Nig Alert
Similar to a (Sig Alert). A Nig Alert is a warning to the public that members of the African American community are upset over a court ruling or a jury decison in a court case that they do not agree with, thus prompting them to demonstrate or cause civil unrest.
The jury just came back with a not guilty verdict on that white deputy that was charged with roughing up the black gangbanger, someone better issue a Nig Alert.