Scannell’s neat finish just before half-time was enough to secure a 1-0 success and three points for the Terriers, who had lost their five previous visits to the City Ground, and leaves them sitting comfortably on 51 points.
It proved to be a frustrating afternoon for Dougie Freedman, who is expected to sign a long-term contract this weekend, following talks with Forest owner Fawaz Al Hasawi, with the Reds producing their most disappointing performance of his tenure so far.
Huddersfield keeper Alex Smithies had to make superb saves to deny Tyler Walker and Michael Mancienne, but Huddersfield might also have won by a bigger margin.
It had been an even first half, but one in which neither side had managed to properly spring into life when it came to mustering sustained attacking threat. Forest had more of the ball but it was the visitors who managed to have the better of the chances.
James Vaughan sent a header spinning narrowly over the bar after attacking the ball powerfully at the near post, while Jacob Butterfield twice drew awkward saves from Karl Darlow, with low, skimming shots from range. Oscar Gobern might have done better when Nahki Wells’ driving run and cross picked him out by the penalty spot, but he sent his shot right at the keeper.
Forest’s opportunities had been less clear cut, with on loan Arsenal man Chuba Akpom firing tamely wide after creating the room for a shot with a superb run.
Chris Burke had been Forest’s most lively influence, down the right flank, seeing one driven shot charged down and a later effort palmed superbly around the foot of the post by Smithies, diving low to his right.
After Vaughan had spurned a good chance, Forest failed to take the warning – and Huddersfield took the lead two minutes before half time. A fine ball from Butterfield was central to the goal, sending Scannell angling into the box, where he beat the advancing Darlow with a precise, prodded finish that found the bottom corner of the net.
Burke continued to be Forest’s biggest source of threat, firing just over from 20 yards as the second half began and then coming even closer in the 55th minute, as his left foot strike flew a foot wide of the upright, with Smithies beaten.
Substitute Tyler Walker almost drew Forest level when he pounced on an Antonio cross from the right at the near post, but Smithies made an outstanding, brave save at the striker’s feet. Burke, yet again, came close with another curling shot, although Vaughan also sent a volley close for Huddersfield.
And Smithies had to pull off another outstanding save to thwart Forest, this time pushing away a towering header from Michael Mancienne, after Burke had delivered a corner.
Former Forest man Ishmael Miller missed a fine opportunity to make it 2-0 in injury time, after coming off the bench.