One hail of a storm pounded northcentral Montana Friday

Karl Puckett
Great Falls Tribune
PA Lee took this photograph of a supercell Thunderstorm on Moroney Dam Road outside of Great falls at 3:20 p.m. Friday.

It began at about noon near Babb.

It broke up over the Highwood Mountains. 

Over its 193-mile, southeasterly journey across northcentral Montana it produced dark and otherworldly-looking skies and left a trail of hail, some the size of tennis balls, and damaged vehicles and homes.

Hail covers a field Friday afternoon near the Chouteau-Cascade county line.

Four hours later, the supercell thunderstorm finally petered out, and Montanans had something to talk about for the rest of the weekend.

"The thing that was interesting about this storm was its longevity," said Paul Nutter, a meteorologist with the National Weather Service in Great Falls. "It's a little unusual for a storm to hold together for that long of a track in our forecast area."

The long-lived supercell, or rotating thunderstorm, clipped along at a medium pace of about 30 mph to 40 mph, cutting a path clear across northcentral Montana, after beginning near Babb in Glacier County adjacent to Glacier National Park.

From there it moved southeasterly and through Valier, Conrad and Dutton.

"Those three areas were all hit pretty hard with hail — large hail," Nutter said.

Large Hail near Cascade and Chouteau County Line.

The largest hail — 2.5 inches in diameter, about the size of a tennis ball — was reported east of Dutton.

"We don't see that very often but it's not unprecedented," Nutter said. 

Golf ball-sized hail was reported in Valier, where it damaged siding and vehicles and shattered windows.

Along with hail, the supercell thunderstorm produced high winds, from 41 mph to 54 mph.

A supercell thunderstorm rolls past Great Falls to the north Friday afternoon.

As the storm moved into Cascade County it began turning more to the southeast and just missed Great Falls but its big black mass was clearly visible from the city.

Nutter said it finally broke up over the Highwood Mountains.

"It was a really interesting storm," Nutter said. 

Strong storms developed in advance of the supercell storm around Geraldine and the Square Butte area.

That used up some of the supercell's energy, Nutter said.

"That may have contributed to its demise," he said.

Biggest hail 

2.5 inches: Eight miles east of Dutton

2: Fives miles east of Dutton

1.75: Valier and five miles south southeast of Valier.

1.5: Five miles south south east of Conrad, three miles east northeast of Dutton and 6 miles west southwest of Floweree.

1.25: 13 miles east southeast of Browning, 5 miles north of Dutton.

Highest winds

Eight miles north of Brady: 54 mph

Julie: 51 mph

Judith Peak: 49 mph

Great Falls: 44 mph

Most rain

Geraldine: 0.75