Tyler Bozak scored for the Blues, and Jordan Binnington made 21 saves.
Graves broke a scoreless tie at 1:57 of the second period. Graves, who had just gotten out of the penalty box, beat Binnington in a race for a loose puck in left circle and chipped it in the empty net.
Newhook made it 2-0, burying a rebound off a slap shot by Graves with 7:23 left in the second.
Colorado added to its lead with 3:52 left in the second on a diving swipe of the puck by Jost, finishing off a rush moments after Grubauer got in front of a point-blank chance for Jordan Kyrou.
Colorado Avalanche score 3 in 2nd, beat St Louis Blues to take a 3-0 series lead
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Avs score 3 in 2nd, beat Blues 5-1 to take a 3-0 series lead
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Avs score 3 in 2nd, beat Blues 5-1 to take a 3-0 series lead
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Avalanche on verge of sweeping Blues in first round
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