Derecho is a bow echo then, ok.
I need to look up the lit on those, I've never understood the mechanism properly. Looks like a radar version of a bird's eye view of a downburst, but sustains too long for that.
Yes, downbursts and microbursts and bow echos are ugly things. Trees overgrow with time, and poor construction accumulates, and buildings deteriorate, until what I call a "limiting wind" comes through, and knocks down everything within the limits of it's velocity, leaving most remaining tested to that speed, but not to a higher speed.
60 mph seems to be a lower limit for this type of thing, so the longer an area goes without 60 mph plus winds, the more the damage when that level winds does come through.
If an area goes a long time without such levels of severity, and then an 80 mph wind comes along, look out.
On top of this are eddies, gust currents, and in areas with terrain or commercial building restrictions to boudndary layer (ground) flow, you get funnel effects which stack on top of all the above.
Hoping St. Lou comes through ok, downed buildings indicate significant winds, with the early "fog of war" possibly restricting reports of even greater damage.
This system has a huge amount of potential energy, so folks east of St. Lou need to keep their eyes open tomorrow, Illinois, Michigan, Indiana, Kentucky, Tennessee, Ohio, etc.
One of the reasons for the impression that trailer parks get hit with tornadoes constantly is that much of the time when they're damaged it's not from tornadoes - however, the residents of the park fervently believe it was a tornado and the media does nothing to dispute the victims.
By the time NWS survey teams come through a couple days later it's no longer in the news and people tend not to notice when it's proclaimed to be damage from straight line winds.