Considering that I'm planning to run in the exact same weather (I'll be in Denver this weekend) on Saturday, I opt for capris. That's what I'll be wearing. Long tights would be too warm for me, even at those temps. I don't wear shorts for long runs due to potential chaffing, so that leaves capris as the best option.

What I'm going to wear on top is a mystery. When I looked at the weather when packing, the ran chance was only 10%, so I didn't bring ANY rain gear with me!