http://blog.starvalleyweather.com/2020/08/05/teton-village-balloon-accident-on-august-3-2020-caused-by-micro-burst/

A serious incident involving the Hot Air Balloons launched near
Teton Village occurred around 8 am Monday morning August 3 2020. From all
indications a micro burst accompanying high based convection was the primary
mechanism for the sudden winds that impacted the balloons. While micro bursts
are not uncommon during the summer given environmentally favorable conditions,
typically they occur after the ground has heated sufficiently to steepen the
lapse rates and enhance the convective potential during the afternoon. A concern
for the occurrence of micro bursts at 8 am is unusual. The following discussion
and images will give some insight about this particular event.