Even with uncertain weather, it's a great time to go and my favorite time of year to go! There's no humidity at all and the crowds are probably at their lowest (except around MLK and President's day).
In January of 2003, there was a cold snap. That night it dipped down to 28 degrees! The next morning we heard one of the CM's at the Wilderness Lodge bus stop say it hadn't gotten above 35 degrees yet! We froze that day because none of us were prepared with heavy winter coats, hats or mittens! Pack for any kind of weather to be on the safe side.