Rooney cut it to 3-1 at 10:41 by tipping in Brayden Pachal's backhand from the slot. The goal was upheld after Washington’s challenge for goaltender interference was unsuccessful.
Lapierre pushed it to 4-1 at 14:22 when he scored off a long, looping backhand pass from Sonny Milano.
"Sonny does some crazy things out there with the puck," Strome said. "We're going to call that the alley-oop, I think, from that one. He threw it up there and ‘Lappy’ made a great play to hit it off of one bounce and put it upstairs. There's nothing much the goalie can do there on that one."
Weegar made it 4-2 at 7:13 of the third period, skating into the high slot and beating Lindgren with a slap shot glove side.
Wilson scored into an empty net at 17:31 for the 5-2 final.
"We knew that they were sort of in the same position we are," Weegar said. "I wouldn't necessarily say they were a more desperate team because I thought we did play a good game 5-on-5. They obviously got some good bounces on the power play. I thought our power play, we needed to get one or two there, for sure. I thought our compete and effort was there 5-on-5."
NOTES: The Capitals, who are 10-4-1 in their past 15 games, hadn't held a playoff spot since Jan. 2. ... Ovechkin has 170 multigoal games, second in NHL history behind Gretzky (189). He also has had a multigoal game against 94 goalies, the most in NHL history. ... Ovechkin has 128 game-winning goals, trailing only Jagr (135) for the most in NHL history. ... Weegar, who had a game-high six shots on goal, is third in the NHL in goals by a defenseman (16). He trails Cale Makar and Roman Josi, who are tied for first with 17.