A large cluster of thunderstorms continues this morning from western Illinois into Missouri and far eastern Kansas, fueled by strong warm and moist air advection associated with a powerful southwesterly low-level jet. As we move through the day, the atmosphere downstream of these ongoing storms will gradually recover and destabilize. Some of the ongoing storm clusters may re-intensify later today, especially as low-level lapse rates steepen during the afternoon. Damaging winds would be the primary concern with these storms as they move across central and southern Illinois and eventually into Indiana. The severe threat should gradually weaken farther east into the Ohio Valley this evening where instability and wind shear become less favorable.
Farther west, attention increasingly turns to Kansas and southeast Nebraska, where the outflow boundary left behind by this morning’s storms will likely play a major role in where the highest severe weather threat develops later today. There is some concern that ongoing convection and the southward drift of this boundary could delay destabilization during the afternoon. Even so, strengthening winds aloft and increasing large-scale lift ahead of an approaching upper-level disturbance should overspread the warm sector by mid to late afternoon.
Despite lingering uncertainty regarding cloud cover and boundary placement, the atmosphere south of the front and east of the dryline is expected to become extremely unstable by late afternoon. Very steep lapse rates aloft combined with a warm, moist boundary layer will support explosive thunderstorm development across central and northeast Kansas into far southeast Nebraska. Initial storms are expected to be discrete supercells capable of producing very large to potentially giant hail in the 2 to 4 inch diameter range.
As we move into the late afternoon and evening, strengthening low-level winds will increase tornado potential across central and northeast Kansas into southeast Nebraska and northwest Missouri. This environment may support a focused corridor of strong to intense tornadoes with any sustained supercells that remain isolated.
Storms are then expected to grow upscale fairly quickly during the evening as interactions between storms increase and the cold front pushes eastward. Even as storms merge into a larger line or cluster, the tornado threat is expected to continue with embedded circulations and line-embedded supercells. Damaging winds will also become an increasing concern through the evening and overnight hours as the storm complex spreads east across Kansas, Missouri, and Oklahoma. Some severe wind threat may persist well into the night given the strongly unstable air mass expected to remain in place ahead of the storms.