The Baggies, although sharing the same points total as United, go top as they have have scored more goals.
The reversal at the City Ground brought the Magpies' four match unbeaten run to an end, and at the end of the day the visitors can have few complaints about the defeat. They were wretched for the opening 45 minutes and despite an improvement after the break they got what they truly deserved nothing.
Steven Taylor missed out on the trip to the City Ground after failing to recover from a hamstring injury, while Fabio Coloccini is still nursing a sore groin. In the first choice centre back pairing's place saw Zurab Kizanishvili line up with Danny Simpson at the heart of the defence. Ryan Taylor dropped in at right back and Jose Enrique returned to the starting line up after missing the home game with Bristol City. Argentina international Jonas Gutierrez had to be content with a place on the bench, his place was taken by Peter Lovenkrands, while Andy Carroll and former Forest striker Marlon Harewood were paired up front Forest took a deserved lead when the lively Dexter Blackstock, making his150th club career start, seized on on Paul Anderson's defence splitting pass, rounded Steve Harper and slipped the ball into the net on the stroke of half time. It was nothing more than the home side deserved after dominating the opening 45 minutes of the one-sided contest - creating several opportunities in the process.
The surprise was that it took the final minute of the first half for the hosts to take the lead. Billy Davies' side almost drew first blood when a towering header from dangerman Blackstock brought the best out of goalkeeper Steve Harper, who managed to scramble the ball away after only three minutes. Radoslaw Majewski then attempted to chip Harper three minutes later before Blackstock crashed a header against the visitors' upright from a Majewski corner.
The best Newcastle could offer at the time was a Carroll header which threatened only a home supporter sitting in Row Z.
United did have a couple of half chances themselves. Taylor hit the post from an audacious free kick 35 yards out just before the half hour mark, before Carroll, once again, failed to hit the target with his head moments later from the resulting corner.
Other than a weak Harewood header the Magpies were never in it.
Soon after, Anderson went close; Nathan Tyson flashed a shot by Harper's post, while Blackstock headed over from ten yards.
Anderson went closer still five minutes before the break and it looked only a matter of time before they opened the scoring as Newcastle were being outclassed in every department.
It was of no surprise to the home supporters when the half's two best players, Anderson and Blackstock, combined to give the Tricky Trees the lead.
United couldn't get any worse in the second period and they did at least try to step up the tempo from a lacklustre first half.
Chris Hughton's side missed a glorious opportunity to level five minutes in, but Lovenkrands blazed over when in a central position from Kevin Nolan's pass. The visitors then had a scrambled effort headed off the line, while Harewood also went close all in the opening ten minutes.
Nolan could have levelled in the 65th minute but, like several other efforts, it was wasted.
Substitute Gutierrez thought he'd levelled in the 70th minute when latching onto Carroll's flick from Taylor's cross but the linesman ruled it out for offside.
Gutierrez and Enrique attempted to weave some magic down the left in a bid to find an equaliser but found they were running down blind alleys.
Substitute Nile Ranger became one of the several guilty party, when, with five minutes remaining, flashed a header high and wide over Lee Camp's goal.
On the balance of play Forest deserved their victory and if Newcastle have serious ambitions of bouncing back in to the Premier League they'll have to learn to start from the first whistle, rather than after just 45 minutes.
Forest (4-4-2): Camp, Gunter, Morgan, Wilson, Anderson ( McGuggan, 78), Cohen, McKenna (Garner 85), Tyson, Moussi, Blackstock, Majewski, (McGoldrick, 61) Subs not used: Chambers, Smith, Adebola, McClearry, Newcastle: (4-4-2): Harper, Taylor R, Khizanishvili, Simpson, Enrique: Guthrie, Nolan, Smith, Lovenkrands (Gutierrez, 62), Harewood (Ranger, 82), Carroll: