A follow-up:
I had the tire replaced yesterday - $180 out the door (zounds!) Wasn't it not too long ago that one could replace a set of 4 tires for that amount?
The tire guy showed me the culprit - a piece of metal about half the size of a box cutter blade -
in the tread. He said that created the air leak, the loss of air caused the tire to heat, which caused the weakest part of the tire to explode - the side wall - it sure did do that !
Yes, a good Thanksgiving, in that she wasn't hurt..