ApproachFrom Highway 89, turn onto Fallen Leaf Road. This is about 1 mile toward South Lake Tahoe from the turn-off which says, "Tallac trailhead". Follow the road (horribly pitted dirt for a mile or so in early season) to its end at Lily Lake. Follow the well-signed Glen Alpine Trail, which is a heinous surface of chickenheads for the first mile or so.
Route DescriptionThis photo shows the Glen Alpine Trail in relation to other routes up the mountain.
For the first couple miles of the 5.4 to the summit, the trail follows first the drainage of Glen Alpine Creek, and then climbs the southwest slopes of Cathedral Peak. At roughly mile 3, the trail meets up with the Pacific Crest Trail, and splits off at Gilmore Lake, at mile 4 and 8400' elevation. From the Lake, the hike is an easy and steady 1300' climb.
Warning: during the winter, route-finding becomes quite difficult. In the trees below Gilmore Lake, snow covers the trail well into late spring. Beware of some cliffs in this region. I got lost here once in May, and ended up doing some class 3 scrambling over some pretty loose, snow-covered rocks. A GPS might come in handy if you would like to avoid any adventures.
South Slopes Ski Descent:
The book by Paul Richins, Jr. lists a descent of Tallac's south slopes as a classic beginner backcountry trip. I have not skied it, but I agree with the assessment. The south slopes offer everything from very mild open slopes to beautiful tree skiing. If you retrace your steps along the trail, you will have trees for the bottom 900' of the 1300' descent to Gilmore Lake. Another possibility is to roughly follow the open slopes near the Cathedral Lake trail (Green route on this map.) and take that trail down the mountain. To do this, you would have to use a car shuttle or find the use trail that takes you to the Stanford Sierra Camp on Fallen Leaf Lake and make your way back to the Lily Lake trailhead. Warning: Watch out for the cliffs on the south side of Cathedral Lake!