Mesoscale Discussion 1861 NWS Storm Prediction Center Norman OK 0439 AM CDT Sat Aug 08 2026 Areas affected...parts of west central Nebraska int southwestern/south central South Dakota Concerning...Severe potential...Watch unlikely Valid 080939Z - 081215Z Probability of Watch Issuance...20 percent SUMMARY...A period of rapidly intensifying thunderstorm development posing a risk for large hail appears possible by 5-7 AM CDT. Due to the relatively isolated, and perhaps short-lived, nature of the threat, it is not clear that this will require a severe weather watch, but trends are being monitored. DISCUSSION...Downstream of a subtle perturbation migrating around the northern periphery of prominent mid-level ridging centered over the southern Great Basin, large-scale ascent appears to be in the process of increasing across the South Dakotas Badlands vicinity through Nebraska Sandhills. This is being aided by lower/mid-tropospheric warm advection, as veering and strengthening flow in lower-levels (including to 30-40 kt around 850 mb) begins to support a rapid return of low-level moisture above a relatively cool/stable surface-based layer. Forecast soundings, including latest Rapid Refresh guidance, indicate that moistening near the initially dry base of the elevated mixed-layer air is contributing to strong destabilization, including CAPE increasing in excess of 2000 J/kg. With pronounced veering of winds with height contributing to strong deep-layer shear, the environment is becoming increasingly conducive to the development of supercells capable of producing large hail. Based on convection-allowing and related output, and trends in latest infrared satellite imagery, it appears that at least a few storms may rapidly initiate during the 10-12Z time frame. It is not clear how long this threat will continue after daybreak, due to some combination of upscale convective growth, continued warming (and increasing inhibition) aloft, and weakening of the nocturnal low-level jet. ..Kerr/Smith.. 08/08/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...UNR... LAT...LON 43940163 43129981 41670016 41620135 43300220 43940163 MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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