Thunderstorm Wind in Butler County, Iowa

Several tree branches down blocking roads in town. Time estimated by radar.

A derecho moved across northern Iowa, resulting in a swath of wind damage with gusts of 60 to 80 mph reported, along with two tornadoes that occurred along the leading edge of the line of storms. The line of storms developed with an embedded shortwave that rode over a larger upper level ridge. That ridge allowed for hot and humid conditions across the area with temperatures in the upper 80s to low 90s and dewpoints in the 70s, resulting in heat indicies well over 100. This made for a deeply unstable airmass with over 5000 J/kg of MLCAPE and the line of storms rode the CAPE gradient across northern Iowa overnight. With 30-35 kts of 0-6 km shear, convection was able to maintain strength, and 0-3 km shear near 25 kts orthognal to the line was able to provide just enough of a tornadic set up. The line of storms reach western portions of the area by around 11 pm local time and finally exited east just after 2 am local time. Widespread tree damage and power outages were reported with this line of storms.