will receive an invitation to the 2003 Masters, as long as he does not turn pro in the meantime.
The tournament is open to amateur golfers who do not have playing privileges on a private course.