They discovered it monday night, not much time to evacuate a whole major city. I expect that the politicians would want to sit on it for a day or two, to figure out what they are going to do, but if it was targeted towards a major city, I'm sure it would leak out to the media and civilians.
I would *guess* that an impact of this size (30 meters on impact) would possibly be survivable outside of 10 miles, depending on natural protection, like hills, mountains, etc, and if a warning was given.
With a simple warning, one outside of the total death and destruction zone could at least find some easy, low lying protection and at least try and cover one self from the massive debris that would undoubltly rain down for several minutes, or more. It would be unbelieveable to witness an event like this from about 100 miles away. Even then, you would want a hole to quickly jump into after taking a fast glimpse.