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The 37-year-old former world super-G champion and Wengen winner in 2015 timed 2min 31.50sec down the 4.4km-long Lauberhorn course, the longest on the World Cup circuit.
Italian Peter Fill was second fastest, at 0.23sec, with Switzerland's Beat Feuz in third (+0.34sec).
A first training run on Tuesday was cancelled because of high winds and snow.
There is one more downhill training run scheduled for Thursday before Friday's combined (downhill followed by a slalom), with a downhill set for Saturday and a slalom rounding off competition on Sunday.