In 1979 Mobekk, who competes for the Elverum IL club, won the bronze medal on the large hill at the Norwegian Ski Jumping Championships in Steinkjer . Because of this performance, he was then included in the national team for the newly created Ski Jumping World Cup . Mobekk made his first World Cup start on January 26, 1980 in Zakopane, Poland . Surprisingly, he was able to achieve 2nd place in his first competition. He was also on the podium in the second competition in Zakopane - this time third.
At the 1980 Winter Olympics and the Nordic World Ski Championships in Lake Placid , which took place at the same time , Mobekk came 24th on the normal hill and 27th on the large hill. After this rather mediocre performance, he took a year off from international competitions to train in his native Norway.
On February 13, 1981 he started again in the World Cup as part of the ski flying in Ironwood and finished 4th in the first and 9th in the second. A week later, on February 22nd in Thunder Bay, after a 7th place in the first competition the day before, he was able to jump onto the podium again with 2nd place in the second competition. He could this success again in French Saint-Nizier repeat on 28 February 1981st He finished the 1980/81 World Cup season in 9th place overall. Shortly after the end of the season he won the gold medal on the normal hill at the Norwegian Championships in Eidsvoll . In the World Cup season 1981/82 he was no longer successful. The best place was a 12th place in Štrbské Pleso at the end of the season. In 1982/83 he also started only less successfully. Only in Bischofshofen could he prove his qualities again with a 10th place. After two more top 20 placings in Lake Placid and Thunder Bay, Mobekk ended his active ski jumping career after ski flying on February 19, 1983 in Vikersund , where he again achieved a 7th place.