When there was only one goal in it at half-time the fans could not have anticipated the feast that was to follow.
Notts had edged in front with a well-worked and well-taken solo goal by Myles Weston in the 32nd minute.
It was Weston's first ever League goal at Meadow Lane and could hardly have been a better taken effort as he drilled the ball low into the corner.
Vale certainly had their moments in the opening half. Dave Brammer volleyed over the top, Sam Stockley shot badly wide and Josh Lillis - on his home debut - made a smart save from Danny Glover after good work by Louis Dodds.
Vale started brightly on the resumption and were rewarded when Simon Richman fastened onto a throughball and cracked it wide of Lillis.
The sides were only level for five minutes before beautiful link-up play between Weston and Matt Hamshaw set up Forrester for his first, a thrilling drive into the top corner.
It could so easily have been Forrester's second of the game having struck the bar from 30 yards inside the first minute of the action.
Notts didn't have long to wait for a third goal when a good knock-down by Delroy Facey was eagerly seized upon by Forrester for his second.
Moments later Forrester hit a thrilling effort over the top and it seemed the miss could prove costly when Scott Brown set up Dodds who beat Lillis with a fine glancing header.
A fourth Notts goal eight minutes from time finally sealed the points. Facey was fouled and Forrester completed his hat-trick by driving the spot-kick straight past Joe Anyon in the visitors' goal.
It was Forrester's third penalty conversion of the season and the first time Notts had scored as many as four in front of their own fans.