High Wind in Gates of the Mountains, Montana

Numerous sensors and a trained spotter reported gusts in excess of 58 mph or sustained winds averaging at least 40 mph over an hour or more, including mesonet station MTSBN Sieben Flats (MT DOT), RAWS station DBOM8 Dearborn and NW Energy sensor Birdseye Rd. The peak gust reported was from the trained spotter 7 miles east of Marysville, which was 80 mph. The trained spotter also reported a 40 foot tall pine tree was toppled due to the winds. Additionally, the Sieben Flats sensor measured sustained winds averaging 41 mph between 931AM and 234 PM, at which time the sensor lost power and stopped reporting. The last observation at this sensor before reporting stopped was sustained winds of 60 mph with a gust to 79 mph.

Robust low to mid level flow westerly flow associated with a potent shortwave and attendant cold fronts resulted in a prolonged period of high-end winds and gusts across the entire region Dec 17 into the 18th. Multiple gusts in excess of 90 mph were observed in populated areas, with a peak observed gust of 104 mph west of Bynum. Prolonged power outages were observed across the region, mostly due to trees being damaged/falling over completely. Additional societal impacts included extremely difficult to impossible travel conditions, which prompted a Civil Emergency Message for areas along the Rocky Mountain Front the afternoon of the 17th.