Yarnold, who won World Championship bronze in Lake Placid in 2012, ended the four runs on the German track with a total time of 4:04.06minutes.
That gave her a 2.82seconds cushion over Donna Creighton with Laura Deas 3.50 adrift in total with Rose McGrandle disqualified at the halfway stage.
Meanwhile Smith leapfrogged Dominic Parsons into pole position upon the completion of the four men's runs with his overall time standing at 3:56.67.
Parsons placed second, 1.14 behind, with three-time Olympian Kristan Bromley third, David Swift fourth and Vancouver 2010 Olympian Adam Pengilly fifth.
Britain will field three men and three women on the World Cup circuit this season with reigning world champion Shelley Rudman earning pre-selection.
However who will slide on the World Cup circuit and who won't isn't decided solely on placing with a selection meeting to take place to determine the athletes chosen.
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- Donna Creighton