High Wind in Helena Valley, Montana

ASOS station KHLN measured many gusts of 58 mph or greater over a half an hour, including a peak gust of 67 mph.

A robust trough digging southeastward from the Pacific Northwest brought a belt of strong mid and low-level westerly flow across the majority of the region December 18. Given the favorable timing of the strongest flow and cold front, winds were easily able to mix to the surface. A respectable pressure gradient also developed across the area, which helped a few sites reach high sustained winds. In northeastern areas the wind took longer to develop, eventually needing the surface low to pull away from AB toward SK. This propelled a front through the area that brought both strong winds as well as rain that fell onto very cold surfaces, resulting in slick roads.