Just a head's up. I noticed these are on sale at Crappy Tire for $40. I bought 2 of them, as I am moving to Alberta.
Here's what they look like.
I dubiously bought one, expecting it to, well, be cheap and stupid. I was pleasantly surprised. The seams are taped, it's strong, it folds up very small, it's fairly water resistant. I actually bought another, and the two fit side by side on the roof of my Jeep Cherokee.
The downsides are they are not secure, theftwise, and they would probably scratch the top of your car (my poor cherokee has so many brush scratches it hardly matters).
They can handle 3 backbacks easily. They do need some sort of rack, although apparently they work with racks that don't have crossbars.
I don't work for Thule or Crappy Tire, I am just impressed with the price and product.