Holders Derry progressed to the Dr McKenna Cup final as they edged out Down 0-11 to 0-9 in Sunday's opening semi-final at the Athletic Grounds.
Aidan Carr's three points helped Down lead 0-4 to 0-3 at half-time but Derry hit four unanswered points after the break to take control.
Conleth Gilligan finished with five points while Down's Kalum King was sent off in the closing stages.
Derry will face Tyrone in the decider at Armagh next Saturday (1945 GMT).
Paddy Bradley started for Derry and he notched the opening point of the game which was quickly followed by a Gilligan score.
However, Down fought back with four unanswered scores with Dan Gordon adding to three Carr points.
Probably the most memorable incident of the first-half was the sight of respective managers John Brennan and James McCartan exchanging words just before the break with the Down boss' attempts at using humour to diffuse the situation, not appearing to work.
A low-scoring first half concluded with Bradley notching another Derry point to leave the minimum between the sides at the break.
The key period of the contest came immediately after the break as Lynch's thumping score from long-range started a run of four unanswered Derry points, with Gilligan (two) and Caolan O'Boyle also on target.
Two Carr points again left only a point it but Derry reasserted control with successive scores from Gilligan, Gerard O'Kane and Bradley.
Points from Mark Poland and Arthur McConville left only two points between the teams with three minutes remaining but King's sending-off for an apparent stray boot aimed at a Derry player was followed by another Gilligan score and McConville's closing Mourne score proved academic.
Power NI Dr McKenna Cup semi-finals - Sunday, 22 January
Derry 0-11 0-9 Down
Tyrone 2-12 1-4 Fermanagh