Okay, I caved and decided to intercept the short line of storms shown in the radar view in my previous post. Since it was moving basically eastward I saw that I could intercept the south end of the line by heading down to the Thornburg vicinity, so that’s where I headed. The above photo was taken from a position roughly a mile east of I-95 near the Caroline/Spotsylvania county line. It shows the rain free base to the south and a gathering of scud that – at the time – looked like a nascent wallcloud. It proved not to be and after the line weakened I decided to sit out the rain in a fast food parking lot before heading north to grab dinner near Massaponax.
After I got there I looked back south and saw this:

And a closeup:
Apparently the southwestern edge was trying to organize but wound up falling apart as this feature dissipated. Never saw any identifiable rotation on radar.