The difference between the two sides is now four points and the game in hand may still prove vital for Northwich.
It was the home side who stormed into a two-goal lead and might have had more as the Rovers defence fell away at every opportunity.
A powerful shot by Paul Brayson, given space inside the box to collect a throw in, beat Dean Williams at full stretch in the 13th minute.
Then Des Lyttle was content to guide a Danny Mayman free-kick out at the far post when Johnny Allan stuck a boot between his feet and put the ball over the line.
Rovers were rallied by veteran Paul Warhurst's 24th minute header straight from the good old days. Mo Harkin took the free-kick and found Warhurst on the edge of the six-yard box.
It gave Rovers the initiative and Kristian Rogers made spectacular saves from a Charlie Griffin header, an Andy Harris long ranger and an overhead kick from Warhurst in quick succession.
After the break Forest Green's spirit only took them so far and Northwich's defence smothered a succession of attacks.
The nearest the visitors came to scoring was a volley from Griffin which dipped just wide of the post.
Williams kept Rovers' hopes alive on the night with a fine save from Francis Tierney but the goalkeeper was lucky in injury time when Brayson clipped the post.