Severe Weather Threat for Iowa: Strong Tornadoes, Large Hail, and Damaging Winds Possible
A significant severe weather event is expected to impact Iowa later today into tonight. The Storm Prediction Center has placed northern Iowa under a Moderate Risk (Level 4 of 5) for severe thunderstorms, highlighting the potential for strong to intense tornadoes, very large hail, and damaging wind gusts. This threat will primarily target northern Iowa, but some risk extends into central Iowa as well, especially if isolated storms can form farther south.
This setup is driven by a powerful storm system currently moving across the central United States. A strong surface low over South Dakota is pulling warm, moist air northward into Iowa. As the low tracks northeast into Minnesota by this evening, a warm front will lift north across the state, bringing increasing instability (fuel for thunderstorms) and very favorable wind profiles for rotating storms, known as supercells. Dew points are already rising into the 60s, and very strong winds aloft (a jet streak of 70-80 knots at 500mb) are setting the stage for explosive storm development.
Iowa Day 1 Tornado Risk: Yellow and red hatched areas represent a significant tornado threat.
Storms are expected to develop by late afternoon, roughly between 1–3 PM, first near the South Dakota/Minnesota/Iowa border. These storms will quickly move east and southeast across northern Iowa during the late afternoon and evening. The environment south of the warm front — which includes much of northern Iowa — will support the development of discrete supercells, the type of thunderstorms most capable of producing strong tornadoes and very large hail (golf ball size or larger). Wind shear will be strong enough that any storm able to stay isolated could rotate and become tornadic.
There is a chance that storms will eventually cluster into a line later tonight. If this happens, the risk for damaging straight-line winds will increase, but embedded tornadoes would still be possible within that line. Any discrete storms ahead of the main line this evening would have the greatest chance for strong or long-track tornadoes.
Farther south into central Iowa, the severe weather threat is a little more uncertain. While the atmosphere will be very unstable and supportive of severe storms, a cap — a layer of warmer air aloft that suppresses thunderstorm development — might prevent storms from forming unless strong forcing can break through it. If storms do manage to form in central Iowa, they could also become intense very quickly, producing large hail, damaging winds, and possibly tornadoes.
Residents across northern and central Iowa should closely monitor the weather today, have multiple ways to receive warnings, and be prepared to act quickly if a Tornado Warning is issued. Conditions favor rapidly developing and dangerous storms, particularly between late afternoon and midnight. Stay weather-aware, review your safety plans now, and be ready to seek shelter if needed.
