On the afternoon of May 28th, strong thunderstorms developed over southeast Washington and the southern Idaho Panhandle region. These storms moved very slowly to the northwest, which is a somewhat unusual direction for storm motion. One storm in particular though moved very little, anchoring itself over the hilly terrain northeast of Moscow, ID. The radar loop below shows the thunderstorm activity. Note the persistent strong storms between Potlatch and Deary.
The persistent storm produced a very impressive hailstorm. This storm occurred along Highway 9 between Deary and Princeton.
The images below show the Idaho Highway Department clearing the highway of the hail. Some of the hailstones were as large quarters and accumulated to a depth of up to 4 inches.
www.weather.gov 
