A complex severe weather forecast exists across the Upper Midwest today, with a potentially high ceiling on the event including a few strong tornadoes and significant damaging winds, but considerable uncertainty remaining around where this risk may be highest.
A weakening overnight thunderstorm complex is moving across northern Iowa into Wisconsin this morning, but the atmosphere is expected to recover behind it as warm, humid air surges northward through the day. One of the biggest forecast challenges will be determining how quickly the atmosphere can destabilize after the morning storms, making the exact location and timing of the greatest severe weather threat somewhat uncertain.
Despite those uncertainties, confidence remains high that conditions will become favorable for significant severe thunderstorms by late afternoon and evening. As a cold front approaches, any storms that develop should organize quickly into supercells thanks to strong wind shear and a very unstable atmosphere. The greatest risk for large hail and tornadoes is expected from Iowa across much of Wisconsin and into Upper Michigan. A few of the tornadoes could become strong if storms are able to remain isolated long enough before merging into larger clusters.
As the evening progresses, thunderstorms are expected to grow into clusters and sweep southeastward. While the threat for widespread damaging winds will increase during this phase, tornadoes and large hail may continue with the strongest storms before the severe weather gradually diminishes overnight. Anyone across the Upper Midwest should keep a close eye on forecast updates today, as the evolution of this morning's storms will play a major role in determining where the highest-end severe weather develops later this afternoon and evening.
