Seattle ? The setting was perfect for Alex Smith to fail: His team was trailing, it was cold and wet, and the crowd expected another Seahawks’ division title.

Instead, with crisp, confident passes and nimble running, Smith put together the best 15 minutes of his young career.

Smith accounted for three fourth-quarter touchdowns – two passing, one running – and the San Francisco 49ers prevented the Seattle Seahawks from clinching the NFC West with a surprising 24-14 victory Thursday night.

“The boy just became a grown man today, baby,” 49ers’ running back Frank Gore said of his quarterback. “There’s a lot more to come.”

Keeping the 49ers’ slim playoff hopes alive, Smith tossed an eight-yard touchdown pass to Vernon Davis early in the fourth quarter, then capped a 10-play, 73-yard drive with a 20-yard TD pass to Gore with 4:01 left that sent soaked – and shocked – Seahawks’ fans for the exits.

One play after a delay-of-game penalty on third-and-1, Smith stepped out of Kelly Herndon’s grasp, scrambled and found Gore behind defense near the goal line. San Francisco’s players erupted into celebration, as the 49ers (6-8) broke a three-game losing streak and swept both games from Seattle.

“I think we always knew (we could beat Seattle),” Smith said. “I think that changed a couple of weeks ago when we beat them at our place.

“I think this team grew up a little bit tonight.”

If his fourth-quarter passing wasn’t enough, Smith faked the entire Seattle defense and jogged 18 yards for a touchdown with 1:42 left to cap a night when he looked just a little like Steve Young and Joe Montana.

The turnaround was startling, after the 49ers’ offense went the first 44 minutes with just four first downs and rarely looked threatening. The 49ers rolled up 196 yards in the fourth quarter.

Meanwhile, the questions only continue about the Seahawks. Seattle (8-6) lost its second straight divisional game, ending any hopes of getting a first-round bye in the playoffs.

Afterward, coach Mike Holmgren said inconsistency is Seattle’s identity.

“We need to find a way to win this week or next week or somehow,” Seattle’s Bryce Fisher said. “Otherwise there’s going to be a lot of us getting our lockers cleaned out.”

Smith finished 14-of-25 for 162 yards, a far cry from the first half when he was 5-of-12 for 38 yards and the 49ers best offensive play was a 33-yard run on a fake punt.

It was Smith’s completion to Antonio Bryant late in the third quarter that finally got the 49ers’ offense on track.

Smith’s 11-yard completion to Bryant with 48 seconds left in the quarter was San Francisco’s first first-down of the half. On the next play, Arnaz Battle beat Herndon off the line of scrimmage and Smith hit him in stride for a 54-yard completion.

Two plays after hitting Battle for 13 yards on third-and-10 at the Seattle 22, Smith rolled right and Davis got separation from safety Jordan Babineaux in the end zone.

With Smith finding holes in Seattle’s secondary, Gore put the game away. Gore, who ran for a franchise record 212 yards in the first meeting between the two teams, had 104 of his 144 yards in the fourth quarter.

“When we go at them, it’s hard to stop us,” Gore said. “We kept going downhill at them and they couldn’t hold up.”

Matt Hasselbeck threw a 22-yard touchdown to Jerramy Stevens with 9 seconds left, for the final margin, but Hasselbeck was outplayed by Smith.

Hasselbeck finished 20-of-37 for 220 yards, but threw a pair of interceptions, the most damaging on the first possession of the second half.

On second-and-11 at the San Francisco 20, Hasselbeck tried to hit D.J. Hackett on a seem route in the end zone. Instead, 49ers’ safety Mark Roman stepped in front of Hackett and intercepted the pass, returning it to the 27.

Shaun Alexander rarely found holes to run through in the second half. Alexander had just 16 yards rushing in the second half, and failed when Seattle needed 1 yard to keep its best drive of the fourth quarter alive.