Writing a novel synopsis

I'm working on my novel synopsis this weekend. I have to admit, I'm a little stressed about it.

I've never written one before and, since I haven't finished the manuscript yet, it's the uncertainty about the scenes I haven't yet written that concerns me. I've introduced characters I'm not sure will survive later drafts of the novel and, although I have a general sense of the novel's ending, I'm still up in the air about some sub-plots, their development and resolution.

I'm preparing to send the first 100 pages to a developmental editor. I'm in desperate need of feedback on the draft so far. She's asked for a synopsis, as well.

Yet, I'm convinced this exercise is a good thing. It'll force me to 1) decide the sequence of events in the second half of the book, 2) address nagging questions I have about some sub-plots, and 3) provide motivation to pull me through the remainder of the first draft process. If you've read my recent posts, I'm in need of motivation. Or, maybe, its feedback and validation I need. Whichever, I'm excited to have the opportunity to have someone whose opinion I value read my work.