Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
628 ACUS02 KWNS 101751 SWODY2 SPC AC 101750 Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1250 PM CDT Wed Jun 10 2026 Valid 111200Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THURSDAY INTO THURSDAY NIGHT ACROSS PARTS OF SOUTHERN AMD EASTERN IOWAS....NORTHEASTERN MISSOURI....NORTHERN AND CENTRAL ILLINOIS...SOUTHERN WISCONSIN...NORTHERN INDIANA AND CENTRAL AND SOUTHERN LOWER MICHIGAN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THURSDAY AFTERNOON ACROSS THE ALLEGHENY MOUNTAINS THROUGH NORTHERN MID ATLANTIC VICINITY... CORRECTED FOR A FEW TYPOS/WORDING ...SUMMARY... Strong to severe thunderstorm development, including one or two organizing clusters, will probably be accompanied by the potential for large hail, damaging wind gusts and perhaps a couple of strong tornadoes in a corridor across the Midwest into Great Lakes region Thursday through Thursday night. ...Discussion... Models indicate that mid-level subtropical ridging will be maintained across much of the southern tier of the U.S. through this period, while the westerlies begin to trend a bit more zonal across the northern tier, in the wake of a broad, deep occluding cyclone slowly migrating northeastward toward southwestern Hudson Bay. A significant short wave trough turning to the east of the northern Rockies, to the south of the cyclone, at the outset of the period, is still forecast to pivot across southern portions of the mid Missouri Valley through the upper Great Lakes Thursday through Thursday night. This is likely to be accompanied by the northeastward migration of an associated secondary surface frontal low, from the central Great Plains across and northeast of the Upper Midwest/Great Lakes region by 12Z Friday. Downstream, mid-level ridging appears likely to build through the day across the lower Great Lakes/upper Ohio Valley vicinity, with one or two perturbations digging within weak northwesterly flow further downstream, across the Allegheny Mountains and northern Mid Atlantic vicinity. A seasonably moist air mass, supportive of moderate to large potential instability, is likely to be maintained within the warm sector of the cyclone, to the north of the subtropical ridge. However, it appears that this may be substantively modified, at least initially, by outflow from thunderstorm development today across a large portion of the Upper Midwest into Great Lakes region. There have been some adjustments of categorical and probabilistic thunder/severe lines to account for associated uncertainties, and also attempt to better account for consensus of varying model output. ...Upper Midwest/Great Lakes into southern Great Plains... Downstream of the approaching short wave impulse and secondary low, low-level warm advection on the nose of a 40-50 kt southerly 850 mb jet may be providing support for an evolving convective cluster along/north of an outflow boundary across southwestern Iowa at the outset of the period. This may include storms with potential to produce severe hail, before perhaps becoming rooted in a destabilizing boundary layer while spreading with forcing across Iowa through southern Wisconsin/northern Illinois through Thursday afternoon. This could include increasing potential for convection capable of producing damaging wind gust and perhaps a few tornadoes. Thereafter, the primary forcing for stronger destabilization and lift to support strong/severe thunderstorm development seems likely to shift to the intersection of the trailing outflow/secondary surface low/cold front across southeastern Iowa by late afternoon. This may include supercell development initially, before convection grows upscale and organizes in the presence of strong low-level and deep-layer shear, then propagates into and across the lower Lake Michigan/Michigan vicinities through Thursday evening, with potential for strong, damaging wind gusts and tornadoes. Scattered additional strong/severe storm development is possible in the corridor of stronger pre-frontal instability, but weaker mid/upper support and shear, southwestward through portions of the southern Great Plains. ...Alleghenies/northern Mid Atlantic... Moderate to locally strong potentially instability probably will become sufficient to support widely scattered strong to severe thunderstorm development with potential to produce damaging wind gusts Thursday afternoon and evening. ..Kerr.. 06/10/2026 $$