Anytime you experience an over-rev condition that is thought to be caused by moisture on the clutch sheaves, you will want to inspect the belly pan area in front of the primary clutch to see if there are any places where snow is getting into the clutch compartment. For example, many sleds have small plastic caps that pop in and out of the belly pan in this area (to provide service access to bolts and fasteners). If one of these caps has popped out of place, this opens up a hold for snow to get in, and when it contacts warm clutches it turns to water, and the belt slips, potentially causing an engine over-rev condition. Make sure to replace any missing caps in the shock tower and belly pan areas.
Often times there will simply be gaps around the belly pan where it contacts the chassis, and these provide a path for snow to enter as well. Seal these up with silicone to keep the snow out.