During the 2019 season, Lowther played for the Bowie Baysox of the Double–AEastern League,[16] going 13–7 with a 2.55 ERA over 26 starts, striking out 154 batters over 148 innings.[17] Lowther did not play in a game in 2020 due to the cancellation of the Minor League Baseball season because of the COVID-19 pandemic.[18] On November 20, 2020, Lowther was added to the 40-man roster.[19]
Lowther began the 2021 season at the Orioles' alternate site in Bowie. On April 25, 2021, Lowther was promoted to the major leagues for the first time.[20] He made his MLB debut that day against the Oakland Athletics, pitching a scoreless ninth inning.[21] The next day, the Orioles optioned Lowther back to their alternate site.[22] The Orioles assigned him to the Norfolk Tides of the Triple–AInternational League, and then promoted him to the major leagues for his first start on May 8;[23] he allowed seven runs in two innings pitched.[24] Lowther returned to Norfolk after the game, and was promoted back to the major leagues in June.[25]
Lowther competed for a spot in the Orioles starting rotation in 2022,[26] but began the season with Norfolk. Lowther made 1 appearance with the Orioles, pitching 5.1 innings with 5 earned runs, and was designated for assignment on June 15 following the claiming of Jonathan Araúz.[27] He cleared waivers and was sent outright to Triple-A Norfolk on June 22.[28] He made 17 total appearances for Norfolk in 2022, struggling to a 10.31 ERA with 46 strikeouts in 43+2⁄3 innings pitched.
Lowther missed the start of the 2023 season due to injury, and began a rehab assignment with the rookie–level Florida Complex League Orioles in June. After one appearance, Lowther was released by the Orioles organization on June 9, 2023.[29]
On July 3, 2024, Lowther's contract was purchased by the Toros de Tijuana of the Mexican League.[31] In 5 games (4 starts) for Tijuana, he posted a 2–1 record and 2.19 ERA with 40 strikeouts across 24+2⁄3 innings pitched.
Lowther's father, Marc, coached him from the time he was six years old through his career at Cuyahoga Heights.[2] He and his wife, Brianna, have one daughter, born in January 2021.[33]