Fornaroli's first-half heroics came after the Jets took the lead in the sixth minute through Mark Natta, while Newcastle winger Clayton Taylor scored a brace.
Nishan Velupillay also scored a wonderful solo goal in the 55th minute to help Victory to a 2-0 start to the season, in front of a packed north terrace active area at AAMI Park.
Capped Socceroo Fornaroli, 36, now has five goals for the season as outright golden boot leader, while winger Daniel Arzani was super-impressive on the right.
Newcastle opened the scoring after they were awarded a contentious corner, when officials ruled the ball had gone out off Adama Traore.
From the set piece, Natta pounced on a switched-off Victory defence to tap home.
Barely two minutes later, Rai Marchan slipped the ball to Arzani, who beat Jason Berthomier then sent the ball skidding past the pack to Fornaroli, who buried his first-time shot.
Victory doubled their lead when Traore burst forward and whipped the ball into the box, with Fornaroli stretching to toe-poke home.
A few minutes later, Arzani combined brilliantly with Zinedine Machach, then won a free kick in a dangerous wide position.
The chaos resulting from Arzani's free kick caused Jets defender Carl Jenkinson to fall over and handball, and Fornaroli coolly buried the penalty to complete his hat-trick.
In the third minute of injury time, Machach slipped the ball out wide to Adama Traore, who burst down the left then squared a cross into the box.
The ball was behind Fornaroli but the striker curled his right leg behind his left to flick it into the back of the net.
Newcastle hit back in the 49th minute when Taylor volleyed home Dane Ingham's cross to make it 4-2.
Six minutes later, Velupillay burst away on the break then calmly dinked the ball past Ryan Scott.
Taylor had a header chalked off for offside in the 70th minute but completed his brace five minutes later after Trent Buhagiar burst cleared and squared the ball to him.
But Newcastle were unable to mount a dramatic comeback, while Fornaroli just fell short of a five-goal haul despite multiple close efforts.
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