Already answered, but I'm pretty sure it was lack of coolant. I put a bottle of water wetter and about a quart of water and it seems to be staying cool. Honestly, I haven't been doing much driving and right now I'm halfway across the country, but I'm pretty sure that solved the problem. I assume that I have a VERY slow leak and will just continue to monitor the situation. If I get back from Las Vegas and find out that it is not fixed, I will keep you guys updated.

Thanks for all the advice and diagnosis.