Mesoscale Discussion 1832 NWS Storm Prediction Center Norman OK 1237 PM CDT Mon Oct 11 2021 Areas affected...portions of north-central IL...eastern WI and northwestern MI Concerning...Severe potential...Watch possible Valid 111737Z - 111930Z Probability of Watch Issuance...40 percent SUMMARY...Ongoing convection ahead of the upper low may pose a risk for damaging winds and perhaps a brief tornado through much of the afternoon. However, cloud cover and stratiform rain cast considerable uncertainty on the convective evolution. DISCUSSION...As of 12:15 CDT, a well-defined upper low was located near the Mississippi river along the border of MO and IL. To the east, remnant convection and precipitation were ongoing across much of central and northern IL. Despite dense cloud cover, low-level warm advection ahead of the upper low has warmed surface temperatures into the low to mid 70s as far north as the IL WI border. With low-level moisture in place (mid 60s F surface dewpoints) SPC mesoanalysis shows weak buoyancy (MLCAPE of 500-1000 J/kg) has developed. Continued low-level advection and the arrival of strong dynamic lift ahead of a jet streak around the base of the upper low may support some additional destabilization, though the magnitude remains uncertain. The strong ascent timed with the arrival of the upper jet will also support very strong shear profiles across much of the upper Midwest and Great Lakes. Regional model sounding and VWPs showing 0-6 km shear of 50-60 kts with backed low-level flow also supporting large low-level hodographs. Thus, supercells would be the expected storm mode with a risk for damaging winds, hail, and perhaps a tornado or two. Convective evolution of the ongoing cluster of storms across north-central IL remains highly uncertain given the lack of stronger buoyancy and continued development of showers and thunderstorms ahead of the best kinematic environment northeast of the upper low. While several weakly rotating embedded elements have been observed over the last hour in central IL, the lack of greater buoyancy may result in poor storm organization this afternoon. Strong low-level shear (0-1 srh 200-300 m2/s2) and forcing will more than likely support some severe risk, through the evolution maybe very gradual and limited spatially. Farther downstream across portions of northern lower MI, greater clearing will likely support better buoyancy through much of the afternoon. Somewhat removed from the better dynamics of the upper low, a few strong/severe storms, including a supercell, may develop with a risk mainly for damaging winds. Despite the better buoyancy, the stronger flow aloft and better shear are forecast to arrive later in the diurnal cycle poorly timed with destabilization. As such, confidence also remains low on severe weather potential. Trends are being monitored for a possible weather watch though overall uncertainty remains very high.