Iwan Moore’s 90th minute penalty settled a close-fought game in Nefyn’s favour.
With these teams having drawn 0-0 back in December, another tight contest was expected.
Playing against the strong wind in the first half, the Penwaig defended extremely well with keeper Dafydd Jones producing some excellent saves.
Nefyn took the lead against the run of play on 18 minutes when Steve Jones played a fine ball to Llyr Evans, who lashed into the top corner.
Five minutes before the break, Noel Owen equalised for the Anglesey side.
The second half was always going to be tough for Bay with the gale force winds in their faces and the youngsters did well in difficult conditions against a far more experienced side.
Trearddur’s Cameron Buckley received a second yellow in the 71st minute, leaving the visitors to tackle the latter stages with 10 men.
Bay kept Nefyn out until the hosts were awarded a 90th minute spot-kick which Moore dispatched well.
Hat-trick hero Jamie Haggas bagged a winning goal for Llanfairfechan two minutes into added time at the end of the 90.
It was Haggas who struck first for the visitors on 10 minutes, but Cameron Vaughan soon brought Bow level.
Jenson Wold put the Prestatyn hosts 2-1 up on 34 minutes, only for Haggas to make it all-square before the break.
The second half went to-and-fro until Haggas settled it late on with his third goal of the day.
Championship leaders Y Glannau were on course to make it three wins out of three until Rhodri Roberts put away an 88th minute equaliser for the Anglesey visitors.
The hosts had led since Carl Murray broke the deadlock in the 35th minute.
A very good battle in windy conditions at Dinorben Field saw both teams put in a great effort.
The game was played in good spirit and the sides tried to produce quality football.
Murray edged the St Asaph team ahead with a fine run and finish into the bottom corner from the edge of the box.
Hayden Nicholls pulled off two fine stops to prevent Gaerwen going into the break level.
Both sides had chances in the second half before two minutes from time Gaerwen equalised.
After a good move down the left, the visitors had two shots blocked before Roberts put away the third attempt nicely.
Both teams then had a chance to win it, but neither was taken.
Danny Warren scored twice for Airbus in their 3-1 win over champions Llandudno. Picture: FAW…
Can Bangor City 1876 reach their second cup final of the season on Saturday afternoon?…
The unstoppable Kirstie Kural. Picture: SAM EADEN FAW Kirstie Kural of Wrexham Foresters has now…
Asa Thomas is flying up the Bob Brodie Trophy chart and could yet produce the…
The goals keep coming for the relentless Meilir Williams Meilir Williams' hat-trick in CPD Llanuwchllyn's…
Can Bangor repeat their double success of last season? Saturday, April 18, sees the start…