There's some sort of boundary/wave associated with that feature. My guess is that given where it is located, not too far from the edge of a jet entrance region, it could be an isolated gravity wave event. There appears to be a weaker impulse just behind it, particularly evident on the southern flank of that initial wave.

It's more interesting to watch than anything. Gravity waves come with perturbations in the flow fields, meaning that this event could be perturbing the flow just enough to bring some moisture into the viewable range of the water vapor sensor. That all is my educated guess, however, and not definitive.