Winnipeg took an early lead when Zach Benson scored 4:11 into the contest, beating Thomas Milic with a high wrister just inside the left post.
Seattle tied the game 1:24 into the second when defenceman Jeremy Hanzel one timed a Reid Schaefer feed past Ice goaltender Daniel Hauser.
Seattle took control of the contest off of two turnovers early in the third period scoring a pair of goals eight seconds apart.
Jeremy Hanzel also scored for Seattle.
Dylan Guenther had three assists.
Thomas Milic made 28 saves for the Thunderbirds, who saw their playoff record move to 13-3.
Seth Benson scored twice for Winnipeg.
Daniel Hauser turned aside 35 shots for the Ice, who dropped to 13-3 in the post-season.
Seth Benson scored 4:11 into the contest when he took a pass from Graham Sward before stepping into a wrister from the top of the left faceoff circle, beating a screened Thomas Milic high glove side.
The goal was his 5th of the playoffs.
Jeremy Hanzel tied the contest 1:24 into the second after converting a partner pass along the blue line from Reid Schaefer, one timing it past Ice goaltender Daniel Hauser from the right point beating him low blocker side.
The goal was his 3rd of the playoffs.
Brad Lambert gave Seattle the lead just over five minutes into the third when Karter Prosofsky failed the to clear the puck and threw it blindly into the center of the ice.
Lambert picked up the puck, moved into the high slot and wired a wrister just inside the left post to make it 2-1 at 5:02.
The goal was his 4th of the playoffs.
Reid Schaefer made it 3-1 just 8 seconds later when he converted a Dylan Guenther feed and buried it to give the Thunderbirds a two-goal cushion.
Seth Benson scored his second of the night at 8:27 when he converted a Karter Prosofsky cross crease feed from in close to pull Winnipeg within one.
The goal was his 6th of the playoffs.
Seattle appeared to take a two-goal lead at 14:25 but the puck was batted in with a glove and ruled no-goal by referee Mark Pearce.
Brad Lambert sealed the win at 17:14 when he broke in alone and beat Hauser high glove side to make it 4-2.
SHOTS-SEATTLE 39 WINNIPEG 30