From the Kirk Bauer FAQ:
12. Snowdrifts wrote:
You don't travel to Caradhras (D 15), it just becomes your active location. After reaching 11 tokens on this card, any remaining unplaced progress tokens will then be placed on Caradhras (D 15).
Interestingly but not related to your question, from FFG FAQ:
Q: If Caradhras (DD 15) is in my victory display when
I complete stage 2 of The Redhorn Gate, will it become
the active location even though it is not in play?
A: Yes. You will remove Caradhras from your victory
display and put it back into play as the active location.
Cards in the victory display are not removed from the
game and can still be referenced by effects. If players
get too far ahead of themselves via card effects, they’ll
find a return journey is necessary!