BOZEMAN - Strong to damaging wind gusts associated with thunderstorm development impacted SW Montana Friday night. Numerous reports of wind gusts between 50 and 60 mph from Dillon to Butte.
A Pacific storm is digging into western Montana with an upper-level Low building over NW Montana. This is producing wrap around bands of thunderstorms Friday evening over SW Montana. Powerful wind gusts remains the greatest concern. The reason for the powerful gusts is due to evaporational cooling. As moisture falls from building thunderstorms and passes through the very dry surface air the moisture will evaporate. This causes rapid cooling. Cool air is dense, meaning it's heavier and sinks abruptly down to the surface causing powerful and damaging wind gusts.
This line of storms started around the MT/ID state line near Dillon around 6 pm and lifted to the NE impacting Dillon with peak wind gusts of 63 mph at 6:26 pm Friday night. This also prompted the National Weather Service to issue a Severe Thunderstorm Warning (now expired).
That line of thunderstorms made it to Butte a little after 7 pm and continue to lift toward Helena.
Peak wind gusts as of 8 pm Friday night:
Dillon 63 mph
Wise River 57 mph
Newcomb 54 mph
Butte 49 mph
Bannack 48 mph
Anaconda 43 mph
Sheridan 40 mph
These storms did postpone many area High School football games Friday night with lightning and strong wind gusts to blame for the delays.
The video above is from the Butte EyeCam and the video is 5 minutes sped up 20x. There are visible electrical flashes on the flats in Butte as the gusts impacted the south-side of Butte before rolling up into Walkerville.