Big hail at night brought by a series of storms rolling over Colorado’s high plains northeast of Denver this week is raising questions among atmospheric scientists.
“It’s just not common to get baseball or larger hail after 10 p.m. — even in the ‘hail alley’ of eastern Colorado,” state climatologist Russ Schumacher said Thursday.
A flurry of hailstorms overnight ranked among the heaviest in state history, hitting mostly after 11 p.m. Wednesday, leading to 11 reports of baseball size hail (at least 3 inches in diameter) and 4 reports of hail exceeding 4 inches in diameter, Schumacher said in an email from his base at Colorado State University in Fort Collins. He plotted the reports on a graph and posted it on Twitter.
Previously, National Weather Service records show no more than 4 reports of hail that large on a single day, he said.
One line of the storms blew into northeastern Colorado from Nebraska, after producing a tornado. Another line developed just north of Denver and spread eastward into Morgan, Logan, Washington, Phillips, and Yuma counties.
Hail fell in the northeastern part of Colorado through 2 a.m. Thursday.
Big hail hits often on Colorado’s eastern plains, and multiple storms in June have dropped heavy rain and hail. “But the fact that this was dropping such large hailstones over a large area so late at night was really unusual,” Schumacher said.
Research into how a warming climate may be affecting the timing of storms has been limited, Schumacher said. A warmer atmosphere can hold more water, and that could be a factor driving unfamiliar weather events.
This week in Colorado, the late hail pelted houses as close to metro Denver as Fort Lupton. And out on the plains around Brush, the storms led to the widespread breaking of windows, weather service meteorologist David Barjenbruch said.
Hail so big so late at night in Colorado is “extremely rare,” Barjenbruch said. “Typically in Colorado, we get rounds of afternoon rain and thunderstorms, and then things settle down overnight.. ….. This year, we have had a continuing unstable environment. There’s been a lot of low-level moisture. And low-level moisture, combined with daytime heating, are the two key ingredients to producing very large thunderstorms with hail.”
