EF3 tornado in Franklin County, Illinois

This large tornado entered Franklin County from Jackson County. The tornado originally formed near Perryville, Missouri. The most intense damage in Franklin County was located south of Mulkeytown, where the tornado was rated EF-3 based on a house that was swept clean off its foundation. Debris was thrown up to a mile downwind. The debris was shredded, with nothing larger than 2-by-4 wood pieces. However, the house was sitting on a block foundation, unattached to anything. Based on the lack of any anchors for the house, peak winds were estimated near 160 mph at this site. Most of the other damage in this rural area of Franklin County consisted of snapped trees, heavily damaged barns, and a few damaged houses. The tornado rapidly weakened from EF-3 intensity to complete dissipation during the final two miles of its path. The average path width in Franklin County was 340 yards. The total path length starting near Perryville, Missouri was nearly 50 miles. The tornado dissipated just southwest of Christopher.

Isolated supercell thunderstorms moved into southern Illinois during the evening hours. The storms developed ahead of a cold front in a destabilizing air mass characterized by dew points in the lower to mid 60's. The most intense supercell storm awaited the approach of a mid-level impulse from Oklahoma, which was downstream from the primary shortwave trough over the southern Plains. The supercell produced two long-track strong tornadoes, the first of which originated in Perry County, Missouri and tracked almost 50 miles before dissipating. The second strong tornado formed in the Wabash Valley and crossed into southwest Indiana. A southwesterly low-level jet increased substantially during the evening, creating favorable conditions for tornadoes.