Day 1 Convective Outlook

This product has been superseded. View the updated product →

Issued: 2026-09-27 16:40 UTC  ·  Valid: 2026-09-27 16:30 – 2026-09-28 12:00 UTC

Summary

Isolated thunderstorms and lightning may occur in southeast New England, while a few thunderstorms are possible late this afternoon and evening from north Texas into southern Oklahoma. Overnight, elevated thunderstorms with the potential for isolated hail may move across western South Dakota into North Dakota.

Product Text

000 ACUS01 KWNS 271640 SWODY1 SPC AC 271637 Day 1 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1137 AM CDT Sun Sep 27 2026 Valid 271630Z - 281200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... CORRECTED TO REMOVE DUPLICATE TSTM AREA IN NEW ENGLAND ...SUMMARY... Organized severe storms are not expected through early Monday. ...Synopsis... An occluded cyclone will slowly weaken near the northern Mid-Atlantic coast, with lingering potential for elevated convection and isolated lightning flashes to its northeast across southeast New England. Farther west, weak ridging aloft will extend from the southern High Plains toward MN. A few thunderstorms will be possible late this afternoon/evening along a diffuse surface boundary from north TX into southern OK. The strongest storms may produce gusty outflow winds given steep low-level lapse rates with afternoon mixing, but the severe threat appears too low to justify adding severe-wind probabilities. Slightly elevated convection is ongoing across central SD in a zone of weak low-level frontogenesis, coincident with midlevel lapse rates near 8 C/km and MUCAPE close to 1000 J/kg. Deep-layer vertical shear is on the lower margins for storm organization, but it appears this convection has already peaked. Additional elevated thunderstorms are expected overnight from western SD into ND as low-level warm advection increases in association with embedded speed maxima downstream from a midlevel trough moving across CA/NV. While an isolated hail report could occur overnight as far northeast as southwest ND, the overall threat is low and when combined with the questionable threat for diurnal convection across the central High Plains, the MRGL area has been removed. ..Thompson/Chalmers.. 09/27/2026 $$