Hail up to the size of baseballs fell on the west side of Spartanburg, South Carolina, on 20 August 1999.

Author's Note: The following report has not been subjected to the scientific peer review process.

Several classic supercell thunderstorms moved southeast across Upstate 
South Carolina and the southern North Carolina Mountains Friday, 20 August 
1999.  One of the stronger storms moved directly over the city of 
Spartanburg, South Carolina.  Fortunately no tornadoes were spawned, likely 
due to light winds in the lower few thousand feet of the atmosphere, and the 
lack of any pre-existing boundaries.  However, tremendous hail was produced, 
as evidenced by the above picture, taken on the west side of Spartanburg 
shortly after the storms moved through.  Weather radar showed a classic 
supercell with a hook-shaped appendage when it was several miles south of 
the city, shown below.

Base reflectivity from the KGSP radar at 2203 UTC on 20 August 1999.  
Elevation scans are at 0.5 degrees (upper left), 1.5 degrees (upper right), 
2.4 degrees (lower left), and 3.4 degrees (lower right). Click on image 
to enlarge.