It's a return to Montreal for Weise, a forward who played 152 games for the Canadiens from 2014-16. He had an NHL career-high 29 points (10 goals, 19 assists) with Montreal in 2014-15 and scored 14 goals in 56 games for the Canadiens before being traded to the Chicago Blackhawks on Feb. 26, 2016.
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"Just something we've been working on for a few weeks with Montreal," Flyers general manager Chuck Fletcher said. "Want to thank Dale and Christian for everything they've done with the Flyers. Both players were looking for a bigger role and different opportunities so we tried to accommodate them going forward."
Weise signed a four-year contract with the Flyers on July 1, 2016. The 30-year-old had 11 points (five goals and six assists) in 42 games for Philadelphia this season before being waived on Jan. 15 and sent to Lehigh Valley of the American Hockey League, where he had a goal and an assist in three games.
Weise has 120 points (54 goals, 66 assists) in 481 NHL games for the New York Rangers, Vancouver Canucks, Canadiens, Blackhawks and Flyers. He also has 11 points (six goals, five assists) in 40 Stanley Cup Playoff games.
"We know that he had some good seasons here, he was very good for the Canadiens, and he's a good teammate," Canadiens coach Claude Julien said. "He brings experience and we've lost (Michael) McCarron for the rest of the year so we have to make sure we have enough depth here, but also in Laval."
Folin is in his sixth NHL season. He had two assists in 26 games this season for Philadelphia, averaging 15:33 of ice time. The defenseman, who turned 28 on Saturday, has 38 points (seven goals, 31 assists) in 209 NHL games with the Minnesota Wild, Los Angeles Kings and Flyers.
"I think we have a lot of players, whether it's (Mike) Reilly, (Victor) Mete, (Brett) Kulak, etc., guys who are very mobile who move the puck well," Julien said. "Here we went and got a guy with good size (6-foot-3, 204 pounds) who can over time give us some depth on that size. So it changes the look of our group of defensemen."
Schlemko had two assists in 18 games for the Canadiens this season, as well as four points (one goal, three assists) for Laval of the AHL. The 31-year-old defenseman is in his 11th NHL season and has 94 points (18 goals, 76 assists) in 415 games for the Phoenix/Arizona Coyotes, Dallas Stars, Calgary Flames, New Jersey Devils, San Jose Sharks and Canadiens. Montreal acquired him in a trade with the Vegas Golden Knights on June 22, 2017, one day after he was selected by Vegas in the 2017 NHL Expansion Draft.
Froese signed with the Canadiens as a free agent on July 1, 2017, and played 48 games for Montreal last season, finishing with 11 points (three goals, eight assists). The 27-year-old forward has spent all of this season with Laval, where he was captain and had 30 points (14 goals, 16 assists) in 46 games. He has 16 points (five goals, 11 assists) in 110 NHL games for the Toronto Maple Leafs, Tampa Bay Lightning and Canadiens.
"Adding David Schlemko, a player with a lot of experience in the League, a defenseman who can play left side, can play right side, along with Phil Myers, we think Myers and Schlemko can give us pretty good depth in the NHL," Fletcher said. "Byron Froese is a young man, has played 100 games in the NHL, he's captain of his team in Laval. He's a real top two-way player at that level and a player who has shown he can add depth."
NHL.com Deputy Managing Editor Adam Kimelman and correspondent Sean Farrell contributed to this report