The meteorology behind the small hail that blanketed Meridian, Idaho like snow
On Friday evening, a severe thunderstorm moved through the Boise area in southwest Idaho. This storm brought damaging wind that blew a few trees over but the bigger headline was small hail that blanketed nearby Meridian, Idaho in a way that looked like it was several inches of snow.
These types of thunderstorm events are fairly rare in any one location but a few of them occur in the United States and Canada every year. A unique meteorological environment is required to form them including the freezing level, moisture, and wind.
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Model estimated upper level conditions in Meridian, Idaho at 21:00 MT Friday. (Ingalls Weather)Using model data from around 21:00 MT Friday (when the storm hit), a few of these features stand out. The freezing level was around 10,000 feet (3,000 meters) and above that was a deep layer between -10 and -30ºC across several thousand feet. This is the layer where hail develops. The deeper and colder it is, the better a storm can manufacture hail.
The real key was the shape of the storm’s fuel, though, not just the amount. Meteorologists measure a storm’s potential energy as CAPE (Convective Available Potential Energy) which essentially tells how hard a rising bubble of air gets pushed upward. What matters for hail isn’t just how much CAPE there is but at what altitude it’s distributed through the atmosphere. It is measured in joules per kilogram (j/kg).
Weather radar image showing the severe thunderstorm moving through Meridian, Idaho at 20:57 Friday. mPING reports and severe thunderstorm warnings shown. (RadarScope)Picture two storms with the same amount of energy but one has it packed into a short, intense burst down low while the other has it stretched thin over a tall vertical column. The first forms a violent updraft that throws a few stones high to grow them into large, damaging hail. The second, which forecasters nickname “tall skinny CAPE”, is gentler.
The Meridian storm had tall skinny CAPE. The energy was modest and spread across a deep layer in the atmosphere, so the updraft was steady rather than explosive. Instead of building a handful of big stones, it acted like a slow ice factory by lofting countless water droplets fast enough to freeze and grow. This produced an enormous number of tiny stones that fell together as a dense, slushy curtain.
The last ingredient was wind. The profile showed winds turning and strengthening steadily with height. This was enough to maintain the storm’s structure and steer it along at about 20 mph (30 km/h). Rather than parking over one spot, the storm laid down a continuous ribbon of hail as it moved across Meridian. The high freezing level would normally melt small hail before it reached the ground but the sheer volume of stones and the rain-cooled core of the storm protected the mix on the way down.
A retention basin in Meridian, Idaho filled with floodwater and ice the morning after the severe thunderstorm. (Andruw Sorensen)Hail like this can enhance flooding by backing up storm drains and numerous videos from around Meridian last night showed just that. Meridian’s event was moving forward but when a thunderstorm producing significant amounts of small hail and rain like this parks over an area for a long time, flash flooding can be especially severe.
We don’t have exact data for the thunderstorms that caused the 1903 Heppner flood in Oregon but I think it’s reasonable to assume that that’s what happened in the Blue Mountains upstream of town. The flood that struck Heppner on June 14, 1903 remains the deadliest natural disaster in Oregon history and the second deadliest flash flood in the United States. While these kinds of storms bring significant novelty factor, they should not be taken lightly.
Another notable hail flooding event is recorded in the book *Isaac’s Storm* by Erik Larson. He writes that while the book’s subject, Isaac Cline, was in San Angelo, Texas he observed “an escarpment of water” that was 15-20 feet (4.5-6 meters) high descending the Concho River, taking out a group of three people who had been crossing at the time.
The source of this flood was a mystery until over week later when visitors came into town from upstream and described “a monstrous hailstorm” that “discharged stones the size of ostrich eggs.” In this case, the hail was not a blanket of tiny stones like what was observed in Meridian on Friday evening but it carries the same point – that prolific hail events can lead to destructive flash flooding.
Beyond flooding, huge amounts of small hail like this can also cause crop damage. Several commenters on the [Ingalls Weather Facebook page](https://www.facebook.com/ingallswx ) reported damage to plants in backyard gardens despite the small diameter of the stones. Hail that arrives in overwhelming numbers tears at everything it lands on. Immediate consequences include broken stems, ripped off leaves, and beaten or fallen fruit.
Shredded leaves make the plant less able to photosynthesize and these wounds open the door to fungus and insects. Thus, damage and disease can spread after the storm has passed. The toll is dependent on timing as leaf damage is most severe in the spring when plants are tender. A blanket of small hail also lingers, chilling the ground and the base of the plants for hours after the sky clears. Photos show piles of hail remaining around Meridian the morning after the event.
Other recent examples of small hail creating a snow-like blanket on the ground include storms in Marathon, Texas in 2024 and Vicksburg, Michigan in 2019. The high altitude of Colorado’s Front Range cities (Denver, Colorado Springs, etc.) makes them slightly more susceptible to events like this but it still remains a rare phenomenon there.
*The featured image was taken during the hail storm in Meridian, Idaho on June 26, 2026. (Tanya Sorensen)*
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