Convective Outlook
— Day 3
Marginal Risk
Summary
Strong storms accompanied by at least some risk for severe weather appears possible across parts of the Northeast into Ohio Valley, and across parts of the north central Great Plains, Sunday into Sunday night.
Discussion
An initially notable mid-level low inland of the Pacific Northwest coast by 12Z Sunday is forecast to remain progressive through this period, though it may slowly begin to devolve into an open trough while accelerating across the northern U.S. Rockies in response to a short wave digging into northwestern portions of the Canadian Prairies. Within the downstream westerlies, models indicate that short wave ridging will build across the northern U.S. Great Plains and adjacent Canadian Prairies through the Upper Midwest/adjacent northwestern Ontario, while downstream troughing digs across Quebec through the lower Great Lakes region.
The primary surface cyclone associated with eastern troughing is forecast to migrate from northern Quebec into the Labrador Sea by late Sunday night. As it does, the trailing cold front probably will advance southeast of the lower Great Lakes region by late Sunday afternoon, before overspreading the northern Atlantic Seaboard through upper Ohio Valley by the end of the period. Westward through the Ohio and middle Mississippi Valleys into the central Great Plains, it appears that this front may stall near or just south of the stronger westerlies.
Parts Of Western New England Into The Ohio Valley ?
Models vary concerning the degree of pre-frontal destabilization and the extent to which this may coincide with strengthening of westerly flow in the 700-500 mb layer, downstream of the digging short wave trough. However, particularly to the lee of the lower Great Lakes toward the northern Mid Atlantic vicinity, it appears that forcing for ascent will become increasingly conducive to at least scattered thunderstorm development by or shortly after peak daytime heating. As this occurs, developing storms will probably be accompanied by at least some risk for damaging wind gusts before weakening Sunday evening.
North Central Great Plains/Middle Missouri Valley Vicinity ?
The degree to which cool/stable boundary-layer air remains entrenched across much of Nebraska into parts of northern Kansas, to the south of the westerlies and beneath a remnant plume of warm elevated mixed-layer air, remains unclear. Between the cool boundary layer, which may be relatively shallow, and the base of the capping elevated mixed layer, it does appear that a seasonably moist air mass retreating northward through the region will contribute to moderate to large CAPE.
Although notable spread exists within/among the various model output, there appears potential for at least isolated to widely scattered strong to severe storm development in moistening southeasterly low-level flow across and to the southwest of the Black Hills vicinity by late Sunday afternoon, with the approach of the short wave trough. Subsequent development eastward into the Great Plains remains more uncertain, but, by late Sunday night, stronger storm development seems most likely to focus on the nose of a strengthening southerly low-level jet, near the northeastern periphery of the plume of elevated mixed-layer air, across/northeast of the middle Missouri Valley. This may be accompanied by at least a risk for severe hail.
000 ACUS03 KWNS 110731 SWODY3 SPC AC 110730 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Fri Sep 11 2026 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY INTO SUNDAY NIGHT ACROSS A CORRIDOR FROM WESTERN NEW ENGLAND THROUGH THE UPPER OHIO VALLEY AND ANOTHER CORRIDOR FROM NEAR AND SOUTHWEST OF THE BLACK HILLS THROUGH PORTIONS OF THE MIDDLE MISSOURI VALLEY... ...SUMMARY... Strong storms accompanied by at least some risk for severe weather appears possible across parts of the Northeast into Ohio Valley, and across parts of the north central Great Plains, Sunday into Sunday night. ...Discussion... An initially notable mid-level low inland of the Pacific Northwest coast by 12Z Sunday is forecast to remain progressive through this period, though it may slowly begin to devolve into an open trough while accelerating across the northern U.S. Rockies in response to a short wave digging into northwestern portions of the Canadian Prairies. Within the downstream westerlies, models indicate that short wave ridging will build across the northern U.S. Great Plains and adjacent Canadian Prairies through the Upper Midwest/adjacent northwestern Ontario, while downstream troughing digs across Quebec through the lower Great Lakes region. The primary surface cyclone associated with eastern troughing is forecast to migrate from northern Quebec into the Labrador Sea by late Sunday night. As it does, the trailing cold front probably will advance southeast of the lower Great Lakes region by late Sunday afternoon, before overspreading the northern Atlantic Seaboard through upper Ohio Valley by the end of the period. Westward through the Ohio and middle Mississippi Valleys into the central Great Plains, it appears that this front may stall near or just south of the stronger westerlies. ...Parts of western New England into the Ohio Valley... Models vary concerning the degree of pre-frontal destabilization and the extent to which this may coincide with strengthening of westerly flow in the 700-500 mb layer, downstream of the digging short wave trough. However, particularly to the lee of the lower Great Lakes toward the northern Mid Atlantic vicinity, it appears that forcing for ascent will become increasingly conducive to at least scattered thunderstorm development by or shortly after peak daytime heating. As this occurs, developing storms will probably be accompanied by at least some risk for damaging wind gusts before weakening Sunday evening. ...North central Great Plains/Middle Missouri Valley vicinity... The degree to which cool/stable boundary-layer air remains entrenched across much of Nebraska into parts of northern Kansas, to the south of the westerlies and beneath a remnant plume of warm elevated mixed-layer air, remains unclear. Between the cool boundary layer, which may be relatively shallow, and the base of the capping elevated mixed layer, it does appear that a seasonably moist air mass retreating northward through the region will contribute to moderate to large CAPE. Although notable spread exists within/among the various model output, there appears potential for at least isolated to widely scattered strong to severe storm development in moistening southeasterly low-level flow across and to the southwest of the Black Hills vicinity by late Sunday afternoon, with the approach of the short wave trough. Subsequent development eastward into the Great Plains remains more uncertain, but, by late Sunday night, stronger storm development seems most likely to focus on the nose of a strengthening southerly low-level jet, near the northeastern periphery of the plume of elevated mixed-layer air, across/northeast of the middle Missouri Valley. This may be accompanied by at least a risk for severe hail. ..Kerr.. 09/11/2026 $$