Pietilae-Holmer was nine-hundredths of a second faster than Austrian Nicole Hosp and 14-hundredths quicker than Slovenia’s Tina Maze.
The Swede, who won world championship silver in the giant slalom at Åre in 2007, timed in 53.86sec.
The second leg was scheduled to start at 20:00 GMT and the field was tightly bunched.
Finland’s Tanja Poutiainen was in fourth place, but only 20-hundredths off the lead.
Austrian Marlies Schild, who won the first slalom of the season at Levi, Finland, started in bib No. 1 and promptly skied over the first gate, a rare mistake for a skier of her calibre.
Germany’s Maria Riesch, seventh after the first leg, had a chance to replace compatriot Viktoria Rebensburg atop the World Cup overall standings with a solid showing in the second run.