Thanks for the replies, guys!
I setup PingPlotter to show pings for hop 4 (the first hop that shows lag) and hop 13 (the final hop at Google). Here is a snapshot of the data taken during the middle of last night's lag window: »i.imgur.com/VTdc8oY.png
Also, here are my signals: »i.imgur.com/285VYIj.png
(though I just took this, outside of my lag window -- I can post them again during tonight's lag, if you suspect they'd be any different)
And the reason why I wasn't displaying the destination ping before, was that TWC has said in the past that they can't control anything beyond their routers, so I wanted to just highlight the fact that it appears to be happening on their hops. But good to know.