Stormclouds roll into Bozeman

Reader Megan Biggs sent in this photo of the Sept. 30, 2013, shelf cloud rolling into Bozeman.

Unless you were in a windowless room, it was nearly impossible to miss the low, ominous, gray cloud gliding slowly over Bozeman Monday morning.

Known as a shelf cloud, the formation is not unusual, National Weather Service meteorologist Nick Langlieb said. However, it is unusual for a shelf cloud to float so low to the ground.

“It looked more ominous because it wasn't a couple thousand feet in the air,” he added.

Shelf clouds form when relatively cool air associated with a line of showers meets warmer air, causing condensation and creating a cloud.

Monday's cloud formation was part of a storm system that included lightning in the Bridger Mountains and “a few rumbles of thunder along the (cold) front,” Langlieb said.

In about an hour, the storm system dropped roughly a third of an inch of rain. It brought with it wind gusts up to 35 mph in Belgrade, where the weather service has an automated monitoring system.

That brought the month's rainfall amount to 2.13 inches — making this the wettest September since 1983, when 3.17 inches of precipitation fell, Langlieb said. The wettest September on record was in 1947, when 4.5 inches of precipitation dropped.

Before factoring in this year's data, average rainfall for September is just a little more than 1 inch.

“It's definitely above average,” Langlieb said. “That's good, we definitely need the precipitation.”

The weather service's drought monitor indicated most of Gallatin County is still experiencing moderate drought, but it was last updated about a week ago. Madison County and the western part of Gallatin County were still listed as having extreme drought conditions.

Bruce Wright, vice president of the Montana Farm Bureau, said the rain was welcome, even if it came too late to help this year's crops.

“It won't do very much for this year, but it's really great for next year because a lot of people are seeding winter wheat,” he said.

Though wet conditions can be harmful to unharvested grain, the moisture will help recharge the area's groundwater.

“I think most people are done (harvesting),” Wright said. “And I think people are happy to see this moisture.”

Jodi Hausen can be reached at jhausen@dailychronicle.com or 582-2630. Follow her on Twitter @JodiHausen or on Facebook at Jodi Hausen, journalist.