Lee's goals, sandwiched around a key shorthanded tally by defenseman Kevin Lind, built a 3-1 lead for the hometown Fighting Irish midway through the second period, and Costello iced the win by scoring twice in the game's final 86 seconds.
With the loss, UND (6-4-2, 3-1-2 WCHA) dropped to 1-4-1 on Saturdays after last night's 2-1 win gave the team a near-perfect 5-0-1 Friday mark.
Lee opened the scoring 7:23 into the game, but that early lead was short-lived. UND sophomore Mark MacMillan answered less than two minutes later, completing a picturesque passing play with linemates Danny Kristo (Sr., Eden Prairie, Minn.) and Corban Knight (High River, Alberta). Knight found Kristo in the neutral zone and Kristo and MacMillan broke into the Irish zone on a 2-on-1. Kristo threaded a cross-ice pass to MacMillan, who one-timed the puck past Notre Dame goalie Steven Summerhays for his team-leading sixth goal of the season.
UND appeared to have built considerable momentum, as a pair of Notre Dame penalties immediately after the goal gave UND a 5-on-3 power play for a full two minutes. But Knight was whistled for a penalty of his own just 19 seconds later, reducing the advantage to a 4-on-3. Forty-three seconds after that, Lind beat Gothberg with a long-range shot from inside the blue line to restore an Irish lead Notre Dame would not relinquish.
Lee extended the cushion to 3-1 with his third goal of the weekend at 13:30 of the second period.
UND put forth arguably its most effective period in the final 20 minutes, maintaining a heavy territorial edge in an effort to climb back into the game. But Summerhays was equal to the task at nearly every turn. Rocco Grimaldi's (Rossmoor, Calif.) goal with 1:13 remaining, after Costello had just made it 4-1, was Summerhays' only blemish of the period.
Costello finished the scoring with an empty net goal with 19 seconds left on the clock.
Summerhays finished with 30 saves on 32 shots, while Gothberg made a career-high 36 saves on 40 shots.
Both teams went 0-for-5 on the power play, with UND managing just two shots on goal with the man advantage.
North Dakota will return to WCHA play next weekend when it travels to Colorado College.
Notes: Knight's second-period assist extended his point streak to a career-best seven games, the longest on the team this season. He has nine assists during that stretch ... Linemate Kristo extended his point streak to five games, although his 3-game goal-scoring streak came to an end ... Lee, Lind and Summerhays were named the game's three stars.