Hail in Benewah County, Idaho

A severe thunderstorm developed northwest of the St. Joe National Forest. The thunderstorm intensified as it moved northeast between Heyburn State Park and St. Maries. The thunderstorm proceeded to head northward as a new updraft developed across Benewah County into Kootenai County.

A deep upper level trough of lower pressure was situated just off the west coast of the United States in the eastern Pacific. Good dynamics at the base of this trough and a southerly, divergent flow pattern at upper levels generated a baroclinic zone that stretched across the Idaho Panhandle. Low level moisture streaming northward east of this zone resulted in an unstable atmosphere across the warm sector that included the Idaho Panhandle. A strong veering shear profile in this same area provided the ideal ingredients for supercell development.