SPC Outlook: Slight Storm Risk Midwest

The Storm Prediction Center released its Day 1 Convective Outlook at 1:30 UTC on August 26, 2026, marking a slight risk of severe thunderstorms across the southern Great Lakes, Midwest, central and southern High Plains, Ozarks, Mid-South, and Lower Mississippi Valley. The main hazards are damaging winds, with large hail also a concern, particularly over the central High Plains.

Mid-South and Tennessee Valley

A mesoscale convective system (MCS) is moving southward and southeastward across western and middle Tennessee. The downstream airmass is heating and destabilizing, but vertical shear remains weak. Dewpoints in the mid-70s dominate the Mid-South and Lower Mississippi Valley, while middle Tennessee and northern Alabama have less low-level moisture. The outlook expects the MCS to continue, with new or stronger updrafts likely on the western flank where buoyancy is greatest. The lack of strong shear suggests an outflow-dominated mode with minimal organization, but sporadic damaging gusts are possible.

Arklatex and Southern Louisiana

A separate area of thunderstorm development is expected west of the MCS, with a surface low along the central Texas/Oklahoma border moving eastward into a moist, diurnally destabilized airmass. A weak mid-level cyclonic vortex (MCV) behind the low may augment ascent. Low-level convergence on a stalled frontal boundary across central Arkansas and a front approaching northern Arkansas could trigger additional storms. The outlook projects scattered to numerous thunderstorms, with modest deep-layer shear supporting multicell clusters. High total precipitable water and large buoyancy will fuel robust downbursts and potentially hail. Bowing segments may form, keeping isolated damaging winds possible across parts of southern Louisiana and Mississippi.

Southern Great Lakes and Midwest

Satellite imagery shows a well-defined shortwave trough moving across the Upper Great Lakes, with an occluded surface low over northwest Ontario and a secondary triple-point low over Upper Michigan. The system will shift eastward, bringing a cold front southeastward. Modest low-level moisture advection and heating ahead of the front create a corridor of moderate to strong buoyancy from central Illinois northeastward into southern Lower Michigan. Thunderstorm development is expected in this corridor. Low- and mid-level winds remain modest and veered, but 25-35 kt deep-layer shear will foster some updraft organization. Multicell clusters and marginal supercells pose hail and damaging wind threats, with wind risk increasing eastward as storms upscale. Veered low-level flow keeps tornado potential low. The severe threat will wane quickly as convection outruns moisture and nocturnal cooling stabilizes the boundary.

Central High Plains

Dewpoints in the upper 50s and low 60s characterize the central High Plains. Low-level upslope flow maintains moisture through the afternoon, while diurnal heating and steep mid-level lapse rates produce airmass destabilization and moderate buoyancy by late afternoon. The southern periphery of an enhanced north-westerly flow from the northern Plains brings 25-35 kt effective bulk shear. Late-afternoon thunderstorm development is expected, with isolated supercells possible. Hail is the primary risk initially, especially across the Colorado foothills, but clustering and more damaging wind potential are anticipated as activity spreads east-southeastward through the evening.

Southern High Plains

Mid-level flow and deep-layer shear are somewhat weaker than farther north. Convection that develops across central to eastern New Mexico may become loosely organized, posing an isolated threat for severe gusts due to a well-mixed boundary layer. This threat may extend into parts of the Oklahoma and Texas panhandles and west Texas through the evening before weakening.

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