Asteroid 1999 KW4 is not going hit Earth tomorrow. Don't believe me, though. Here's some good resources and tools to fact-check for yourself.
Summary Small asteroids are faint and hard to detect. Many times they are not spotted until they approach Earth's orbit very closely. A newly discovered asteroid named 2017 OM1 is a good example
Asteroid impacts are one type natural disaster that we can realistically prevent, and it's important to continuing pushing for funding and prioritizing these efforts through NASA and across the world.
(Updated 23 Jan 2019) What do we need to do to deflect an asteroid that's going to hit Earth? It's not very simple and it requires decades of intense study and continued technological