I am generally in agreement with the philosophy of "don't book the trip before the snow is on the ground." However, in my reasearch for Powder
Magazine and my website http://bestsnow.net
I have determined that Steamboat has the best early season track record of the Colorado destination resorts. In some recent slow starting seasons when Vail was around half open at Christmas and Summit County/Front Range areas were well under that, Steamboat was about 70% open.
Wolf Creek is more likely to be 100% open, but it's much smaller, and with volatile snowfall it has no snow at all at Christmas about once a decade.