Jerome came on as a substitute with 20 minutes remaining, and just several minutes after he replaced Garry O'Connor, his effort took a wicked deflection and left Hornets' shot-stopper Scott Loach with no chance and he saw the ball hit the back on the net.
Brum extend the lead to four points between 2nd and 3rd, but United have a game in hand when they are of course in action against Burnley on Monday evening.
In the meantime, Wolverhampton Wanderers sealed promotion to the top flight when Sylvan Ebanks-Blake netted the decisive goal a minute or so after the interval.
Cardiff's automatic promotion hopes took a massive blow when they were hit for six at Deepdale. Goals from Mellor (2), Parkin, Kennedy (OG), Brown and Williamson kept PNE's aspirations of a play-off place alive.