I live in Grand Lake. The above post is accurate. However, Mother Nature does keep her own schedule, and I have ridden as early as Halloween, and many times at Thanks Giving. The good news is we seem to be getting some early season snow here in Grand Lake, in fact, I'm waking up today (Tuesday 11/7) to about 8 fresh beautiful inches of fresh snow in town so far (it's still snowing) and the trails up high usually get at least double what town gets. So the odds of being able to ride in early December this year are better than 50% in my opinion.
In addition, it's a 'La Nina' year, which typically means we get good snow in Grand Lake. You just need to keep tabs on the conditions. Call 'On the Trail Rentals' (970 627 0171), or me, Max, at The Rapids Lodge & Restaurant (970 627 3707) for updates.
See you in early December (fingers crossed)!