Snow : it's good for something ( showing the aero wake )
 

While researching a new vehicle for my friend in Canada, my eyes zeroed in on the wake that is visible at 4:00 - 4:01 in the video on this page :

AWD Showdown: Subaru Forester vs. Honda CR-V vs. Toyota RAV4 - Consumer Reports Video Hub

This is nearly as good as the smoke used in wind tunnels ! You can clearly see the air as it spills off the roof and follows the curve that you would see if you laid a template over the roofline.
It also shows the vortex back there.

Too bad it's only a second of the video.

Maybe you mean at 0:26s? 4:00s is a Consumer Reports logo.

With a thin layer of snerodynamics on the back.