Grateful to have stumbled upon this hike. For little effort and less than two hours of exercise, the views were magnificent.

Drive to the Hwy 20 winter gate closing. Trailhead parking is labeled near the campground. 

Snow lightly covered most of the trail with patches of bare ground. Bring microspikes if you do not feel comfortable but I did not wear any traction. Enjoyed seeing so many mountains for so little effort.

I drove out to Colonial Creek Campground at the Hwy 20 closure and from there, linked together a couple of shorter day hikes: Thunder Creek, Thunder Knob, and a walk up to the Diablo Lake Overlook for approx 11 miles of hiking. I found this to be a nice way to get some reasonable miles, great views, and minimal crowds on relatively safe terrain (of course make your own judgments based on conditions when you go). All of the trails and roads in this area are snow-covered. Although I used snowshoes a couple times, at this point you shouldn't need traction or flotation to complete the trails described below. 

Driving: Hwy 20 was clear of snow until the last couple miles before the closure, where it became covered with packed snow and ice. However, they had clearly plowed recently and applied lots of sand/salt, as I had no issues with traction. There was a Toyota Corolla (sedan) at the trailhead so presumably any car can get there. 

I started with the road walk to Diablo Lake Overlook via closed Hwy 20, which was nicer than I expected. The views are great almost the entire way, and the snow-covered road is well-trodden. Early in the day, the snow was firm but not icy and I was just fine in shoes. Total for this section, 3.6 miles and approx 500 ft gain.

Then I went up Thunder Creek. For the first mile, there is an established boot path that is a little too narrow for snowshoes. When the bootpath ended, I put on my snowshoes and created a trench up to Thunder Camp. Beyond Thunder Camp there is a ski track but no boot path or snowshoe trench. Total for this section, from car to Thunder Camp roundtrip, 4 miles and minimal gain.

Last but not least I went up Thunder Knob. There is a wide, well-established trench the entire way. I've done this trail in the summer but somehow forgotten that it really does have some nice views. A super pleasant way to end the day. As noted in several places, the bridge at the beginning of the trail has been removed for the season by the park service. I found this to be a non-issue (see my pic).

Thunder Knob is a pleasant hike with incredible views for the effort. Once on the knob viewpoint, you have views SW of the Snowfield Group (Snowfield and Pyramid are particularly stunning!), east towards Jack and Ruby, north towards Sourdough, south along Colonial Creek towards the Ice Cap slam. 

The bridge is removed from the creek crossing. It's early on in the hike, beyond the large rocky wash to walk though & just as you are leaving the campsite areas. We had no trouble finding a route to keep our shoes dry, however, that'll probably change when it starts raining again tomorrow. 

There are a couple very icy patches on the trail, they are avoidable if you walk carefully on the very edge of the trail. The trail itself has frozen as pillar ice in many sections and may have air beneath so you fall into the air gap below the thin layer of trail. You'll see what I mean! :)

Great views for such a short jaunt! Not too steep and very rewarding. Wear waterproof boots this time of year as there are no bridges to cross the creek.