Overview
- Storms that began as discrete supercells on July 2 organized into clusters and cold-pool-driven mesoscale convective systems that produced both very large hail and broad swaths of damaging straight-line wind.
- The Storm Prediction Center and local NWS offices issued repeated mesoscale discussions and multiple Severe Thunderstorm Watches to cover the eastward-moving threat from eastern South Dakota into Minnesota, Iowa and Nebraska.
- High-impact surface observations confirmed the threat, including a measured 72 mph gust near Mason City, Iowa, and gusts up to about 90 mph within a compact MCS in eastern South Dakota.
- Forecasters reported a general weakening trend overnight as the line moved into more stable air, but they warned isolated pockets of damaging wind and large hail could persist and said watch areas would be monitored for extensions or localized warnings.
- Meteorologists pointed to very large instability (MLCAPE often 2000–4000+ J/kg), mid-level flow and shortwave support as the cause of organized storms, and they coordinated with local forecast offices and river centers to manage short-term threats to people and infrastructure.