This is the wind profile from the SPC Convective Outlook and, as you can tell, the 30% region is over a good chunk of Middle TN. The only areas left out of it are in Northern Mid. TN and the Plateau counties. A strong MCS (could be a defined a derecho as well) is marching across eastern AR at this hour and will affect areas, mainly in SW Middle TN later this evening. But all of Middle TN needs to be on the lookout for this as we are in a Slight risk. Where you see the 45% hatched area...that is a MDT risk zone.