Two goals in the final quarter of the game ended Ashton Athletic’s hopes of booking a place in the final of the Partners Foundation Lancashire FA Challenge Trophy.
A goal down at half time, Athletic drew level just after the hour through a wonder goal by Marcus Cusani, but within six minutes Patrick Lacey had regained the lead for Southport with his second goal of the game.
A third goal in stoppage time from Jordan Archer ensured victory for the Vanarama National League North side.
To reach this stage of the competition, Southport had seen off Holker Old Boys 5-2 in the opening round, and most recently won 3-1 at Garstang in the quarter final back in December, but they were given a tough test by a well drilled Athletic side who sit 57 places below them in the non-league pyramid.
Athletic fielded an unchanged starting line up from the one that faced City of Liverpool on Saturday, while Southport lined up with only four of the side that started against FC United of Manchester in their weekend fixture.
The opening period of the game began in brisk fashion, with the ball pinging from end to end as both sides enjoyed their share of territory and possession.
The first clear cut chance arrived on 14 minutes, and Athletic were lucky to escape when a cross from Southport full back Reagan Ogle found Jordan Archer in space, but from six yards out the striker sidefooted the ball wide of the post.
Ashton’s first goal threat arrived just after the midway point in the half, when lovely neat footwork from Marcus Cusani took him past a defender and into the box, but his attempt to squeeze a shot in at the near post was denied by Southport keeper Joshua Tibbetts.
It was another fine piece of individual skill that broke the deadlock on the half hour mark, when Southport took the lead with a neat piece of improvisation from Patrick Lacey.
A corner driven low into the box by Morgan Homson-Smith found Lacey, and despite the close attention of Ashton defenders, the Southport man’s neat back flick crept into the corner of net just inside the far post.
It was rough luck on Ashton who had up to that point, but they almost fell further behind four minutes before half time, with goalkeeper Martin Pearson having to make a fine full length diving save from a rasping Dion Charles shot.
But Athletic finished the half strongly, and created their best chance of the half in stoppage time, when Charlie Munro’s snap shot from Matthew Reid’s free kick narrowly missing the target.
They picked up where they left off after the break, with Luca Defreitas-Hansen heading wide from corner and Charlie Munro testing Southport keeper Joshua Tibbetts from distance in the opening minutes of the second half.
But the standout moment of the evening arrived just after the hour, when Marcus Cusani equalised for Athletic with a goal of the season contender.
Picking up the ball just inside the Southport half, Cusani strode forward and unleashed a zinger of a shot from 30 yards the clipped the underside of the crossbar on its way into the net.
It was an outstanding effort to pull the Yellows back level, but within six minutes Southport were ahead once more, with Patrick Lacey smashing home his second of the night from close range.
Southport continued to exert pressure, and after a Jordan Archer header rebounded off the crossbar, Jordan Richards was denied by a great reflex save from Pearson in the Athletic goal, the big keeper reacting quickly to tip a well struck shot to safety.
But as the game moved into stoppage time, Jordan Archer sealed victory for Southport when he had time and space to pick his spot with a header into the bottom corner of the net from a left wing cross.
Southport will now face Colne in the final, looking to lift the trophy for the first time since 2010.