Overview
- The outbreak began July 2 with discrete supercells in the northern Plains that often grew into bowing clusters and mesoscale convective systems, and by July 4 storms had migrated into the Mid‑Atlantic and Northeast keeping multiple severe‑thunderstorm watches in effect.
- Observers measured extreme gusts during the Plains phase, including reported winds near 90 mph in eastern South Dakota, and clusters later produced widespread damaging straight‑line gusts in the Upper Midwest and Mid‑Atlantic.
- SPC and local NWS offices issued and maintained many mesoscale discussions and watches on July 2–4, using probability language (roughly 20%–95%) to reflect rapidly changing convective modes and where additional watches might be needed.
- Environmental analyses show very strong instability (MLCAPE/MUCAPE often 2,000–4,000+ J/kg), steep mid‑level lapse rates and 30–50 kt mid‑level flow, conditions that support long‑lived supercells, very large hail early on and later intense wind swaths as systems upscale.
- Forecasters warn the main short‑term hazards are damaging winds, localized large hail and heavy rain that could cause flash flooding; residents in watch areas should monitor local NWS warnings and seek sturdy shelter if storms approach.