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Large hail in the mountains: Possible, but not common

Large hail, one inch or bigger, is very rare in the mountains because the high country lacks two key ingredients for large hail formation.

FAIRPLAY, Colo. — The hail in Colorado this year has been huge. Baseball-size hail was reported for the third time this season on Saturday, and ping-pong-ball to golf-ball-size hail has been reported on 10 different days.

There was also a crazy hail scene over the weekend – hail at 10,000 feet near Fairplay, and lots of it. It was mostly nickel and dime size hail, which doesn’t happen too often in the mountains, but there was also a report of one-inch hail, which is very unusual.

Large hail, one inch or bigger, is very rare in the mountains because the high country lacks two key ingredients for large hail formation: low-level moisture and rotating updrafts.

To create large hail, a storm needs ample moisture near the ground level. The mountain ranges form a blockade that usually prevents moist air from reaching too far up in elevation.

A storm also needs a strong rotating updraft to suspend hailstones long enough to grow big. Thunderstorms with rotating updrafts are known as supercells. But the peaks, ridges and canyons in the mountains create chaotic wind patterns that usually prevent rotating updrafts.

The most common place to find mountain supercells is in South Park. Low-level moisture can find its way through a gap in the mountains on the south side of Pikes Peak, and the relatively flat terrain in that area allows rotating updrafts enough time to organize.

Credit: KUSA

There have been 24 reports of hail larger than one inch in Park County since 1950. That's the most of any mountain county. Saturday’s large hail report was the first there in three years. Baseball-size hail was reported there in 1985 and again in 2018. 

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