Before slowly elongating into its “white snake” stage, the Prospect Valley tornado exhibited some behavior that was uncommon in my experience for a tornado not rotating particularly fast above the surface. For once, the fuzzy, ragged cloud material along the near left “edge” of the visible funnel were forming in place and rising nearly vertically, connecting with the main condensation tube. This signified air being drawn vertically from outside the vortex, many hundreds of feet above the surface. Also, a short, narrow accessory vortex (which was spinning rather rapidly!) can be seen off the near upper-left edge of the main tube, its visual bottom directly above the top of the leftmost utility pole. This meant both funnels were pointed at electric poles, from my perspective. The only other tornadoes I have seen with well-defined accessory vortices were certifiably violent; this was not. I propose that the near-tornadic flow enhancement combined with winds of the ambient mesocyclonic updraft to stretch some pre-existing vorticity at that level in order to form the visible secondary funnel, which did not connected to the main tornado (unless at a position hidden in the ambient cloud mass above), and which only lasted a few more seconds.
4 S Prospect Valley CO (19 Jun 18) Looking NNE
40.0152, -104.4178