Hail in Pondera County, Montana

Measured by a trained spotter 5 miles SE of Valier.

The Storm Prediction Center includes a portion of the CWA in a marginal risk area for severe Thunderstorms. A mid-level shortwave trough dives southeastward from British Columbia and Alberta. This trough works with a relatively moisture rich environment producing showers and thunderstorms by early afternoon. This area roughly extends north and east of a Cut Bank to Lewistown line. A few long-lived severe thunderstorms form in an environment containing moderate instability and favorable shear. The storms track east southeastward along and just behind an advancing surface front. Strong storms form along this frontal boundary where daytime heating provides elevated CAPE. With outflow dominance, storms merge into more of a storm cluster as they move eastward.