Severe weather outlook: Marginal risk of severe thunderstorms across IL, IN, KY, OH

SPC AC 111255 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0655 AM CST Wed Nov 11 2026 Valid 111300Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN ILLINOIS INTO INDIANA...WESTERN/CENTRAL KENTUCKY...AND MIDDLE TENNESSEE... ...SUMMARY... Thunderstorms capable of producing isolated hail, damaging winds, and perhaps a tornado may occur this afternoon and evening across parts of eastern Illinois into Indiana, western/central Kentucky, and middle Tennessee. ...Midwest/Lower Ohio Valley into Middle Tennessee... Recent water vapor satellite imagery shows a mid-level shortwave trough digging southeastward over the Upper Midwest towards the mid MS Valley, with recent elevated thunderstorm development noted over eastern IA capable of producing small hail (reference ~300 J/kg MUCAPE in the 12Z observed DVN sounding). A related weak surface low will develop from southeast IA this morning to the IN vicinity by late afternoon/early evening. A trailing cold front will continue advancing east-southeastward across the southern Plains, mid MS Valley/Mid-South, and lower OH Valley this afternoon and evening. The main uncertainty and likely limiting factor to severe potential today remains shallow/limited low-level moisture ahead of the front across the Midwest/lower OH Valley, where latest surface observations show dewpoints generally in the 30s to mid 40s. Somewhat greater low-level moisture associated with a modified continental polar airmass is present across the southern Plains into the Ozarks/lower MS Valley. But, west-northwesterly low-level flow noted in area VWP trends and forecast low-level trajectories suggest this moisture will struggle to advect northward through the day, perhaps reaching parts of middle TN/southern KY. Therefore, most guidance appears a bit moist with boundary-layer dewpoints and related instability this afternoon, although some mid-level moistening could occur. Current expectations are for surface-based thunderstorms to initially develop over eastern IL by 18-21Z, with additional development possible with southward extent along/ahead of the front in western/central KY through the afternoon/early evening as the boundary layer gradually destabilizes. The combination of weak, but potentially sufficient, MLCAPE and 30-40 kt of deep-layer shear oriented largely orthogonal to the surface cold front should support updraft organization. A mix of clusters and marginal supercells are expected to evolve and spread quickly eastward while posing an isolated threat for hail and damaging winds given cold mid-level temperatures and modestly steepened low-level lapse rates. However, the lack of greater low-level moisture/stronger instability should tend to limit the overall severe threat. Modestly enhanced low-level shear may also support a tornado risk, especially if a supercell can develop and be sustained. But, tendency for low-level flow to veer to westerly should reduce effective SRH with time through the late afternoon/evening. The isolated severe risk should wane this evening with eastward extent across the lower OH Valley as instability diminishes with the loss of daytime heating. ...Central/Southern Florida Peninsula... Isolated to scattered thunderstorms should preferentially form along the Atlantic Coast sea breeze this afternoon across the central/southern FL Peninsula. Glancing large-scale ascent associated with a weak mid-level perturbation over the Southeast should aid this convective development, but multiple inversions aloft noted in the 12Z observed MFL/TBW soundings should tend to limit updraft intensities. Still, small hail and gusty winds could occur with the stronger cores given the presence of moderate instability and 30-35 kt of deep-layer shear. ..Gleason/Wendt.. 11/11/2026 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z