Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
047 ACUS03 KWNS 160731 SWODY3 SPC AC 160730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Wed Sep 16 2026 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE FRIDAY AFTERNOON AND EVENING ACROSS PARTS OF NORTHWESTERN KANSAS...SOUTH CENTRAL AND EASTERN NEBRASKA...ADJACENT SOUTHEASTERN SOUTH DAKOTA ...WESTERN AND CENTRAL IOWA... ...SUMMARY... Strong thunderstorms may impact portions of the central Great Plains through southern portions of the middle Missouri Valley late Friday afternoon and evening, accompanied by at least some risk for severe weather. ...Discussion... A vigorous short wave trough in the westerlies is forecast to dig across the northern Atlantic Seaboard accompanied by significant surface cyclogenesis near and east of the Canadian Maritimes. In the wake of the cyclone, it appears that a cold front will continue advancing offshore and through the southern Mid Atlantic Seaboard. A trailing low-level baroclinic zone may remain more or less quasi-stationary across the lower Ohio and lower/mid Missouri Valleys into northern high plains, beneath a weaker belt of westerlies in the southern mid-latitudes. Within this regime, a mid-level trough and embedded low are forecast to slowly progress across the Intermountain West through Rockies vicinity, preceded by a more subtle perturbation crossing the middle Missouri Valley. The latter impulse, and another westward migrating wave across the Florida Peninsula vicinity may contribute to further suppression of persistent mid-level ridging, which may otherwise maintain a considerable influence across a shrinking corridor centered across the southern Great Plains through Tennessee Valley. ...Central Great Plains through southern Mid Missouri Valley... Convective potential remains uncertain for Friday through Friday night. However, latest model output suggests that the mid-level perturbation overspreading the middle Missouri Valley will be accompanied by a moderate jet including 30-40 kt southwesterly flow in the 850-700 mb layer overspreading the central Great Plains through upper Mississippi Valley. As insolation contributes to a more strongly heated and deeply mixed boundary layer along modestly deepening surface troughing coincident with the low-level jet axis, there may be sufficient moisture to support scattered thunderstorm development capable of producing a few strong downbursts across parts of northwestern Kansas through south central Nebraska late Friday afternoon and evening. Closer to a weak developing frontal wave near the Missouri River, roughly between Omaha and Sioux City, seasonably high boundary-layer moisture content along a warm frontal zone to its south may support a corridor of sizable CAPE and potential for much more vigorous thunderstorm development. Lower/mid-tropospheric inhibition might remain an issue concerning boundary-layer based thunderstorm development, but a late afternoon/early evening supercell and small upscale growing cluster do not appear out of the question, before storms become elevated while spreading southeastward through portions of central Iowa during the evening. ..Kerr.. 09/16/2026 $$