2012-13: McAdam returned to Waterloo for his second full season, splitting the goaltending duties with fellow 2013 NHL Draft prospect Cal Petersen. In 31 games he was 17-9-3 with two shutouts and had a 3.45 goals against and .896 save percentage. He appeared in two games in the playoff series with Fargo, making one start, and was 0-1 with a 3.22 goals against and .922 save percentage. The Black Hawks represented the USHL in the pre-season 2013 World Junior Club Cup in Omsk, reaching the semifinals, and in four games McAdam was 3-1 with a 2.17 goals against and .915 save percentage. He represented the USA in the 2012 World Junior A Challenge and was 4-0 with a 2.18 goals against and .927 save percentage for the gold medal-winning squad. McAdam was ranked sixth amongst North American goaltenders in Central Scouting's final rankings prior to the 2013 NHL Draft.