The Swede took her second victory of the season to stretch her lead over Italy's Silvia Bertagna to 73 points, after Dahlstrom beat her rival into second place in Norway.
With just five riders making the final, Zuzana Stromkova failed to start the showdown meaning it was just a four-way contest for the medals.
Dahlstrom put down scores of 83.6 and 87.6 for an overall total of 171.2, which was good enough to beat Bertagna by 11.2 points.
Home favourite Tora Johansen picked up the remaining medal with a score of 121.6, just edging Germany's Kea Kuehnel into third place after she could only manage 119.6.
In the men's event, Christian Nummedal won his first big air World Cup of the season as he moved up to third in the overall standings.
The Norwegian scored 177.8 to beat his compatriot Birk Ruud by 7.6 points and take the win on his home slope.
And it was a Norwegian one-two-three after Ferdinand Dahl rounded out the home podium with a score of 160.8.
Sweden's Henrik Harlaut still leads the overall standings with 349 points, ahead of Switzerland's Kai Mahler on 240.
The circuit continues on Saturday with another run in Norway. Sportsbeat 2017
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