There is much to enjoy here year-round, but Winter and early Spring months are when you can get out your snowshoes, mountaineering gear, and/or skis and take advantage of this snowy wonderland. If you get a Snow Park pass (definitely get one of these, by the way - I believe California limits how much the pass-issuer will cost you, so they're not bad at $25.00 or so) you will have an excellent parking lot next to the trail. This gives you access to a paradise for Winter sports enthusiasts.

After 10am or so, I find that the parking lot exponentially fills up. Get there as early as you can.

Round Top Peak and other geological features, like Elephant Back (which is aptly named), tower above the relatively flat surroundings, this gives you the freedom to cross country and explore around. Kirkwood, CA and the Mokelumne Wilderness are known for high levels of precipitation. I was here recently (mid-April) and it is still dumped on. Be courteous and follow "snow etiquette and traditions", in other words don't be like me and trample parts of ski tracks and get called out for it. Duh!