EF0 tornado in Wabash County, Illinois

An EF-1 tornado (peak of EF-0 in Wabash County), which began in far northeastern White County south of Grayville, crossed into Wabash County from the Kingdom Island portion of Gibson County. The tornado produced minor tree damage before crossing the Wabash River into Gibson County, IN. Peak estimated winds with this short Wabash County segment were 75 mph.

The second major severe weather outbreak for the month occurred on the 26th for the Quad State region. On the synoptic scale, a shortwave trough centered in the middle of the country with a 60 kt mid-level jet moved across northern Arkansas. A weak surface low was moving into SE Missouri during the morning with a secondary low located further northwest. A warm frontal boundary was draped across our area. A bowing line progressed east across SE Missouri into W Kentucky and far S Illinois between 0500-1000CST, followed by a mostly sub-severe second line that exited the region by 1300CST. The environment recovered producing fuel for more severe storms, starting with supercells 1800-2100CST with a line of storms moving east-southeastward across the entire Quad State after 1900CST, crossing through by midnight. Across the Quad State, this event produced the record for most tornado track miles in a single day in office history, along with the second most warnings issued in a day (just behind the May 8, 2024 event). Widespread straight-line wind and tornado damage resulted in over 100,000 customers without power across the Quad State.

For the morning, MLCAPE values at 0700CST were 1000-1500 J/kg in S Illinois. Effective bulk shear was 40-50 kts with STP of 1. Precipitable water was 1.5-1.75 in. The morning storms mostly missed just south of S Illinois with some street flooding in Johnston City.

Heading into the evening, MLCAPE values at 1800CST were 2000-3500 J/kg in S Illinois. For S Illinois, effective bulk shear rose to 50 kts, with SRH around 150-250 m2/s2 and STP of 2-3.5. 0-1 km shear was 20 kts. Mid-level lapse rates were 7-7.5 C/km. DCAPE of 1200-1400 J/kg provided ample opportunity for downburst winds.

Three tornadoes occurred in S Illinois. Two of these were with the late afternoon to early evening supercells. An EF-3 in the Lake of Egypt area of Johnson County debarked some trees, damaged several homes in the Eagle Point Bay subdivision, and injured one person. An EF-1 tornado in Johnson and Union Counties ahead of the approaching cold front tracked southeastward to Buncombe. The third tornado, an EF-1, was with the cold front in the Grayville area, tracking into Gibson County, IN. The supercells produced several hail reports, with a 2 inch hail report near the Williamson/Saline County border. Training heavy rain produced significant flash flooding for the second time in a month in Saline County, focused on Harrisburg with U.S. 45 flooded and at least one water rescue. Rainfall amounts in Southern Illinois were 1-4 inches, with the highest amounts in Alexander/Pulaski County and along a line from Williamson to Gallatin County. Numerous trees and power lines were damaged with the supercells and the frontal passage. Late evening power outages amounted to roughly a third of Williamson, Union, Johnson, and Alexander Counties.