"We're last place in the league with our [penalty kill], so we've been slowly trying to bring it around," Armstrong said. "That should help our percentages a bit."
Armstrong stole the puck twice for two clean chances, the second a three-quarter ice race to the net.
"He's a gamer," Utah coach Kevin Colley said. "To score a couple shorties obviously gives you momentum. It was a huge period for us, and I liked the way we kept on pushing through in the third.
"It's been a long time since we played a third period like that."
To cap the second period, Utah forward Colin Vock, sent sprawling behind the net, sprang to his feet and skated unnoticed behind Thunder (17-10-4-3) goalie Tyler Bunz. Utah's Brad Mills' surgical pass gave Vock a wide-open net with 3 minutes, 18 seconds to play in the period.
Later on, in the third period, Vock scored a franchise record third short-handed goal.
Utah goalie Andrew Engelage complemented the Grizzlies' offensive outburst with a series of saves. Engelage was a brick in goal and needed to be.
"Having Andrew in net is a big lift for our club," Colley said. "When we got run around a little in the first period, they could have had a goal or two."
The first period was notable for its missed chances, of which there were several.
Certainly, Trevor Lewis, who scored for his third consecutive game with Utah on a third-period assist, would like to have back his off-target effort during a power play at the 9:50 mark.
Lewis, who had enough time to line up a putt, fired high and wide.
Donovan and Vock also went begging as the puck found them in the Stockton crease.
O Utah sets a franchise record with three short-handed goals.
• Riley Armstrong scores his 13th and 14th goals on a pair of short-handed chances.
• Grizzlies forward Colin Vock scores two goals and center Mitch Wahl adds one.