EF1 tornado in Nemaha County, Nebraska

A tornado developed just south of Highway 136 and west of 636 Avenue, and moved east northeast to the area near Highway 136 and just east of 637 Avenue. This tornado caused sporadic tree damage and uprooting, and impacted two farms. At one farm, a large trailer was rolled approximately 50 yards and debris distributed downstream across a field. Several trees were snapped or uprooted and landed on a home. Another farm had a large shed destroyed with the debris field extending more than a half mile downstream. Maximum wind speeds were estimated at 100 mph. This tornado was embedded in a broad area of straight line downburst winds estimated at up to 95 mph, especially near and just south of the tornado track.

On the afternoon of May 18, severe thunderstorms produced tornadoes, damaging winds gusts, hail and flash flooding across southeast Nebraska. a strong shortwave trough ejected eastward across the region, providing robust forcing for large-scale ascent. Despite lingering morning cloud cover, very steep mid-level lapse rates combined with the daytime heating of a moist low-level airmass to generate strong instability south of an advancing cold front. Mesoanalysis revealed strong theta-e advection extending from central Kansas through southeast Nebraska and southwest Iowa, highlighting the rapid return of a highly volatile environment. Thunderstorms initially initiated on the warm side of the boundary over northwest Kansas before additional development began over far southeast Nebraska by 2:00 PM CST. This convection initially exhibited discrete supercell characteristics before eventually transitioning into a broader multicell cluster. Additional cells developed north of the cold front across eastern Nebraska, bringing primarily an isolated hail threat.

The system dropped large hail up to golf ball size (1.75 inches) and generated destructive straight-line winds, including a measured peak gust of 90 mph. The initial supercell storm mode was particularly prolific for tornadogenesis, resulting in 8 tornado across southeast Nebraska. While several of these tornadoes were brief, others caused concentrated damage to trees, farm outbuildings, and irrigation pivots'most notably in Johnson, Nemaha, and Richardson counties. In several instances, these tornadoes were embedded within even broader swaths of intense 80 to 95 mph downburst winds. As the storms transitioned into a messy multicell cluster, torrential downpours also triggered isolated reports of flash flooding.