ACUS01 KWNS 171256 SWODY1 SPC AC 171254 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Mon Aug 17 2026 Valid 171300Z - 181200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN AND CENTRAL PLAINS...AND THE SOUTHERN APPALACHIANS INTO THE NORTH CAROLINA PIEDMONT... ...SUMMARY... Thunderstorms with severe wind gusts and hail will be possible this afternoon and evening across parts of the central and northern Plains. Damaging gusts will also be possible in parts of the southern Appalachians into the North Carolina Piedmont, Oklahoma and Arkansas. ...Northern/Central Plains... Modest height falls are expected across the northern Plains as troughing over central Canada deepens. As it does, an associated surface low will shift eastward and an attendant cold front will push southward/southeastward across eastern MT, ND, and northwest MN. The airmass preceding this front will be moist and strongly unstable, with dewpoints likely in the upper 60s and MLCAPE over 2500 J/kg. Several different areas of initial development appear possible, including along the front from eastern ND into northwestern MN, in the vicinity of the pre-frontal trough over the NE Panhandle vicinity, and south of the front across eastern MT. Development across eastern ND/northwestern MN and the NE Panhandle should progress southeastward into the corridor of greater buoyancy. Even so, weak ascent and relatively warm mid-levels could limit both overall storm coverage and updraft longevity. That being said, vertical shear will be strong enough to support updraft organization and supercell structures with any deep updrafts. Steep low-level lapse rates and high cloud bases suggest strong gusts are the primary severe risk, but some isolated large hail is also possible. Widely scattered nature of the storms casts doubt regarding upscale growth into a coherent MCS, but several separate bowing clusters appear probable. Thunderstorm coverage is expected to remain isolated from central into eastern MT as well, with modest ascent attendant to a shortwave trough progressing through the northern periphery of the western CONUS ridging acting as the primary impetus for initiation. Predominantly outflow-dominant storm structures are anticipated, with strong gusts as the primary severe risk through the evening. Convective evolution is uncertain, but these storms could continue eastward through SD and NE overnight, reintensifying as they interact with the stronger buoyancy expected to be in place. In addition to strong gusts, large hail would be possible with these storms if reintensification occurs. ...Central/Southern Appalachians into the Piedmont... Early-morning satellite and regional radar imagery show a decaying MCS progressing across central KY, well ahead of weak cold front that extends from far northwest OH southwestward through far southeast MO and northern AR. This MCS is forecast to continue eastward throughout the day, moving through the central Appalachians and eventually central VA. The airmass over this region is very moist, with recent surface analysis sampling upper 60s dewpoints over the higher terrain and low to mid 70s farther east from central VA into the Carolina Piedmont. General expectation is for renewed thunderstorm development along the southern flank of the MCS, likely from far southeast KY into Middle TN. Some reintensification is also possible farther north over WV and downstream in northern/central VA, but buoyancy will be lower than farther south, suggesting predominantly muted/transient updrafts. Currently, the highest storm coverage appears most likely across far western WV, eastern TN, and western NC. Vertical shear will be weak, but moderate/strong buoyancy and steep low-level lapse rates will still support the potential for damaging gusts. These strong outflows could promote the development of several forward-propagating line segments, where updrafts/downdrafts along the outflows could result in additional damaging gusts. ...Oklahoma/Arkansas... An MCS continues to progress eastward into northeast OK this morning, with a well-defined MCV noted in radar imagery back across far northwest OK. An associated outflow boundary currently arcs from the leading edge of the MCS in Osage County back southwestward through southwest OK. This MCS is forecast to weaken as it progresses eastward this morning, with weakening outflow also moving southeastward. A composite outflow/cold front will likely extend from southern OK into central AR this afternoon. Low-level convergence near this boundary will likely result in widely scattered thunderstorms by the late afternoon. Vertical shear will be weak, limiting storm organization. However, moderate instability, high cloud bases, and steep low-level lapse rates will still support the potential for isolated severe downbursts. ..Mosier/Dean.. 08/17/2026 $$