Reports of hail over the weekend in WNY 'abnormal.' Here's why

While frozen precipitation isn’t unusual for December, reports of hail in Western New York over the weekend certainly were.

There were reports of pea-sized hail accompanying a band of storm traveling through Cattaraugus and Wyoming counties, according to National Weather Service meteorologist Steven Welch.

A local weather watcher noted small hail in Henrietta on Sunday.

The hail wasn’t large enough to register as severe, with damaging winds the most significant factor in the storm, including downed trees in Allegany County, Welch said. Still, hail typically occurs in warm season months.

“It’s not rare but it is abnormal,” Welch said.

Hail forms in thunderstorms and is solid ice generated by the storm’s updrafts, according to the National Weather Service.

Hailstorms form when raindrops are pulled to the top of thunderstorms by updrafts and freeze. The hailstones tumble back through the thunderstorms where drops of water freeze to the surface and they grow to the dimensions required to classify as hail, which is 0.2 inches in diameter.

Hail comes in two varieties: soft and hard. Soft hail is less dense, with the appearance of hardened snow, and forms in below freezing temperatures when supercooled water and cloud droplets coalesce on the hailstone surface. Hard hail forms when water drops freeze to a hailstone with outer edges above freezing, creating solid ice.

Once the hailstones acquire enough mass to overcome the thunderstorm updrafts, they fall to earth. The size of hail can vary widely and while often the size of a penny, it can grow to significant, damaging sizes.

How big can hail get?

The largest recorded hailstone in the United States was 18.6 inches in diameter and weighed 1.93 pounds, falling on July 23, 2010 in Vivian, South Dakota.

While NOAA encourages measurement and not estimation to document hail size, traditional object-to-size comparisons conjure intuitive mental images of the size.

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This article originally appeared on Rochester Democrat and Chronicle: Reports of hail over the weekend in NY 'abnormal.' Here's why