after thinking about it abit more, I might not take the risk, but I doubt CO could make me spend money on a hotel overnight and wait until the morning to fly if I "missed" the flight by accident. They might offer to put me on Amtrak (which is OK, since there is no proof of me actually taking the train in that case), which is what they did for me after the winter snow storm disaster earlier in the year.

I will look at more comments as they get posted, but I think I might take the DCA flight and then drive back the next morning.