Northern Oil & Gas' chairman of the board has resigned, while another company director, Bahram Akradi, has been appointed "Lead Independent Director."

Rich Weber, who has been chairman since January 2016, resigned from Northern Oil's board Monday to focus more time on his role as CEO and chairman of PennEnergy Resources, according to a filing with federal securities regulators.

PennEnergy is an oil and gas company particularly active in Pennsylvania. Weber had been a director at Minnetonka-based Northern Oil since August 2011.

In a press statement, Akradi said Northern Oil "wishes to thank Rich for his tireless service as chairman."

Akradi, CEO of Chanhassen-based Life Time Fitness, is Northern Oil's second largest shareholder with an approximately 10 percent stake. He was appointed to Northern Oil's board in July.

Northern Oil, which invests in leases and drilling projects in North Dakota's oil fields, has been battered by the downturn in the nation's oil industry since late 2014.

Still, the company Wednesday raised expectations for the fourth quarter, upping its oil production guidance.

Northern Oil's stock is trading around $1.70. Its 52-week low is 63 cents; its high, $4.