Mesoscale Discussion 1489 NWS Storm Prediction Center Norman OK 0540 PM CDT Wed Aug 11 2021 Areas affected...Eastern IA...Southern WI...Northwest IL Concerning...Tornado Watch 424... Valid 112240Z - 120015Z The severe weather threat for Tornado Watch 424 continues. SUMMARY...Ongoing storms from eastern IA into southwest WI will continue to pose a short-term severe threat. The eastward extent of the threat this evening remains uncertain due to the impact of earlier convection across southern WI/northern IL. Storm coverage is being monitored for possible watch issuance across eastern IA. DISCUSSION...At 2230Z, a few intense cells are ongoing from eastern IA into southwest WI, within an environment characterized by large CAPE and effective shear of 25-35 kt. The mature storms in this region will continue to pose a short-term threat of locally damaging wind, hail, and perhaps a tornado or two into the early evening as they move eastward. Downstream into south-central WI/northern IL, the impact of morning convection is still evident, with relatively strong MLCINH persisting per recent mesoanalyses and low-level stratus increasing in recent visible imagery. Ongoing storms may tend to struggle with time as they move eastward, especially given the relatively limited large-scale ascent as the primary vorticity maxima move northeastward away from the area. Low-level warm advection may promote an increase in storm coverage later this evening, though this scenario remains somewhat uncertain. Meanwhile, across eastern IA, storm coverage remains uncertain into this evening, though with a conditionally favorable environment in place, watch issuance remains possible to the southwest of WW 424 if additional intense thunderstorm development appears imminent.