The victory makes Shiffrin only the fourth female skier to win world titles in four different disciplines. Last month, she broke Lindsey Vonn's women's record of 82 World Cup wins.
Hilaree Nelson, 49, was skiing down from the summit of 26,775-foot Mount Manaslu on Monday when she fell off the mountain
"Coming back out and getting the chance to race again was just the perfect thing to do, actually," Shiffrin said. She had failed to finish qualifying runs in two events earlier this week.
Ski areas are seeing record sales of season passes as people look for outdoor exercise this winter. Most are requiring masks, limiting lodge use, and making people put their boots on at their cars.