SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1237 AM CDT Tue Sep 07 2021 Valid 071200Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR LOWER MICHIGAN...NORTHEAST ILLINOIS...AND NORTHERN INDIANA... ...SUMMARY... Damaging winds, as well as isolated large hail and a tornado or two, will be possible mainly this afternoon into the evening from Lower Michigan into northeast Illinois and northern Indiana. ...Lower MI/northeast IL/northern IN... An amplifying midlevel trough over the Great Lakes will feature a deepening surface cyclone over Ontario. A trailing cold front will move southeastward across the Great Lakes during the period. A narrow corridor of low-level moistening is expected immediately in advance of the front. Elevated convection will likely be ongoing this morning over WI/northern MI and additional storms are forecast to develop by midday along the leading edge of the outflow and/or cold front. Increasing large-scale ascent will favor the development of an extensive squall line (high confidence) from northern Lower MI southwestward into the mid MS Valley. Damaging gusts will be the primary hazard with the squall line but a tornado is possible with more pronounced inflections/bows within the squall line. ...Northern OK and vicinity... Strong surface heating/mixing and convergence along the front will likely lead to scattered thunderstorms developing by late afternoon over northern OK. Model guidance shows 60s boundary layer dewpoints contributing to 2000-3000 J/kg MLCAPE, which should favor multicellular clusters given adequate effective shear for organized storms. Isolated severe gusts will be the primary risk but severe hail could accompany the more intense updrafts early in the convective life cycle. ...Southern NM/AZ... A weak mid-level vorticity max is forecast to move from northeast NM southwestward to the NM/TX/Mexico border region by early evening. Strong heating amidst 50s dewpoints will yield 1000 J/kg MLCAPE according to forecast soundings by late afternoon. Isolated to widely scattered thunderstorms are forecast to develop within a flow regime characterized by 30-40 kt 6 km AGL flow. Strong to severe outflow winds are possible with the stronger cores. ..Smith.. 09/07/2021 Read more LIVE: spc.noaa.gov
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