Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Sat Sep 14 2019 Valid 142000Z - 151200Z ...Upper Midwest to the central Great Plains... Elevated thunderstorms are ongoing in western IA on the leading edge of a low-level warm theta-e advection plume. This plume and attendant zone of ascent will spread east-northeast across the Upper MS Valley into tonight in advance of a low-amplitude shortwave trough near the ND/MB border that will move east-southeast into Lake Superior. This elevated convection will pose a threat for isolated large hail, mainly this evening into tonight with a probable decay cycle this afternoon. A risk for locally damaging winds may also develop tonight towards the IA/IL/WI border region if a cluster can become semi-organized. In the wake of the warm advection regime, storm initiation will depend on weak low-level ascent along a surface trough that extends southwestward across NE/KS. Stronger surface heating and deeper mixing is expected along the trough in KS, with lesser mixing depths and a greater probability of maintaining MLCIN through the afternoon in the warm sector farther northeast. Thus, surface-based thunderstorm development should be sparse and may struggle to be sustained during the late afternoon/early evening. If surface-based storms can form as far northeast as southern MN this afternoon, vertical shear profiles will be sufficient for supercells. Weaker vertical shear is expected with southwestward extent into southwest KS, where high-based storms would pose a threat for isolated severe wind and hail.
