A fast-moving thunderstorm dumped heavy rain and very large hail across metro Omaha, Nebraska late June 29, 2017. Reports mention hail of many sizes left a widespread trail of damage – shattered windshields, pierced skylights, and damaged roofs.

According to the Omaha World-Herald, hailstorms came in waves, first across central Omaha, Benson and midtown, and on to the east into Council Bluffs. Then hail moved across southwest Omaha and Sarpy County and, finally, Glenwood and others points in southwest Iowa. Most of the hail reported ranged from marble- to egg-sized.

Barrett’s Benson neighborhood took on some of the largest hailstones, up to baseball-sized and larger. Barrett measured a hailstone that was 9.5 cm (3.75 inches) in diameter.

The two supercell storms that delivered the barrage of hail intensified as they reached the Omaha metro because they encountered what is known as the nocturnal low level jet, said Becky Kern, a NWS meteorologist. A summertime phenomenon in the Great Plains, the low level jet is a stream of warm, moist air rushing northward from the Gulf of Mexico. It flows in at about 915 – 1500 m (3 000 to 5 000 feet) and provides lift to the atmosphere. As the storms arrived, they encountered this warm, rising air, which gave the storms “lift,” a crucial ingredient to severe weather and hail.

“One indication of how powerful the updrafts were with these storms is the heights of their tops,” Kern said. These storms rose to 14.3 km (47 000 feet).

“The good news with this storm was wind – it was negligible,” she said. “Had there been strong winds with these large hail stones, homes would have been badly damaged, with holes in siding and windows.”

The storms then rolled into Iowa with the same intensity and hail just as large.

H/t reader kevin a.