EF1 tornado in Gibson County, Indiana

An EF-1 tornado, which began south of Grayville, IL, crossed over the Wabash River through part of Gibson County and Wabash County, before re-entering Gibson County. The tornado tracked eastward through Fort Branch, Indiana. A roof was removed from a business near there and billboards were destroyed. Several fields suffered crop damage as well. Hundreds of trees were downed along this path. Some of the most significant damage along the path then occurred between Ft. Branch and Somerville near E Lake Charles Dr and S 175 E, where a garage was destroyed along with roof and siding damage to several homes. Several hardwood trees were snapped and twisted at trunk level. Additional significant damage occurred to several farm buildings on S 550 E with one collapsing. The tornado then ended as it crossed Somerville. Estimated peak winds for the Gibson County segment, and the tornado as a whole, were 110 mph. We greatly appreciate the assistance of Shawn Weber who provided both drone and ground survey assistance with this long track tornado.

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, just S/SW of SW Indiana, 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.

SW Indiana was spared from severe weather impacts during the daytime rounds of storms. Heading into the evening, the most unstable environment was further southwest in SE Missouri and far W Kentucky, but MLCAPE values at 1800CST were 1500-2500 J/kg in SW Indiana. For SW Indiana, effective bulk shear rose to 50 kts, with SRH around 150 m2/s2 and STP of 2. 0-1 km shear was 20-25 kts. Mid-level lapse rates were 7-7.5 C/km. DCAPE of 1000-1200 J/kg provided ample opportunity for downburst winds.

As the front swept through SW Indiana during the evening, several reports were made of straight-line wind damage, primarily in Gibson County. A long track EF-1 tornado also entered into Gibson County from the Grayville, IL area, then proceeded over 30 miles eastward damaging many trees, fields, and some homes and farm buildings, including on the north side of Fort Branch, before finally dissipating near Somerville.