When Western New York gets hail from a thunderstorm, typically it is in the late spring or early summer.  When that happens it is usually pea-size or penny-size hail. That hail size is typically not a major impact for the average person. Unfortunately, that is not always the case in other portions of the country. We had pictures earlier this week in Texas where they had hail the size of tennis balls. This large hail took out windows and fences and can be a significant hazard to people and livestock.

The high-risk area for this weather was the middle of the country, from Texas to Nebraska. No doubt there was a threat of damaging straight-line winds and isolated tornadoes.  But the highest probability for damage was large hail, which is considered to be 2 inches in diameter or greater. Over the next 24 hours that threat level then moved into the upper Mississippi Valley, not far from the City of Chicago. 

Why does this hail get so large? This answer comes when examining a cumulonimbus cloud and the intensity of a thunderstorm. Specifically, it is the intensity of the updraft in the thunderstorm cell that is of most concern. A piece of hail is like an onion that has layers of accumulating ice. This process of ice accumulation is called accretion. The wind in the updraft is driving this storm as it acts like a vacuum and essentially suspends that chunk of ice for a greater and greater period of time.  The size of the hail is directly proportional to the speed of the updraft. When we see the chunks of hail that are the size of baseballs or oranges, the updraft (or vertical wind speeds) can reach 80 or 90 miles per hour. This usually only happens in a thunderstorm cell that is reaching 60,000 or 70,000 feet in height.  Damage is almost inevitable with these storms.

Not to sound trite, but this is the time for duck-and-cover no matter where you live .