This is a winter ascent. So instead of traversing an avalanche prone slope to over Sourdough Creek and go to Sourdough from the east (or go to the Lookout from west), we followed the ridge up and go to Sourdough from the west. The branching off point is around 4200~4300', a large flat-ish area that one can camp.
Continue up the ridge, you'll reach a "rock arrete", which may post problem for some.
Above it, it's quite easy.
All along, no avalanche danger at all.
We also went west to Peak 6308. Didn't have enough energy or time to go to Stetattle Ridge, which may take an extra hour.
The first 2 miles or so on the trail is very hot.
Altogether ~5900' elevation gain, 11.5 miles.