UPDATE: The National Weather Service (NWS) has extended the flash flood warning for northern Boone County until 1:03 pm. HERE IS OUR ORIGINAL STORY: Centralia, Hallsville, Harrisburg, Sturgeon and all of northern Boone County remain under a flash flood warning until 7:03 this (Tuesday) morning, due to heavy rain overnight. National Weather Service (NWS) St. Louis …