[1] McDowell was born in 1956 and was educated at Annadale Grammar School, an all-boys grammar school in south Belfast, Northern Ireland.

He studied history at Queen's University Belfast, graduating with a Bachelor of Arts (BA) degree.

He also holds a diploma in business studies from the London School of Economics and a Bachelor of Theology (BTh) degree in theology and biblical studies from Trinity College Dublin.

[2] He initially served as Curate of Antrim, in the Diocese of Connor (1996–1999), and subsequently Rector of Ballyrashane, in the same diocese (1999–2002), and Rector of St Mark's Church, Dundela, in the Diocese of Down and Dromore (2002–2011), during which time he was also an Honorary Secretary of the General Synod (2008–2011).

[6] On 14 September 2021, he was enthroned during a service at St Patrick's Cathedral, Armagh.