Flash Flood in Lemhi County, Idaho

A high precipitation, left-moving supercell caused very heavy rainfall to fall over the Mustang burn scarred Owl Creek drainage basin inducing a large debris flow. Doppler radar estimates of 0.58 fell 30 minutes ending at 7:28 pm MDT over this basin. The debris flow severely damaged landowners' property including water and fuel barrels, irrigation system and several out-buildings. The debris flow also deposited up to 3 feet of rock and mud plus trees over Salmon River Rd. A few hours later a spotter in North Fork measured 0.50 of rain in 20 minutes.

Earlier in the day a surge of monsoon moisture tracked into the region from Nevada allowing for a good buildup of atmospheric moisture. A 40 knot west-southwest, mid-level jet maximum associated with an upper level wave combined with above normal moisture content (precipitable water values near one inch) and strong heating initiated supercell thunderstorms in the early evening hours over western Lemhi County. One particular supercell brought very heavy rains in a short amount of time inducing debris flow over several of the Mustang burn scars. The Mustang fire occurred in the summer of 2012.