Day 1 Convective Outlook
This product has been superseded. View the updated product →
Issued: · Valid: –
Summary
Severe thunderstorms capable of producing large hail, damaging winds, and occasional tornadoes are expected late this afternoon and tonight across parts of the Upper Midwest. A marginal threat of severe hail and wind may also occur late this afternoon and evening across parts of the central Plains.
Product Text
000 ACUS01 KWNS 112002 SWODY1 SPC AC 112000 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Fri Sep 11 2026 Valid 112000Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE UPPER MIDWEST... ...SUMMARY... Scattered severe thunderstorms capable of producing large hail, (some 2+ inches), damaging winds, and a couple of tornadoes are expected late this afternoon and tonight across parts of the Upper Midwest. Thunderstorm development is more uncertain farther south into the central Plains, where a risk for large hail and severe gusts may exist late this afternoon into the evening. ...20Z Update... The ongoing forecast remains mostly on track with most areas remaining unchanged. Given the signal for the cold front to push into northern Kansas by early Saturday morning, along with at least a modest low-level jet, marginal wind/hail probabilities have been extended into more of central Kansas for the conditional potential of severe storms overnight. ..Wendt.. 09/11/2026 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Sep 11 2026/ ...Upper Midwest/central Plains... An eastward-progressive belt of quasi-zonal westerlies exists over the northern half of the CONUS, to the south of upper troughing over the Canadian Prairies/central Canada, and the east of the amplifying upper trough off the coastal Pacific Northwest. Weak frontal wave development will occur from eastern South Dakota into Minnesota as a cold front spreads eastward, with the front eventually overtaking a pre-frontal trough/dryline across the central Plains. A narrow corridor of 60s F surface dewpoints are in place ahead of the cold front/dryline, with diurnal heating aiding moderate destabilization along with steepened mid-level lapse rates. Minimal MLCIN is expected along/ahead of the front in far northeast South Dakota/western Minnesota into/just after peaking heating. Convective development appears likely in this time frame across this region, especially across Minnesota, owing to sufficient low-level convergence along the front coupled with forcing for ascent associated with the mid-level shortwave trough. Strongly veering and gradually strengthening winds with height through low/mid-levels, and 35-45 kt of deep-layer shear will easily support organized convection. Initial supercells should pose a threat for large hail (isolated 2+ inches possible), but convective mode will probably trend towards clustering fairly quickly given the presence of the cold front and strengthening low-level jet this evening. Any supercells that can remain at least semi-discrete into the early evening may also have a tornado threat with greater low-level shear forecast in this time frame. Scattered severe/damaging winds should occur with any clusters or bowing line segments that can develop and spread eastward through the evening. However, the wind threat will likely wane with eastward extent across Minnesota into western Wisconsin by late this evening given the narrow zone of destabilization forecast. Farther southwest, convective initiation and overall thunderstorm coverage from southeast South Dakota/southwest Minnesota southwestward into Nebraska and northern Kansas are more uncertain and probably more limited/conditional late this afternoon and evening, as the better forcing for ascent with the shortwave trough will remain regionally focused to the north. Still, a favorable thermodynamic environment and sufficient (25-35 kt) deep-layer shear would conditionally support severe hail/wind with any thunderstorms that can develop and be sustained. ...Mid-South/Tennessee Valley/Carolinas and Virginia... Multiple convectively augmented mid-level perturbations remain evident at midday in satellite/radar imagery, including over the Ozarks as well as the middle Gulf Coast in vicinity of southern Alabama. A stalled surface front extending from the ArkLaTex east-northeastward into the Tennessee Valley and Virginia will provide a focus for thunderstorms. Generally speaking, expectations are for generally disorganized/pulse-type convection to pose a threat for occasional damaging winds as diurnal heating destabilizes the boundary layer and steepens low-level lapse rates. However, a modest enhancement to mid-level flow across parts of the Mid-South (25 kt mid-levels per Little Rock AR WSR-88D VWP), as well as Virginia, could promote a couple of loosely organized clusters with a bit more of a focused damaging wind threat. $$