Kristoffersen won both legs to win in 1min 54.87sec — 1.83sec clear of Moelgg and 2.19sec ahead of Austrian rival Marcel Hirscher.
The Norwegian also won on the difficult course last year, when he beat out Hirscher and Russia's Alexander Khoroshilov, who was fifth Sunday behind Germany's Felix Neureuther.
Kristoffersen enjoyed relatively mild race conditions which began to deteriorate thereafter, hitting the hopes of rivals including Hirscher as the fog descended to leave the latter with 1.6sec to make up on the second run.
The challenge proved too much, as it did for Frenchman Alexis Pinturault, winner of Saturday's giant slalom.
Several competitors skied out in the opening run, including Italian Stefano Gross, winner in 2015 in Adelboden, Switzerland.