McKennis had never finished in the top three before coming down the Karl Schranz course in 1 minute, 14.62 seconds to beat Daniela Merighetti of Italy by 0.07. Anna Fenninger of Austria was third, and overall World Cup leader Tina Maze of Slovenia finished fourth.
Vonn, the defending overall champion who returned to the circuit after recovering from an intestinal illness, was 0.34 behind. American teammate Laurenne Ross was fifth.
Because snow at the top of the course was too soft, organizers decided to use the lower super-G start, shortening the initial 2.2-kilometer long downhill course.