A rookie on the PGA Tour, Werenski enters Saturday's third round leading a tournament for the first time after 36 holes. He had six birdies and two bogeys before draining a six-foot putt for eagle on the par-five 18th at the Montreux Golf and Country Club course.
The event is scored using the Modified Stableford System, which awards eight points for a double eagle, five points for an eagle and two for a birdie. Bogeys result in a loss of one point and double bogeys or worse mean a loss of three points. Pars don't affect the score.
Play was suspended for 77 minutes late in the round due to poor weather, but the players were able to return to the course.
Australia's Appleby had six birdies and two bogeys to move to 24 points and sole possession of second place. He is one point clear of four players.
Greg Owen of England tallied eight birdies and two bogeys and was tied with Americans Luke List, Ben Martin and Dicky Pride with 23 points.