I had *thought* that I was doing okay, roof-wise -- a small leak in the bay window due to the ice dam there, but no other signs of trouble. I knew that there were a few ice dams elsewhere, but thought that they weren't causing too much melt. I *have* been worried about roof collapse, but not too much about leakage, since there is no sign of dripping through the roof itself. Naive me.
I just discovered that the ceiling of the guest bedroom is totally trashed -- I walked in there to put something away, found the floor wet, a steady single drop dripping, and a mild but dangerous bulge in the ceiling. So I followed the advice from the TV yesterday: I put a (big) bucket in the desired location, grabbed an awl, and punched several holes in the drywall. A good gallon came through in the first couple of minutes.
There *still* is no apparent drip in the attic, so my best guess is that the ice dam is causing leakage right at the edge of the house, down by the soffits -- instead of going over the edge, it's flowing inward, and finally pooling about five feet into the room.
Pain in the tuchus. The ceiling is clearly a loss, so for now I'm just punching holes as needed and accepting that I'll need to replace it come spring. In the meantime, I dearly hope nothing else breaks horribly...