Hail in Gem County, Idaho

For the third consecutive day, thunderstorms forming in the flow around a cut-off low pressure system, moved east to west across southwest Idaho. The hardest hit areas were in Gem and Boise Counties, both of which are just north of the Boise metropolitan area. At 1443 MST, a thunderstorm produced dime-size hail in Idaho City, 25 miles northeast of Boise. Fifty minutes later, this same storm produced dime-size hail in Horseshoe Bend, 20 miles north of Boise. As the storm moved into Gem County, surface observations and radar indicated that it had intensified. Just north of Sweet, 25 miles north of Boise, a Gem County Sheriff reported quarter-size hail accumulating to a depth of two to three inches. The thunderstorm also began producing heavy rains near Sweet. A spotter at Black Canyon Dam, 25 miles northwest of Boise, received an inch of rain in less than an hour. These rains produced a rock slide across State Highway 52 south of Sweet. The rock slide blocked off the highway until midday the following day.