Paul & Andrew,
Thanks for the comments.
My last extended trip in the Sierras was southbound on the JMT in 2009 and was 10 days later in the year going from Yosemite to Palisade Lakes. I saw the weather morph with the elevation and the calendar. We ended up bailing back north and east over Bishop pass in a long day due to an incoming storm that ended up dumping a lot of snow at higher elevation on Oct 3rd and 4th. I have no doubt we would of been OK higher up but I would of had very cold feet in my already destroyed Salomon shoes and we would not of been able to finish in the amount of time we had. Hence this year I'm going 10 days earlier and planning a few extra days to allow for some shelter time.
Some of my clothing options (BPL Merino hoodie and MB Thermawrap) kept me plenty warm on that trip and provided some nice wetter weather insurance vs. an all down insulation approach. Part of the calculations I'll be making as I study the long range forecasts as the week progresses.
I have bail options and alternate routes all figured out and we are taking a smaller scale paper map covering most of SEKI to have all option mapped out depending on where in the trip we find ourselves. I'm also counting on getting a weather report at the Road's end ranger station as we embark on the second half of the trip onto the SHR. If it looks like bad weather we'll abort and route out using trails rather than the high route.
Some pictures from the morning of Oct 3 2009 which convinced me the weather was changing for the worse and that we needed to bail:


Evening of Oct. 3rd, 2009 from Lake Sabrina trailhead. Clouds like this in October usually only mean one thing:

Snow as seen from the East Side Oct. 4th 2009:

