The resort would normally aim to have been open for a couple of weeks by then, however it's always unpredictable. Your lift pass covers you for Arcalis as well which normally gets snow a little earlier than Arinsal so if there isn't much here you can take the ski bus over there.
Hope this helps!
Snow record in arinsal
Thinking of booking a family ski holiday in Arinsal, arriving on 16th December 2012. What is the likeliehood of snow at that time with it being so early in the season? Thanks