Byrnes had her first international success at the ISF Snowboard World Championships in 1993 in Ischgl . There she won the silver medal. She made her debut in the FIS Snowboard World Cup in January 1997 on Kreischberg and finished ninth. The following month she took her first World Cup victory at Mount Bachelor and took third place in Kanbayashi . At the Burton US Open , she came in second place in 1997, 1998 and 1999, respectively. In the 1998/99 season she won six World Cups. In addition, she achieved second and third place once and won the Halfpipe World Cup. She was seventh in the overall World Cup. In the following season, she won the World Cup five times and finished second once. She achieved 17th place in the overall World Cup and second place in the Halfpipe World Cup. After placing 39 at the World Cup in Mont Sainte-Anne at the beginning of the 2000/01 season, she won her 13th World Cup victory in Kronplatz . At the peak of the season, the 2001 Snowboard World Championships in Madonna di Campiglio , she finished 13th. At the following World Cup in Asahikawa she managed to place sixth and at the end of the season she achieved 21st place in the halfpipe world cup . At the beginning of the 2001/02 season she came in second at the US Snowboarding Grand Prix in Mammoth twice and in third place at Mount Bachelor. At the 2002 Winter Olympics in Salt Lake City , she was sixth. In March 2002 she got her last World Cup victories in her only season participation in the World Cup in Sapporo and Tandådalen and thus finished eighth in the Halfpipe World Cup. In the 2002/03 season she reached third place in the US Snowboarding Grand Prix in Park City and Mount Bachelor. In March 2003 she came in third place at the World Cup in Sapporo and finished the season in 17th place in the Halfpipe World Cup. The following season she finished second at the US Snowboarding Grand Prix in Mammoth and third in Mountain Creek . She also finished third in the season at the World Superpipe Championships in Park City and second at the Burton US Open. In January 2005 she finished 13th at the Winter X Games 2005 in Aspen and fourth at the 2005 Snowboard World Championships in Whistler . The following year she finished sixth in the 2006 Winter X Games . At the Snowboard World Championships 2007 in Arosa she came in 13th place. In her last seasons she reached 17th place in the Winter X Games 2008 and 13th place in the Winter X Games 2009 .
United States
World cup
Whistler
Asahikawa
Olang
Tignes
Tandådalen