Mesoscale Discussion 1875 NWS Storm Prediction Center Norman OK 0227 AM CDT Sun Aug 09 2026 Areas affected...northeastern South Dakota and adjacent portions of Minnesota Concerning...Severe Thunderstorm Watch 545... Valid 090727Z - 090930Z The severe weather threat for Severe Thunderstorm Watch 545 continues. SUMMARY...Storms could gradually evolve into an organizing cluster, with some continuing risk for severe hail and, perhaps, increasing potential to produce strong to severe wind gusts through 3-5 AM CDT. DISCUSSION...Strong thunderstorm development has been focused within a narrow corridor east of Mobridge, aided by lift associated with low-level warm advection/frontogenesis, to the north/northeast of a weak surface low over central South Dakota. Forcing associated with a subtle short wave impulse digging within seasonably strong west-northwesterly mid/upper flow may also be providing support. As this perturbation progresses southeastward during the next few hours, the surface low is forecast to weaken with a gradual southward advancement of the near-surface frontal zone. Although storms are likely elevated above at least a shallow stable surface-based layer, they have been maintained by inflow of seasonably high moisture content supportive of large CAPE, beneath steep mid-level lapse rates associated with a plume of warm elevated mixed-layer air. This moisture, still largely concentrated over central/eastern South Dakota and Nebraska, is forecast to advect eastward in an evolving plume along the frontal zone across southern Minnesota/northern Iowa through 9-11Z. As it does, as least some convection allowing-guidance suggests potential for continuing upscale growth into an organizing cluster, which may eventually pose increasing potential to produce strong to severe surface gusts. ..Kerr.. 08/09/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...FSD...ABR... LAT...LON 45709909 45509774 44779624 44039656 43909765 44649925 45150006 45590027 45709909 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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