This started at 12:30 pm local time (EDT), and is still going at about 8:00 pm local. The interval between the "carriers" is about 30-31 kHz through all of HF, at least. I looked at 31 kHz and saw nothing.
Reception is still fine between the QRM, and you can see I am tuned to a SSB signal.
If I disconnect my antenna the QRM disappears, but with just a 12 inch piece of wire for an antenna, I get it (along with a few very strong stations). So I think that rules out my receiver but makes it local.
Next step is to cut power in my house (maybe I leave one circuit on for my rig, or if I am feeling energetic I could run it off a 12 voltage battery). I live in a suburban housing, so plenty of opportunities for nearby noise sources.
The link below is to a picture of the spectrum display on my rig.
https://imgur.com/Ttjm9kzBTW, I have seen that "swishing" on the spectrum display before and always wondered what it was (I'm a new ham). But I have never had these very strong "QRM harmonic carriers" before.