Mesoscale Discussion 1381 NWS Storm Prediction Center Norman OK 1043 PM CDT Sat Jun 22 2024 Areas affected...parts of west central through northern Illinois...southwestern lower Michigan...northwestern Indiana Concerning...Severe Thunderstorm Watch 447... Valid 230343Z - 230545Z The severe weather threat for Severe Thunderstorm Watch 447 continues. SUMMARY...An evolving line of storms may pose some further increase in potential for strong to severe surface gusts for another hour or two. But this appears likely to diminish after around 1 or 2 AM CDT, as storms weaken while continuing east-southeastward through the southern Great Lakes/Ohio Valley vicinity. A new severe weather watch is not anticipated, but trends will continue to be monitored. DISCUSSION...Convection has been gradually consolidating into a line generally coincident with strengthening low-level frontogenetic forcing. This trails a developing surface cyclone now migrating across Lake Michigan into lower Michigan, and will continue to slowly advance east-southeastward across the southern Lake Michigan and northern Illinois vicinity into the overnight hours. Although subtle low-level moisture return is still possible immediately ahead the evolving line, beneath a 30-40 kt west-southwesterly jet around 850 mb, the downstream boundary-layer, in general, is somewhat drier and characterized by increasingly weak potential instability beneath relatively warm mid-level air. So, it appears that ongoing convection could maintain intensity, or perhaps intensify a bit further, with sub-cloud evaporative cooling contributing to downward mixing of momentum and a few strong to severe surface gusts during the next couple of hours. However, beyond 06-07Z, this seems likely to diminish as convection begins to weaken. ..Kerr.. 06/23/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IWX...GRR...LOT...ILX...LSX...DVN... LAT...LON 41419007 41668932 41848824 42018665 42558619 42358539 41258707 40818876 40019060 40789076 41129045 41419007