The flow aloft is strong, and the easterly flow will raise dew points under the scenario in which the severe storms take shape. Impulses, or bursts of energy are also expected off the mountains.

"It creates a lot of good spin and sustains a lot of updrafts," NWS meteorologist Brian Tesar said Wednesday morning. Those strong updrafts keep hail aloft longer, increasing its size before it falls to the ground.

"Historically, the parameters we're looking at today have produced up to baseball, softball-sized hail in parts of Montana," Tesar said.

By Wednesday evening in Billings the storms seemed to have passed and weren't particularly severe. Billings saw light thunder, but no hail within the city. That seems to show a bit of a trend for Billings, which has avoided the big storms so far this season.

"If we get some rain during the morning and early afternoon that stabilizes the air mass in the area. If it's stable you can't get severe weather," Arthur said.

Arthur theorized that has been happening frequently in Billings because the spring and beginning of summer have been particularly moist.