The Oilers took a 3-1 lead into the final period and were 5:28 away from ending their second five-game losing streak of the season. But defenseman Yannick Tremblay made it a one-goal contest at 14:32 with his sixth goal and Snyder beat goaltender Tommy Salo 2:33 later from the right side for his fifth goal.
Viktor Kozlov started the play just inside the Edmonton blue line. He passed to Dany Heatley at the edge of the left faceoff circle. Heatley faked a shot, drawing Salo out of position, and fed Snyder, who was moving through the slot and put the puck in the right corner of the net.
Mike Comrie and defensemen Steve Staios and Eric Brewer scored for Edmonton, which avoided its first six-game losing streak since 1995 and moved seven points ahead of Chicago for the final Western Conference playoff berth.
Heatley assisted on both third-period goals and defenseman Daniel Tjarnqvist also scored for the Thrashers, who are 0-1-1 on a seven-game road trip.