In The Ring Goes South , suppose I quest successfully and have 8 progress tokens to place, but Snowdrifts is attached to the current location ( Redhorn Foothills , with 5 quest points remaining). After placing the max of 3 progress tokens on the active location, do my other 5 progress tokens spill over to the current quest?

No, I don't think so. The active location still acts as a barrier to placing progress on the quest card and since Snowdrifts is preventing you from clearing the active location, no progress can be placed on the current quest.

Ok, that's what I suspected, but wanted to confirm.