Overview
- The Storm Prediction Center has run continuous mesoscale coordination and issued multiple mesoscale discussions while keeping severe-thunderstorm watches in place across the Plains, Midwest and Great Lakes into Saturday.
- Field observations tied to the evolving clusters include a measured 90 mph gust within an intense MCS in eastern South Dakota and a 72 mph gust near Mason City, Iowa.
- SPC products show the main hazard shifting from very large hail produced by early supercells to widespread damaging straight-line winds as storms cluster and develop rear-inflow jets.
- Forecasters warn that mesoscale features such as outflow boundaries, mesoscale vortices and nocturnal low-level jets are producing fast changes in timing and location, causing short-term weakening in some areas and re-development or downstream watch needs in others.
- Local warnings have already advised people in parts of southeast Wisconsin to shelter for roughly 60 mph gusts, and officials say residents should expect downed trees, power outages, and disrupted holiday travel if strong wind swaths pass over populated areas.