Riesch, the overall cup points leader, came in ahead of Austrian Kathrin Zettel, who was second, and Finland's Tanja Poutiainen who came in third.
Lindsey Vonn of Vail, Colo., finished in a fourth-place tie with Anja Paerson of Sweden.
Riesch is 85 points ahead of Poutiainen in the overall points race.
Rosie O'Donnell unveils nearly 50-pound weight loss
Administration delays decision on Keystone XL once more