Heavy Snow in Lewis and Southern Nez Perce, Idaho

A total of 8.4 inches of snowfall was recorded from the evening hours of the 9th through 1900PST on the 10th, and another 5.1 inches was recorded from 1900PST on the 10th through 0415PST on the 11th.

A cold front passage during the evening hours on the 9th resulted in a favorable northwest flow pattern into the Camas Prairie. A deep upper level trough of low pressure pushing into the region at the time produced a cold pool that steepened mid-level lapse rates, which resulted in an increasingly unstable environment. This long duration event continued into the early morning hours of the 11th before drier Canadian air was able to penetrate itself far enough southward onto the Camas Prairie. By the time the snow ended, Winchester had recorded over a foot of new snowfall.