Philip Broberg and Alexey Toropchenko each had a goal and an assist for the Blues, who are the second wild card from the West. Jordan Binnington made 21 saves.
St. Louis has won 15 straight at home dating to Feb. 23.
“We utilized our speed and our physicality,” Blues coach Jim Montgomery said. “I thought we were able to be physical down low, we were able to skate with some speed through the neutral zone, and we were really committed to getting to the netfront again. Those first couple of goals, they’re really good screen goals. That [Radek] Faksa line was dominant tonight.”
Cole Perfetti and Nino Niederreiter scored for the Jets, who won the Presidents' Trophy as the team with the most points in the regular season. Comrie made four saves in relief.
Game 7 will be at Canada Life Centre in Winnipeg on Sunday (7 p.m. ET; CBC, TVAS, SN, TBS, MAX, FDSNMW).
“Carbon copy of what happened here in Game 4 (a 5-1 loss),” Winnipeg coach Scott Arniel said. “Played really well, played real strong for 30, 33 minutes. Terrible line change, gave up a chance. Next time out, throw the puck to their goaltender right into his glove. Make another line change. We're racing back on those, trying to get coverage. And then the third one, that was just (bad) coverage. We had a couple guys, three guys caught behind the goal line.
"We shot ourselves in the foot. Just some uncharacteristic things in moments. And the momentum swings. We were playing a really strong game and it swung. Just like Game 4. You hope you learn from it the first time, but obviously (it) happened again. Move on. Like I said to you guys before, after Game 4, the damage is done. We've got to go home. Take care of our business at home."
After Perfetti tied it 1-1 with a power-play goal at 5:43 of the second period, Nathan Walker put the Blues back in front 2-1 at 11:34, scoring on a tap-in from the top of the crease off a pass from Broberg from behind the net.
It was Walker's third goal in two games.
“Whenever you can contribute and get the win, that’s obviously better than not,” Walker said. “’Broby’ made a great play there and I was just in the right spot at the right time.”