I was actually suggesting a couple 2-3 day trips, not day trips. Basically, you arrive...if the forecast looks good then do trip one. Then come back in, and if it still looks good then do trip two, otherwise day trip as long as things are OK. As I noted, the daytime weather is
often nice in October, but snow (enough to pose problems and temporarily close roads) does happen. Nights...yeah, expect low 20s or upper teens. Hopefully it'll be better, but don't expect above freezing.
Another consideration is that non-desert areas of the west (so you're not carrying all your water - impractical for a 6 day trip!) other than the Sierra, which are large enough to sustain a 6 day backpack, are likely to be even more problematic than the Sierra for a 6 day trip. Grand Canyon is just about the only exception I can think of.
A few thoughts...
The aspens should be turning color on the east side of the Sierra during your timeframe. Thus, maybe one trip (the later one, if you're OK with the two-trip suggestion) could start on the east side. Leavitt Meadows up towards Fremont Lake, in the Hoover Wilderness, from CA-108 is an option. June Lake area - CA-158 up towards Gem Lake has nice color (then up into the pines). A beautiful one-night trip might be from Convict Lake (just south of Mammoth) towards Dorothy Lake. Two years ago I hiked up McGee Creek in October (just south of Convict...) - lots of stuff up there. Twin Lakes (between Bridgeport and Lee Vining) is another starting point with good fall color chances.
Your last day is October 16, and overnight parking is disallowed along the Tioga Road after October 15 - sadly inconvenient, unless the trip is split and the Yosemite portion is done first.
Before I type more words...are there more specific interests you may have? Alpine scenery and lakes? Color? One thing to consider is that only the largest streams may be flowing by then, we're in the third year of a severe drought, so by October water access will be a consideration, suggesting lakes may need to be part of the itinerary.
EDIT: October 15 tends to be a "magic date" for another reason. CA-108 and the Tioga Road (CA-120) (and others) close for the winter. If a big storm dumps on the passes before October 15 CalTrans and NPS will try to plow them - though it may take a few days. After October 15 - the sun needs to take care of, at least, most of it.
Edited 2 time(s). Last edit at 08/07/2014 06:25PM by ttilley.