A microburst was blamed for a tent collapse in Blount County Thursday night that injured a dozen people. Three of the injuries were described as serious. The National Weather Service estimated a thunderstorm in the area generated winds of 40 miles per hour. A microburst occurs when there is a downdraft during a thunderstorm. Witnesses said the storm seemed to come out of nowhere, and that the wind appeared to be circling around Hayden's Traditions Park. The tent was erected for a Traditions Bank shareholders party. The tent's curtains were rolled up during the event, likely enhancing the uplift of the structure, a NWS damage survey found.