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

SPC AC 110551 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1151 PM CST Tue Nov 10 2026 Valid 111200Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OHIO AND WESTERN TENNESSEE VALLEYS... ...SUMMARY... Thunderstorms capable of isolated large hail, damaging wind gusts, and perhaps a tornado will be possible Wednesday afternoon and evening across parts of the Ohio and western Tennessee Valleys. ...Synopsis... A lead short-wave trough will move through portions of the southern Great Lakes and OH Valley on Wednesday, ahead of a stronger upstream system and attending mid/upper-level wind maxima, which will progress through the mid-MO and mid-MS Valleys into the Mid-South/TN Valley. The net result will be a broad zone of height falls/forcing for ascent overspreading the OH and TN Valleys Wednesday afternoon into night. In the low levels, a cyclone will track from eastern IA at 12Z Wednesday through central IL and IN during the afternoon before reaching the upper OH Valley late Wednesday night. Meanwhile, a trailing cold front will advance southeast through the mid-MS, much of the OH, and TN Valleys during the forecast period. ...Ohio Valley into the Mid-South and Tennessee Valley... 00Z observed soundings and current surface observations indicate the presence of a partially modified continental-polar air mass in place over the southern Plains into Ozark Plateau, characterized by boundary-layer dewpoints in the 50s and lowest 100-mb mean-mixing ratios of 9-10.5 g/kg. That moisture will be advected into the region on Wednesday ahead of the front and beneath a plume of modestly steep mid-level lapse rates (e.g., 7-7.5 C/km), yielding a relatively narrow axis of MLCAPE of 750-1250 J/kg by mid-late afternoon. Divergence aloft in the exit region of the upper-level jet streak will enhance convergence in the vicinity of the surface low and trailing front, resulting in a gradual increase in storm coverage and intensity through the afternoon, initially from northern and eastern IL into IN. Subsequent storm development is anticipated by late afternoon into evening from portions of western and central KY into middle TN, though storm coverage is likely to decrease with southward extent. The presence of 35-40 kt of effective bulk shear with a vector orientation largely perpendicular to the surface front should favor semi-discrete storm modes, which is consistent with several REFS ensemble members. The somewhat marginal CAPE-shear parameter space may limit the potential for sustained supercells, and an associated greater severe weather threat. Nonetheless, the relatively steep low/midlevel lapse rates with 500-mb temperatures approaching -20 C will be supportive of isolated occurrences of large hail and damaging winds, especially with any transient supercell structures and/or bowing line segment. A tornado is possible during the late afternoon or early evening as low-level shear strengthens. However, convective inhibition is expected to increase fairly quickly during the evening, suggesting any threat will be short-lived. ...Central and Southern Florida... A moist and moderately unstable air mass (e.g., MLCAPE of 1000-1500 J/kg) is forecast to the south of a weak west-to-east oriented surface boundary/confluence zone over the central peninsula. Aided by the glancing influence of a weak disturbance passing to the north, thunderstorms should increase in areal coverage through the afternoon, especially from the south-central peninsula toward the Atlantic Coast. The presence of 35-40 kt of deep-layer shear may foster a few stronger storms capable of hail and/or outflow winds approaching severe levels. ..Mead.. 11/11/2026 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z