Day 1 Convective Outlook

Issued: 2026-09-12 00:30 UTC  ·  Valid: 2026-09-12 01:00 – 2026-09-12 12:00 UTC

Summary

Severe thunderstorms capable of producing large hail, damaging winds, and isolated tornadoes are expected through tonight across far eastern South Dakota and portions of Minnesota.

Product Text

000 ACUS01 KWNS 120030 SWODY1 SPC AC 120028 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0728 PM CDT Fri Sep 11 2026 Valid 120100Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER FAR EASTERN SOUTH DAKOTA INTO PORTIONS OF MINNESOTA... ...SUMMARY... Widely scattered severe thunderstorms capable of producing large hail up to two inches, damaging winds, and a couple of tornadoes will continue through the remainder of the evening into tonight from far eastern South Dakota into portions of Minnesota. Isolated occurrences of severe wind gusts and large hail remain possible over parts of the central Plains tonight. ...Upper Mississippi Valley into the central Plains... A broken band of thunderstorms has recently developed from far eastern SD into north-central MN within a relatively narrow instability axis preceding a surface cold front and dryline. The presence of steep mid-level lapse rates (per 00Z ABR sounding) atop boundary-layer dewpoints in the mid to upper 60s F is resulting in MLCAPE up to 1500-2000 J/kg. As mentioned above, the corridor of stronger instability and minimal capping is rather narrow longitudinally, which suggests the severe weather threat may remain somewhat limited spatially into tonight. The KFSD VWP is likely indicative of the ambient kinematic environment, which features 35-40 kt of deep-layer shear and relatively strong low-level shear, supportive of a supercell storm mode with the primary hazard being large hail up to two inches. Tornado potential will be conditional on the maintenance of semi-discrete supercells residing within the narrow axis of minimal convective inhibition. Damaging wind potential may tend to increase by late evening as thunderstorms evolve into line segments. Additional storms appear possible late this evening into tonight ahead of a southeastward-moving cold front over portions of eastern and central NE. Similar to locations to the north, a relatively narrow zone of minimal convective inhibition and moderate instability exists ahead of the front, which leads to uncertainty in the areal coverage and duration of the threat. Severe wind gusts will be the primary hazard with any surface-based storms that can become established, though isolated occurrences of large hail are also possible. ..Mead.. 09/12/2026 $$