RALEIGH, N.C. (WNCN) — The National Weather Service Raleigh has issued a flood watch for several counties across central North Carolina Thursday. A flood watch was issued for Person, Alamance, Orange, Durham, Chatham, Wake, Johnston, Moore, Lee, Harnett, Hoke, Cumberland and Sampson Counties. Helene weakens to tropical storm; tornado, flooding threat still present in the Carolinas The watch went into effect at 6 p.m. Thursday and is expected to last until Friday afternoon, according to the NWS. Expected impacts include excessive runoff that will result in flooding rivers, creeks, streams and other flood-prone locations. Much of central N.C. is susceptible to flash flooding during significant periods of rainfall. A tornado watch is also in effect until 8 a.m. Friday for a few North Carolina counties south of Raleigh. These include Sampson, Cumberland and Hoke counties in CBS 17's viewership area. Earlier Thursday afternoon, NWS Raleigh issued a tornado warning for three counties in central North Carolina. The warning was issued at 5:51 p.m. for Granville, north central Wake and Durham counties and was in effect until 6:30 p.m. A previous warning for Wake County was also in effect until 6 p.m. According to forecasters, "a severe thunderstorm capable of producing a tornado was located over Raleigh, moving north at 20 mph." Those in tornado warning areas should take cover, as flying debris could cause damage to buildings and vehicles.