Obviously, this route can also be used in the summer months; however, the Mack's Canyon route is more aesthetic and accessed almost as easily in the summer.
The starting point is around 8300 feet. The route involves only about 1900 feet of gain and 5 miles or so roundtrip. I describe the route as "Most of a day" due to the snow travel, etc.
While traveling on the Lee Canyon Road toward the ski resort, you will come to an obvious snow play area (a large, open meadowy area) on the right at around mile 16. The Sisters is the obvious mountain towering above the snow play area. Park along the road.
Walk back down the road about 1/4 mile or less to the entrance to a campground on the same side of the road as The Sisters. Enter the campground and follow the road (the campground is closed in winter and the road is not plowed) for a half mile or so. Along the way, you will pass a few ridges and some small drainages. At around the 1/2 mile mark, pick a route up one of the ridges on the right and start up.
a route overview photo.
While traveling up the ridge of your choice, The Sisters will be north/northeast of you, and obvious. Although it may be tempting to head straight for the mountain, trend westward a little to avoid cliffs and rocky obstacles, and ultimately aim for an east-west ridge heading up to the mountain. Much of the route is in shade and will have deep snow.
Once you gain the west ridge of the mountain, head east toward an obvious wide chute area in between Middle Sister (on the left) and South Sister (on the right). As you ascend, take a minute to enjoy the Bristlecone Pines along the route.
Toward the top of the chute, the angle sharpens to around 50 degrees. At this point, you can either stay to the left side of the chute and negotiate iced-over rock or move a little to the right and work your way upward through deep snow. As you approach the saddle between Middle and South Sister at the top of the chute, admire the excellent grove of gnarled Bristlecones there.
From the saddle, South Sister is a quick and easy jaunt to the right. Middle Sister is more interesting. To get to the summit of Middle Sister, approach a class 3 chimney of mixed snow/ice/rock on the north side of the saddle and start climbing. The chimney has little exposure. The chimney's only about 20 feet, and at the top is an exposed snowy ledge about 3 feet wide.
Once on the snowy ledge, you are only about 15 vertical feet below the summit. Traverse to the right on a steep and exposed snowy ramp around the rock on your left and work your way up the last few feet to the knife-edge summit.
The summit is generally snowy (remember, I'm describing the Winter Route), and most recently while I was there, there was a small summit cornice to cross on the 100 foot or so traverse to the actual highpoint. The exposure along the summit ridge is fairly substantial, but more an issue of fear than genuine threat.
Although the actual summit highpoint is only a few inches or so higher than the top of the snowy ramp I just described, this is where the summit register is located.
To descend, retrace your steps.
Typical winter climbing gear. Ropes are necessary only for those particularly uncomfortable with the steep, exposed snow above the chimney and with the chimney itself.
If you have information about this route that doesn't pertain to any of the other sections, please add it here.