A line of supercell thunderstorms were move E/SE across Lawrence, Morgan, Winston, and Cullman counties. Radar shows a storm developing immediately ahead of these storms and it was moving E/NE. As this storm began to interact and eventually merge with the line of supercells, the updraft intensified. Very strong vertical motions were noted on radar with this storm. These strong updrafts allowed for very large hailstones to remain suspended aloft, allowing for additional growth. By the time the hailstones started to fall they were the size of baseballs to as big as grapefruits. One of the largest hailstones found was by Craig Mann a reporter with The Cullman Tribune. A photo of Craig with the hailstone can be found below. He preserved this very large hailstone in his freezer. On Wednesday March 21st, 2018 meteorologists with the NWS Huntsville forecast office met with Craig Mann to take an official measurement of the hail.

Aided by the Insurance Institute for Business and Home Safety, who conducted a laser scan analysis of the stone, the hailstone measured 5.38 inches in peak width, weighed 9.8 ounces, and had a circumference of 13.75 inches. Previously there was not an Alabama state record for largest hailstone. However, NWS Huntsville had this certified with the National Centers for Environmental Information (NCEI) and they have accepted and certified this as the largest hailstone on record for Alabama. You can read the press release submitted by John Christy, the State of Alabama Climatologist, here and view the report from the State Climate Extremes Committee here.

For reference, the largest hailstone ever recorded fell on July 23rd, 2010 in Vivian, South Dakota. It measured 8.0 inches in diameter, 18.62 inches in circumference and weighed 1.93 pounds.