Day 1 Convective Outlook
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Issued: · Valid: –
Summary
Severe thunderstorms capable of producing damaging wind gusts and hail are expected today, with the highest risk occurring from northern Illinois through the Ohio Valley and Appalachia. Parts of the northern Plains may also experience severe wind gusts and large hail during the afternoon and evening.
Product Text
000 ACUS01 KWNS 110502 SWODY1 SPC AC 110500 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1200 AM CDT Tue Aug 11 2026 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN ILLINOIS INTO THE OHIO VALLEY... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS...AND FROM IOWA TO VIRGINIA... ...SUMMARY... Severe thunderstorms with damaging wind gusts will be possible today from the eastern Iowa/northern Illinois vicinity into parts of the Ohio Valley and central Appalachians. Areas of severe wind gusts and hail will also be possible over parts of the northern Plains. ...IA to the Mid-Atlantic... A complex forecast scenario is expected today from IA into the Ohio Valley and adjacent Appalachia. More than one MCS may be ongoing at the beginning of the period. The first across IA/southern MN, and one further southeast across parts of the Midwest (exact location is uncertain, but most likely IN/OH). Possible early day convection across IN/OH will spread east/southeast across the Ohio Valley during the morning posing risk for strong gusts. This activity is likely to emerge across Appalachia, and eventually VA and the broader Mid-Atlantic during the afternoon/evening. How much destabilization will occur across VA and the Mid-Atlantic remains uncertain given prior convection the previous day and potential convective debris across the region. Some damaging wind potential could materialize if sufficient destabilization occurs during the afternoon. The anticipated MCS over IA/southern MN early in the forecast period is then expected to continue east/southeast across the Midwest, fueled by a very moist and strongly unstable boundary layer. Midlevel flow is forecast to be quite strong (by August standards), with forecast guidance suggesting 700 mb greater than 60 kt spreading across the Midwest through evening. While the exact evolution of a potential severe MCS moving across the Midwest is uncertain, it is possible the morning activity over IA will develop southeast along outflow across the Ohio Valley. Given the strong kinematic field and ample instability, if a well organized MCS is maintained from IA southeast into the OH Valley, a swath of damaging gusts (some 75+ mph) will be possible. ...Northern Plains... East/southeasterly flow along the surface trough is forecast to maintain 60s F dewpoints across the western Dakotas and parts of NE this afternoon. Steep midlevel lapse rates atop the relatively moist boundary layer, and strong heating will support a corridor of moderate to strong instability across the western Dakotas. Scattered storms are expected by early evening amid supercell wind profiles. Elongated hodographs favorable for splitting cells with an accompanying risk for large to very large hail are forecast. Isolated severe gusts also could occur. Given a lack of stronger low-level jet during the nighttime hours, it appears unlikely that upscale growth will occur, and convection is expected to wane with eastward extent overnight. ..Leitman/Moore.. 08/11/2026 $$