The asteroid KW4 1999 will be passing by Earth from 5/24-5/27 at a distance of 3,000,000 miles away.  In other words, we should survive this flyby with no problems; however, this asteroid is classified as a potential hazard.  It's about a mile wide and traveling at about 48,000 MPH with its own moon in tow.  Definitely a showstopper for life as we know it on Earth were it on a collision course.  Again, we're in no danger of that scenario this time around.

As far as seeing it, that's a tough one.  It is possible to view with an amatuer telescope, but here in Billings, we'll likely have substantial cloud cover when it's at its closest distance tomorrow.