The 41-year-old's second success and fourth podium from four downhills this season increased Vonn's lead in the World Cup standings and cemented her favourite status for next month's Milano Cortina Olympics.
Already the oldest World Cup winner of all time, Vonn was fastest by 0.37 of a second from Norway's Kajsa Vickhoff Lie with a run of one minute 06.24 seconds on a cold and cloudy morning with snow falling.
American Jacqueline Wiles completed the podium, 0.48 seconds slower than Vonn, on a piste considerably shortened after Friday's training was cancelled due to heavy snowfall.
"I honestly thought with my start number that I had no chance, because there's so much snow and there wasn't really a track at number six," Vonn told TNT Sports.
"I had to risk a lot with my line to really stay in the hunt. I think I executed my plan really well, I brought good intensity to my race.
"Again, I thought I had no chance so I just swung really hard. I was like 'I could be last, I could be first. I have no idea but I'm going to do my best'."
Suter back, Egger injured
As the 2010 Olympic downhill champion continued to make critics eat their words with her remarkable form after returning in 2024 following knee surgery, one rival returned and another was flown off the piste by helicopter after a nasty crash.
Reigning Olympic champion Corinne Suter made her return from a month-long injury absence after a muscle tear in a boost for Swiss hopes although she was outside the top 20 and said she still had a long way to go.
There was dismay for Austria when Magdalena Egger crashed into the side netting and, despite getting back on her feet with a bloodied nose, was put on a stretcher and taken to hospital by helicopter.
Egger, second to Vonn in St Moritz last month, lost her balance with her ski tips crossing before she went down and became tangled in the netting, leading to a 25-minute race interruption.
The weather deteriorated further after the break but Switzerland's Janine Schmitt still went from a 24th start to a career-best fifth, behind Italy's Laura Pirovano.
World champion Breezy Johnson of the United States was seventh.
Vonn leads Germany's Emma Aicher, who was sixth, by 129 points with Pirovano third.
"I'm not really a good glider so I figured I wasn't going to be great at the top," Vonn told FIS television on the podium. "Where I excel are the turns.
"I knew with all the new snow the outside track was going to be slow so I tried to stay on the inside track, on the more direct line."
While the lowered start hurt the chances of some, Vonn said her experience worked in her favour because she had previously raced a sprint from there and was one of the few who knew where to go and where to push.
The American, who is also sixth in the overall standings, now looks clear favourite to take the downhill World Cup crystal globe and, barring any drama, extend her career beyond the Olympics to the season-ending finals.
The women have a super-G on the same slope on Sunday, with Vonn again in action.