Day 1 Convective Outlook
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Issued: · Valid: –
Summary
Isolated severe thunderstorms are possible this afternoon across parts of the western Dakotas, which may bring marginally severe hail and wind gusts through the early evening.
Product Text
000 ACUS01 KWNS 231624 SWODY1 SPC AC 231622 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1122 AM CDT Wed Sep 23 2026 Valid 231630Z - 241200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE WESTERN DAKOTAS... ...SUMMARY... Isolated severe thunderstorms are possible this afternoon across parts of the western Dakotas. ...Western Dakotas... Recent surface analysis placed a low over far southeast MT, with a lee trough extending southward from this low across the High Plains into far West TX. A plume of moderate low-level moisture exists just east of this troughing, with upper 50s dewpoints currently reaching into southwest SD and mid 50s into western ND. This lee trough will help facilitate the maintenance of this moisture plume as the shortwave trough currently moving through WY and eastern MT continues northeastward into the region today and tonight. Widely scattered thunderstorms are forecast to develop as convective inhibition erodes in the vicinity of the lee trough and the Black Hills this afternoon. Strengthening southwesterly flow aloft will result in moderate deep-layer vertical shear (i.e. 30 to 40 kt from 0-6 km) amid 500 to 1000 J/kg of MLCAPE. This shear may aid in some storm organization potential, with the stronger thunderstorms perhaps yielding an isolated risk for marginally severe hail/gusts through early evening. ...Southern Appalachians... Recent visible satellite imagery shows widespread low stratus across both the Mid-Atlantic/Carolinas and farther east over much of the TN Valley. There is corridor between these regions from roughly northwest GA across far eastern TN/far western NC into far western VA where less low-level cloud cover is in place, replaced by more vertically developed structures. Temperatures in this region range from the upper 70s across northwest GA to the upper 60s/low 70s across far western VA. There is also slightly greater low-level moisture in this region (i.e. low 70s dewpoints), and these thermodynamic conditions are supporting modest buoyancy. This buoyancy explains the deeper clouds and recent lightning that has been observed in eastern TN. Thunderstorm activity will likely persist in this region throughout the day, supported by large-scale ascent attendant to an approaching shortwave trough and mesoscale convergence on an inverted surface trough that extends from southern AL into the southern KY/VA border vicinity. Some increase in the mid-level flow is anticipated as the shortwave moves through, but modest buoyancy and a mostly cluster multicellular mode should keep severe potential low. As such, removed the 5% wind probabilities across the region. ..Mosier/Gleason.. 09/23/2026 $$