This afternoon, the weather setup is a little complicated as two areas of energy move northeast across the region. One is already north of Sioux Falls, while a stronger one is moving through the Nebraska Panhandle. Clouds across much of the area may limit how unstable the atmosphere becomes. A front stretches from central Nebraska through areas north of Omaha and Ames, and while it may drift slightly north this evening, most locations north of the boundary are expected to remain storm-free through late afternoon.
By late afternoon and evening, the atmosphere will become increasingly unstable, especially along and south of Interstate 90. New thunderstorms are expected to develop after 5 p.m. in parts of northeast Nebraska and south-central South Dakota. Any storms that form first could quickly become severe, producing hail up to 2 inches in diameter and wind gusts of 70 mph. Additional storms may develop farther south and move north toward the Missouri River during the evening.
As the night goes on, there is a small chance for a brief tornado, mainly south of I-90, if storms remain isolated. However, the tornado threat remains low. Storms are expected to gradually merge into larger clusters as they move east-northeast into Minnesota and Iowa, increasing the risk of damaging winds over 70 mph. A brief spin-up tornado cannot be ruled out in northwest Iowa, but the chance is very low. Most storms should move east of the area by around 2 a.m. Afterward, light winds and damp ground could allow patchy fog to develop overnight…