I vote early to Mid March, lots of snow by then, and most rocks and stumps are well buried by then, with plenty of Pow to be had. April is hit or miss, although as cuzzinolaf stated, the past few seasons, the Snowys have been awesome in April, last year was stellar, we received over 3 feet the day we arrived. The only drawback to April riding in Wyoming, in April, they stop grooming the trails on April First, but then again, we don't go there to ride trails, but it can make getting from point A to point B a but rough if their is heavy traffic. Also as a side note, Togwotee Mtn Lodge typically Scales back their opperations after April First, the Resturant is Closed, so lodging is on the Cabins only, and you must bring/cook your own meals, but the traffic is light, and if you hit it right, you can have great snow.