I used the standard antenna outside on the Velux roof window for months after I got my RB, it didn't seem to come to any harm. I stand it outside on the window ledge in the rain every now and then, and it's fine.
One of the biggest killers of any antenna mounted outside is water getting into the co-ax as it just sucks it up like a sponge. That and corrosion causing a lack of electrical contact between the antenna and the cable.