Thunderstorm Wind in Williamson County, Illinois

A surging portion of a storm line caused damage along Cedar Grove Rd north of Marion. Multiple trees were snapped or uprooted. Shingle damage occurred to homes and buildings. A play set was torn up and parts of fences downed.

Multiple rounds of severe thunderstorms impacted the Quad State region on the 27th. The later rounds of storms began with isolated to scattered storms tracking northeastward late afternoon into the early evening. On the synoptic scale, an upper level jet ejected across the Missouri Valley during the evening with a pronounced mid level wave moving through. The low level jet strengthened into the evening. A surface low was positioned near St Louis during the early evening with a trailing cold front extending southwestward. A broken band of supercells developed along this and eventually congealed into more linear segments as it moved into Southern Illinois compared to its more discrete structure in Southeast Missouri.

In Southern Illinois, during the early evening, MLCAPE was quite high ahead of the frontal boundary with values of 2000-3000J/kg, along with deep layer shear of 50-60kts, STP of 4-7, and mid-level lapse rates of 8C. A moderate risk for severe weather covered most of Southern Illinois for the evening hours.

A few late afternoon cells tracking northeastward produced hail in Edwards/Wabash Counties. For the storms arriving from the west during the evening, wind damage became the primary hazard for Southern Illinois. The highest concentration of damage south of Herrin and north of Marion in Williamson County, with damage to multiple homes in both locations.