EF2 tornado in Massac County, Illinois

The tornado gained strength after crossing into Massac County from Pulaski County. North of the Mermet Lake Conservation Area, the tornado reached peak intensity. A barn was destroyed, and debris was thrown several hundred yards. Two grain bins were destroyed, including one that was thrown over 265 yards. Other small outbuildings were destroyed. There was minor to moderate damage to four homes from falling trees and strong winds. As the tornado moved northeast, it damaged a house near the Massac/Johnson County line. The back porch was ripped off. Trees were snapped and thrown into a vehicle and garage. There was roof, siding, soffit, and shutter damage to the home as well. In a nearby field, an irrigation system was overturned. The tornado funnel was photographed from a residence near Round Knob. Peak winds were estimated near 115 mph. The average path width was 300 yards. The tornado continued northeast into Johnson County.

Numerous strong to severe thunderstorms occurred in the warm sector of a low pressure system over central Missouri. The air mass in the warm sector was very unstable, with afternoon mixed-layer cape values in the 2500 to 4000 j/kg range. A 65 to 75 knot mid level jet was located across Arkansas, with the nose of the jet moving into western Kentucky. This feature enhanced the lift and strong deep-layer shear already in place, creating an environment very favorable for supercells and tornadoes. A 40 to 55 knot low level jet across eastern Arkansas moved into western Kentucky during the evening, resulting in isolated tornadoes and widespread damaging winds.