Day 3 Convective Outlook

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Issued: 2026-09-12 07:15 UTC  ·  Valid: 2026-09-14 12:00 – 2026-09-15 12:00 UTC

Summary

Marginal risk of severe thunderstorms is possible late Monday through Monday night across parts of the central Great Plains into the Upper Midwest.

Product Text

000 ACUS03 KWNS 120715 SWODY3 SPC AC 120714 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0214 AM CDT Sat Sep 12 2026 Valid 141200Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE MONDAY INTO MONDAY NIGHT ACROSS PARTS OF THE CENTRAL GREAT PLAINS INTO UPPER MIDWEST... ...SUMMARY... Strong thunderstorm development, accompanied by at least some risk for severe weather, appears possible across parts of the central Great Plains into Upper Midwest late Monday through Monday night. ...Discussion... Downstream of weak mid/upper troughing continuing to slowly dig across the Pacific coast, models indicate that mid/upper ridging (centered across the Southeast) may become increasingly prominent across the southern Great Plains into the lower Great Lakes and northern Mid Atlantic Seaboard through this period. To the north of this ridging, and in advance of a short wave impulse digging through the Canadian Prairies, a notable remnant mid-level cyclonic circulation is forecast to accelerate more rapidly east-northeast of the northern U.S. Rockies, across the international border into northwestern Ontario by late Monday night. It appears that this will be accompanied by modest surface cyclogenesis, and considerable strengthening of south to southwesterly lower/mid-tropospheric wind fields across much of the northern U.S. Great Plains through Upper Midwest/Great Lakes region. While an associated increase in vertical shear will contribute to an environment conditionally supportive of organized severe weather potential, destabilization within the warm sector remains much more uncertain. There does remain a general consensus among the various model output that a northward retreating near-surface baroclinic zone may provide the primary focus for stronger convective development, generally near the southern fringe of the westerlies, from parts of eastern Nebraska northeastward toward the Upper Midwest. However, even if the maintenance of a relatively cold, stable boundary layer along this zone, as depicted in the latest NAM forecast soundings, is too extreme, it remains unclear the extent to which thermodynamic profiles will become conducive to the risk for severe weather. ..Kerr.. 09/12/2026 $$