24-year-old Skaanes - with a 20th place in the World Cup as the best - broke the pre-favorites uphill in Norwegian Top Sports Week and crossed the finish line three seconds ahead of Lina Korsgren.
Norway's Emelie Fleten finished third, another 25 seconds behind.
For Marit Björgen and Britta Johansson Norgren it was even harder.
They ran in as four and five respectively - 43 and 53 seconds after winning Skaanes.