Mesoscale Discussion 1442 NWS Storm Prediction Center Norman OK 1140 AM CDT Sun Aug 08 2021 Areas affected...Portions of central/eastern MO and western/southern IL Concerning...Severe potential...Watch possible Valid 081640Z - 081915Z Probability of Watch Issuance...60 percent SUMMARY...A threat for scattered damaging winds and severe hail should increase this afternoon. Watch issuance is possible. DISCUSSION...Widespread cloudiness is present across much of western MO this morning, which has limited heating across this area so far. Less cloud cover over central/eastern MO into IL has allowed surface temperatures to generally warm into the 80s as of 1630Z. A very moist low-level airmass depicted on the 12Z SGF sounding and evidenced by low to mid 70s surface dewpoints from various observations sites is present across this region. Continued diurnal heating will likely allow 2000-3000 J/kg of MLCAPE to develop by peak afternoon heating. A shortwave trough evident in water vapor satellite imagery will move eastward from the central Plains towards the mid MS Valley through the rest of the day. Large-scale ascent preceding this feature will likely encourage the development of scattered to numerous thunderstorms this afternoon across much of central/eastern MO and eventually into western IL. Initial storms will probably focus along a differential heating zone and remnant outflow boundary present across south-central MO as small-scale perturbations embedded within the shortwave trough overspread this area. Mid-level flow is not expected to be overly strong, but marginal deep layer shear around 25-30 kt should be enough to support some storm organization. Convection will probably tend to form into multiple clusters with time. As low-level lapse rates continue to steepen, damaging downdraft wind gusts should become the primary threat. But, isolated severe hail may also occur with initially more discrete development. Trends will be monitored for signs of increasing convective coverage and intensity, with watch issuance possible early this afternoon.